A Workshop on

Liquids and Disordered Materials Science at

the Spallation Neutron Source

16-17 October 1998

Intense Pulsed Neutron Source, Argonne National Laboratory

Co-sponsored by Argonne and Oak Ridge National Laboratories

Co-chairs D. L. Price (ANL) and B. K. Annis (ORNL)



Compiled by T. Habenschuss (ORNL)
4 Nov 1998, Version 1.0

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Table of Contents

Introduction

Why neutrons?

Impact of increased flux at the SNS on liquids and disordered material science

Potential liquid and disordered materials research to be conducted at the SNS

Scientific case for a liquid/amorphous diffractometer - overview

Liquid/amorphous diffractometer specification

Other instruments

Appendix A. Current And Potential Research to Be Conducted at the SNS by the Liquids and Disordered Materials Science Community

Appendix B. Organizing Committee

Appendix C. Workshop Agenda

Appendix D. List of Workshop Participants

Acknowledgments



Introduction (Back)

The construction of a 1MW pulsed neutron source, the Spallation Neutron Source (SNS), at Oak Ridge National Laboratory, provides a unique opportunity to advance the science of liquids and disordered materials in the US. The purpose of this report is to survey the new research that will be enabled by this world class facility, and to lay out the instrumental needs of the scientific community engaged in the study of liquids and disordered materials. To this end a Disordered Materials Workshop, sponsored by ORNL and ANL, was held on 16-17 October 1998. This document is the outgrowth of this workshop.

The field of liquids and disordered materials ranges widely from low density fluids (supercritical state), through liquids, melts, solutions, glasses, amorphous materials, to semicrystalline solids. The materials of interest can be characterized by some degree of ordering short of the perfect crystalline state. It is precisely the short to intermediate range order that is the focus of this field of science, both of fundamental interest and from a practical point of view. The understanding of the structure and dynamics of non-crystalline materials has lagged behind that of crystalline materials due to the limited order encountered in the former. Yet many of the materials of technological utility depend on the nature of disorder found in these materials - for example, polymers, amorphous semiconductors, chemical process systems, oil recovery, supercritical solvents in "green chemistry" applications, etc.

The materials of interest may be in the form of bulk samples, films, fibers, and materials in confined environments. The length scales covered include local, short range atomic/molecular order on the few Ångstroms scale, intermediate range order (intermolecular correlations, networks in glasses, etc), to mesoscopic dimensions of 10's to 100's of nanometers (surfactant ordering, protein folding, liquid crystals, etc.). The dynamics of interest range from local, atomic/molecular motions to collective phenomena in, for example, glass transitions. Parameter space includes temperature, pressure, magnetic and electric fields, and dynamic conditions (flow, shear, pulsed deformation).

The two primary areas of experimental research are the structure and dynamics of disordered materials. In this report we focus on those experimental techniques where neutrons provide unique advantages over other structural and spectroscopic tools. We emphasize those studies which can not be done with present facilities and will benefit from the large increase in power represented by the SNS. The community employs neutron scattering techniques (liquid/amorphous diffractometers, including anomalous scattering and polarization analysis), spectrometers (inelastic, quasi-elastic), SANS, reflectometry, and texture measurements. Except for the liquid/amorphous diffractometer, these techniques are being addressed by other focus groups for the SNS, and we will only briefly outline our needs from the liquid and disordered materials perspective. Appropriate input will be given to the focus groups concerned with specifying these instruments. However, the liquid/amorphous diffractometer is unique to this community, and we will focus the report on its specification. In what follows we will list the characteristics of neutrons and the impact of increased flux from the SNS; state the scientific opportunities in liquids and disordered materials science; give a detailed specification of a liquid/glass diffractometer (L&AD), and the needs of the community for other experimental beamlines.



Why neutrons? (Back)

There are a number of advantages to neutrons as a probe of materials[1]. Some of these are unique, while others complement experimental techniques such as X-ray scattering.



  1. energies of thermal neutrons matched to atomic motions
    1. from neV of polymer reptation, to molecular vibrations and lattice modes, to eV transitions within electronic structures of materials


  2. wavelengths of thermal neutrons matched to atomic/molecular dimensions
    1. structural info from 10-5 to 104Å length scales (wave function of hydrogen to macromolecules)


  3. neutrons see nuclei, complementing X-rays, which see electron clouds
    1. neutrons sensitive to atomic correlations directly
    2. scattering cross section not a monotonic function of atomic number
      1. see light atoms (H, Li, N, O, etc.)
      2. possibility of distinguishing neighboring elements
    3. cross section varies among isotopes
      1. isotopic substitution (separate out correlations)
      2. contrast variation (highlight or eliminate parts of system)
    4. cross section independent of momentum transfer, Q
    5. TOF scattering experiment gives data up to very high momentum transfer, Q


  4. neutron's magnetic moment suited to study of
    1. magnetic structures and magnetic fluctuations in materials


  5. neutrons perturb experimental systems only weakly
    1. obtain atom-atom correlations directly


  6. neutrons are highly penetrating and non-destructive
    1. probe complex, delicate biological materials; where X-rays might damage samples
    2. a bulk probe, where X-rays might only probe the surface
    3. investigate interior of materials; examine real industrial products
    4. materials containing heavy elements which might not be transparent to x-rays
    5. penetrate through complex environments (furnaces, cryostats, pressure cells)


  7. neutrons allow application of anomalous dispersion
    1. selected nuclei with resonances can be used to highlight correlations


Impact of increased flux at the SNS on liquids and disordered material science. (Back)

The quantum jump in flux available at the SNS over existing neutron sources will result in higher resolution in space and time, measurements of weaker signals, over shorter time, on smaller systems, and in more extreme sample environments [1]. Of course, these impacts apply to all areas of neutron science.



  1. higher resolution in space and time
    1. accurate and precise structure refinements
    2. excitation spectra of complex systems
    3. dynamics of quasicrystals
    4. precise shapes of potential functions
    5. spectral studies of binding of molecules (chromophores, therapeutic biomolecules)
    6. excited state distortions of dissolved molecules in solution environments


  2. measure weaker signals
    1. smaller differences can be measured
      1. isotopic substitution studies; smaller differences in isotope cross-sections feasible (Carbon: molecular biology, biotechnology, pharmaceuticals, polymers)
    2. polarization analysis (separate coherent and incoherent signal)
    3. full spherical polarization analysis methods in magnetism
    4. subtle effects and small changes (high T superconductors)


  3. measurements over shorter time
    1. wider parameter space (T, P, electric and magnetic field, concentrations, pH, etc)
    2. solve problems rather than single experiments
    3. increase experimental throughput
    4. real-time studies:
      1. structure and dynamics of reaction species
      2. kinetic processes and material behavior under non-equilibrium conditions
      3. unit cost reduction - routine industrial exploitation


  4. measurements on smaller systems
    1. inherently small (crack tip strain distribution)
    2. only small amounts are available (new materials, isotopes)
    3. probe spatial variation
    4. structure and dynamics of surfaces and interfaces, thin layers
    5. lower concentrations (biomolecular concentration regimes)


  5. more extreme sample environments
    1. only small sample volumes possible (diamond anvil cell)
    2. environmental time is short (extremely low temperatures)


Potential liquid and disordered materials research to be conducted at the SNS (Back)

Examples of the structural research that might be tackled on the new spallation source can be divided into those requiring maximum flux and Q range, but modest resolution (mostly liquid materials), and those involving solid (glassy, amorphous or crystalline) materials, which require improved resolution to resolve details of the local structure. Traditionally, advances in this field have occurred whenever the available neutron fluxes are significantly enhanced, (e.g. when ILL started operation and then again when ISIS started operation). In all cases the examples represent extensions of work being carried out or planned at existing facilities: the advantages of the improved flux and/or resolution at the SNS mean that in every case these fields will progress to more complex materials and advanced sample environments, with particular emphasis on determining modifications to the structure induced by changes in the chemical or isotopic composition, temperature, pressure, or physical state of materials. (If carbon isotope substitution can be used, this would open up large areas of organic, macromolecular and biological systems).

Similarly, the increased flux from the new spallation source will impact the study of dynamics in such areas as vibrational motion in network inorganic glasses, polymers and soluble proteins, ion mobility in super-ionic glasses and conducting polymers, relaxation in bulk and interfacial water, boson peaks, and coherent inelastic process such as Brillouin scattering.

What follows is a partial list of topics which are currently of interest to the liquids and disordered materials community. Appendix A lists selected, short descriptions of specific research topics that are to be addressed at the SNS.



  1. Fundamental fluids
    1. quantum fluids - 3He, 4He, mixtures
    2. liquid hydrogen


  2. Molecular fluids and solutions
    1. hydrogenous liquids
    2. liquids under extremes of temperature and pressure
    3. compare to simulation; map out T/P parameter space
    4. supercritical solutions for environmentally benign chemistry
    5. non-aqueous electrolyte solutions


  3. Water and aqueous solutions
    1. especially at extreme T/P conditions - supercooled, supercritical
    2. structural and dynamic similarities between supercooled and interfacial water
    3. Brillouin spectroscopy of bulk and interfacial water


  4. Fluids in confined geometries
    1. liquids confined in, for example, Vycor or selfassembled mesoscopic materials
    2. fluid - membrane interactions


  5. Liquid and amorphous polymers and polymer blends
    1. local structure and motion, and effects of ions in electrolytes
    2. polymer structure and dynamics under shear
    3. intermolecular structure of polyolefins and blends; phase separation/miscibility
    4. local structure and its effect on electronic properties, including conducting polymers
    5. orientation in polymer fibers
    6. Amorphous fraction in semi-crystalline polymers
    7. mesophase transformations in semicrystalline polymers: conformational disorder


  6. Crystalline/liquid hybrid materials
    1. Intercalated liquids in e.g. graphite, clays
    2. liquid crystals


  7. Glasses, fundamental
    1. definition of basic structural units in glasses and the effect of modifiers on the distribution of bond lengths and angles
    2. effect of superstructural units on vibrational density of states in inorganic network glasses
    3. thermodynamic fluctuations at the glass transition
    4. fluctuations in chemical order in multicomponent glasses
    5. the crystallization process, pre-melting effects
    6. crystallization in production of glass ceramics
    7. orientational order in glass fibers
    8. nature of the boson peak in glasses as a f(T,P)
    9. understand the nature of "fragile" and "strong" glasses


  8. Hybrid glasses
    1. mixed oxides, polymer/inorganic glasses


  9. Fast ion conducting glasses
    1. Searching phase diagrams for the best electronic performance
    2. in situ study of battery materials e.g. charging/discharging
    3. thin films in electric fields
    4. use of QENS to investigate the mobility of conducting ions


  10. Semicrystalline materials
    1. crystalline materials with significant disorder
    2. non-crystalline materials with significant local order, e.g. graphite, clay-type materials, network silicas


  11. electronic processes in covalent systems such as oxides; includes ferroelectrics, metal/insulator transition, superconductivity and spin-lattice coupling


  12. Geologically relevant materials
    1. liquids and glasses of mixtures/solutions of lanthanide, actinide, alkali and alkaline earth silicates, phosphates and borates
    2. amorphisation of geological materials under extreme pressure


  13. Biologically relevant fluids
    1. hydration and conformation in organic materials of biological interest
    2. polyelectrolyte liquids
    3. location and interaction of biologically significant ions, e.g. Ca, Mg ions
    4. temperature dependence of biological fluids and solutions
    5. dynamics of caged or interfacial water in proteins, DNA, and membranes
    6. vibrational spectroscopy of surface residues on soluble globular proteins


  14. Metals and metallic alloys, semiconductors
    1. liquid metals and alloys
    2. metallic (amorphous) glasses
    3. diffuse scattering from chemical and positional disorder in alloys
    4. amorphous silicon fuel cells


  15. Molten salts
    1. molten carbonates for fuel cells


Scientific case for a liquid/amorphous diffractometer (L&AD)- overview (Back)

Currently the only dedicated facility within the US for neutron diffraction studies of the non-crystalline states of matter at the atomic length scale is GLAD at the IPNS pulsed neutron source, and the new source would provide an advancement in this capability by a factor of about 100. The factor 6 or more enhancement in flux compared to the existing ISIS source or the (upgraded) LANSCE source, will allow the possibility of constructing either a diffractometer whose resolution is equivalent to existing facilities, such as HIPPO at LANSCE, SANDALS at ISIS, or the D4B diffractometer at ILL, but whose neutron flux is dramatically higher than at those facilities, or else a diffractometer whose count rate is similar to the existing facilities, but whose resolution is double that currently available anywhere in the world for this kind of work. The latter instrument would be equivalent in resolution to the new GEM diffractometer currently under construction at ISIS, but with at least 6 times the count rate. The instrument specification outlined below allows for both possibilities, subject only to budget and engineering constraints. If budget restrictions prevent full realization of the concept described then the community would opt for the high count-rate, modest resolution option in the first instance, with adoption of the higher resolution option at a later stage.

The scientific case for a disordered materials diffractometer at the SNS derives from the fact that the US currently has NO world-class facility for studying the local atomic ordering in materials with neutrons.

Experience in Europe and Japan has shown that such a diffractometer is likely to be oversubscribed by a factor of 2 - 2.5. In addition, provided the correct infrastructure for gaining access to the facility is set up, that experience indicates that the User base will grow and evolve as new groups of materials scientists, chemists, geologists and biologists realize the new opportunities for research that the diffractometer will provide.

The field of diffraction from disordered matter has stringent requirements for detector stability and uniformity, detector shielding, beamline collimation, wave vector transfer (Q) range (with appropriate resolution in each range), and neutron flux in all Q-ranges. Such a specification has never been realized by any existing or proposed powder diffractometer used for crystallographic studies, and it is essential that a diffractometer dedicated to local structure studies should be a separate instrument at the SNS. User demand is likely to require this in any case.



Liquid/amorphous diffractometer specification (Back)

Experience at existing pulsed and reactor neutron sources gives very clear indications for the specification of a disordered material diffractometer at the SNS. A singular departure from existing facilities of this kind is the requirement for a very large range of Q values for the new instrument: typically 0.02Å-1 to 80Å-1 was felt to be the minimum that would be acceptable but still achievable with careful design. The specified minimum Q is an order of magnitude smaller than existing liquid & amorphous diffractometers, and is required to accommodate the increasingly complex materials that are being investigated by this method. This range should be enhanced further if the means could be found, possibly by inserting converging collimators in front of the sample. It was felt to be especially important that at low Q values there should be at least a decade of overlap with any SANS facility that was developed at SNS, to ensure that diffraction data on any materials that would require both L&AD diffractometer and SANS instruments could be satisfactorily merged.

Equally the maximum resolution for the research glasses and semicrystalline solids (about 0.25% in backscattering) would involve an unacceptable loss in count rate (about a factor of 6) for the research on liquids, where a more modest resolution (around 0.5% in backscattering) was needed. These different requirements could potentially be met in a single diffractometer, with two sample tank positions: the detector array would then be transported physically between the two positions, depending on the resolution required.

Moderator. Experience at existing pulsed neutron sources shows that a liquid methane-like moderator is nearly ideal for this work, providing useful flux over a wavelength range of at least 0.05Å to 4Å, while at the same time providing an acceptable pulse shape. For liquid hydrogen the long wavelength spectrum is enhanced, with poor pulse structure, making for substantial frame overlap problems at 60Hz, while for a water moderator the flux cuts off at too small a wavelength, around 2Å.

Choppers. T0 and frame overlap choppers might be needed for this instrument, depending on the moderator and flight path. Experience at existing pulsed sources does not yet say whether a T0 chopper improves the background on a diffractometer appreciably, and it has the disadvantage of limiting the minimum wavelength to around 0.2Å. By the time L&AD begins detailed design, the necessary tests will have been completed at ISIS. And additional information will be forthcoming from experience gained from the HIPPO instrument under construction at LANSCE.

Scattering Angles. There should be maximum solid angle coverage at all chosen angles to exploit the full capabilities of the SNS. The majority of liquids diffraction is best performed at low angles in the range 0 - 60 in order to minimize inelasticity corrections. Special sample environments and high resolution dictate that detectors at 90 and in backscattering geometry should be provided. The 90 detectors will also allow measuring Q perpendicular and parallel to aligned films. The backscattering detectors should be full cone, highly pixelated for texture measurements. These requirements mean that the instrument should be perpendicular to the moderator. (If anomalous scattering is to be performed, then the angular range should be continuous with no abrupt changes in resolution?)

Resolution. The table below lists the required resolutions (Q/Q) for the two instrument options.

2 Q-range Low resolution option High resolution option
0 - 5 0 - 1Å-1 ~5% ~5%
5 - 60 1 - 50Å-1 ~2 - 3% 2%
90 2 - 100Å-1 0.7% 0.4%
150 3 - 100Å-1 0.5% 0.25%

The low resolution option would be realized with a diffractometer at ~10 to 11 m from the target, while the high resolution option would require a minimum of 17m, subject to detailed moderator specification. These flight paths are dictated by the intrinsic pulse widths from the source: narrowing the pulse (by means of thin moderators for example) too much on a short flight path instrument to achieve better resolution throws away the enhanced flux that would otherwise be achieved at SNS and is therefore not acceptable.

Detectors and monitors. Although detailed design cannot be performed at this stage, several requirements are paramount to the success of the instrument and will require detailed study well ahead of the instrument being designed in detail. The detectors must be as efficient as possible, to exploit the high neutron energies available at SNS. They must be fast to accommodate the extremely high count rates (>1MHz) at short flight times. They must be stable in order to be able to exploit the high flux (0.1% drift in efficiency over 24 hours is a minimum requirement, but ideally should be better than this). And they must be insensitive to radiation. In addition suitable beam monitors will be needed before and after the sample position to monitor the flux incident on the sample, and the neutron attenuation by the sample, respectively. Detector development needs to begin very soon if SNS is to be viable by 2005.

Other aspects and data analysis. Numerous other aspects of the diffractometer will need to be specified, such as appropriate sample environment, beamline collimation and shielding, access to the sample position and data acquisition electronics. These are likely to be common to many SNS instruments, and will need to be considered across the facility. A particular requirement for this instrument is for a multiple position, temperature controlled, sample changer for rapidly moving between samples, in situations where the very highest resolution is required. A full range of standard equipment e.g. cryostats, furnaces, pressure, magnetic/electric fields, gas flow etc. Adjustable apertures should be provided on the incident beam, and converging collimators should be investigated as an option. These would be inserted when the very low Q-values are required. Equally important will be the provision of an appropriate, comprehensive and user-friendly data analysis package to assist users in interpreting their data.



Other instruments (Back)

There are a number of other instruments which are used by the disordered materials community with some frequency. Although these instruments are being championed by other focus groups, there should be input from the disordered materials community into the design of these instruments for the SNS. Some of these beamlines will be baseline instruments available on startup, others would be more appropriate for a second target station (indicated by *).

Small angle scattering.* The SANS instrument should have a Q-range from 0.001Å-1 to 2Å-1. There should be a decade in Q overlap between the 2 instruments with comparable resolution in the Q range spanning the first peak in S(Q) (say, 2 Å-1). Resolution in this region to be about 2%, which is essential for normalization between the two instruments.

Anomalous scattering. If anomalous scattering is not possible on the L&A diffractometer, then a chopper instrument with full angular coverage could be used in diffraction mode.

Inelastic instruments. The main requirement is for a chopper instrument for S(Q,w) measurements with an energy range up to several 100 meV with resolution better than 1%. It should have a full range of continuous angles and a low angle detector for Brillouin scattering.

Quasi-elastic scattering.* There could be many instruments in this category with energy resolutions ranging from 1µev to 50µeV each with a wide energy range. It might be best to concentrate on one instrument in the first instance. Perhaps this should be the one with 1µeV resolution. The instrument should have wide angular (Q) coverage with a dedicated small angle arrangement.

Spin-echo instrument.* This is also an attractive possibility for exploring such areas as the alpha relaxation and nanosecond motions in proteins.

Polarization. The community would like to be kept aware of developments in polarization analysis instruments. These would be used for example for separation of incoherent & coherent scattering.

Total scattering. The ability to use another instrument or beam line for transmission experiments in order to measure total cross-section would be useful.

Elastic diffraction. Inelastic instruments could also be used for measuring elastic diffraction by measuring at zero energy transfer.





References



  1. "ESS, A Next Generation Neutron Source for Europe", Vol II. The Scientific Case. John L. Finney, co-ordinator, University College London, March 1997.




Appendix A. Current And Potential Research to Be Conducted at the SNS by the Liquids and Disordered Materials Science Community (Back)



  1. The Intermolecular Hydrogen-Hydrogen Structure in Polymers from Neutron Diffraction (B. K. Annis, J. D. Londono, , A. K. Soper)


  2. Aqueous Solutions to High Temperatures and Pressures (J. M. Simonson, ORNL)


  3. Determination of Local Environment of Lithium Ions in a Polymer Based Electrolyte (B. K. Annis, ORNL, J. D. Londono, DuPont, J. Z. Turner, ISIS)


  4. Boson peaks in disordered materials (B. K. Annis, ORNL)


  5. Conducting polymers electrolytes (M-L. Saboungi, D. L. Price, ANL)


  6. Non-aqueous electrolyte solutions (W. S. Howells, RAL, ISIS)


  7. QENS In Bulk Supercooled and Interfacial Water (S.H. Chen, MIT)


  8. Neutron Brillouin Spectroscopy Of High-Frequency Collective Modes in Bulk and Interfacial Water (S.H. Chen, MIT)


  9. Dynamics of Bulk water under extreme conditions of temperature and pressure (M-C. Bellissent-Funel, Laboratoire Leon Brillouin)


  10. Role of water in biological macromolecules (M-C. Bellissent-Funel, Laboratoire Leon Brillouin)


  11. Super-ionic glasses (Lars Borjesson, Chalmers University of Technology)


  12. Vibrational density of states for network glasses (Adrian Wright, University of Reading)


  13. Geophysical materials: silicate liquids and glasses (M. Wilding, UC Davis)


  14. Microscopic Structure of 4He-3He Mixtures (P.Sokol, Penn State U)


  15. Collective Excitations in Confined Superfluid Helium (P. Sokol, Penn State U)


  16. PDF Analysis Applied to Disordered Crystals (T. Egami, University of Pennsylvania)


  17. Structured Ion Conductors (J. W. Zwanziger, Indiana University)


  18. Critical Micelle Conditions in Supercritical CO2 (H. D. Cochran, G. D. Wignall, ORNL, J. D. Londono, DuPont)


  19. Chain Molecules in Supercritical CO2 (H. D. Cochran, G. D. Wignall, Y. B. Melnichenko, ORNL)


  20. Chain Molecule Systems Under Shear (H. D. Cochran, H. J. Dai, ORNL, M. D. Dadmun, U. Tenn.)


  21. Structure Property Relations in Transition Metal Oxides (S. J. L. Billinge)


  22. Thermodynamics from diffraction (S. J. L. Billinge, P. G. Radaelli)


  23. Aqueous Electrolyte Solutions: Structural Studies (G. W. Neilson, Bristol)


  24. Local Structure Studies of Pi-conjugated and Other Unconventional Polymers (M. J. Winokur, University of Wisconsin-Madison; B.R. Mattes, Los Alamos National Laboratory)


  25. Glass Transitions (F. J. Bermejo, CSIC- Madrid) )

  1. The Intermolecular Hydrogen-Hydrogen Structure in Polymers from Neutron Diffraction (B. K. Annis, J. D. Londono, , A. K. Soper) -- Interchain interactions in amorphous polymers influence static quantities such as the cohesive energy density and miscibility as well as dynamic processes such as chain mobility and possibly the behavior of boson peaks. Neutron scattering experiments using H-D isotopic substitution permit the direct determination of the intermolecular H-H structure function hHH(Q) and the intermolecular H-H correlation function gHHinter(r) without recourse to models of the intramolecular structure. The method is unique for obtaining this kind of information in polymers and permits determination of the global "correlation hole" where gHHinter(r) < 1 for a considerable range, due to the screening of intermolecular correlations by intramolecular correlations. By suitable H-D substitution on side groups, the method can in principle probe the reduction in interchain correlation specific to these groups, i. e. the "local correlation hole". The resulting distribution functions provide stringent tests of molecular dynamics simulations and theoretical models. These studies require high intensity to obtain sufficient statistics in the difference function and very good detector stability. They also have detector placement requirements not available on typical powder diffraction instruments and beamlines optimized for scattering from hydrogenous liquid/amorphous materials. These needs argue for a liquid/amorphous diffractometer at the SNS.


  2. Aqueous Solutions to High Temperatures and Pressures (J. M. Simonson, ORNL) - The large qualitative changes in the behavior of aqueous solutions with increasing temperature are driven by changes in the local structure near solute particles (e.g., hydration or ion pairing) coupled with the strong increase in the compressibility of the solvent. Quantitative, predictive understanding of these phenomena, needed to model the behavior of these fluids in natural and technological environments, requires that these local structural and dynamic changes be measured precisely over wide ranges of state conditions (temperature, pressure, and composition). While the method of neutron diffraction with isotopic substitution has been shown to give the information needed under favorable conditions, progress is hindered by limitations of current facilities for the study of inherently low-contrast, high-background experiments such as dilute solutions in heavy-walled pressure vessels at high temperatures. New advances in experimental information available through the high flux of the SNS, coupled with a highly-stable, moderate-resolution diffractometer optimized for the study of short-range order in noncrystalline materials, will enable studies of additional elements having too little contrast for investigation on present facilities and will give the levels of precision and accuracy needed to develop and refine molecular-scale models and simulations of the properties of solutions under extreme conditions.


  3. Determination of Local Environment of Lithium Ions in a Polymer Based Electrolyte (B. K. Annis, ORNL, J. D. Londono, DuPont, ) -- Electrolytes, composed of lithium salts dissolved in a polymer, are currently considered to be candidates for battery development . The cation conduction mechanism in these rubbery materials is not well understood, and will depend on the local environment of the ion. The radial distribution function about Li+ has been determined by the single difference method, using two solutions of LiI in deuterated polyethylene oxide (PEO). The solutions were measured at a temperature of about 90oC at which point the substantial association of ether oxygens to Li+ is expected. The number of associated oxygen atoms was found to be similar to that in the crystalline phase. Studies of this type need to be carried out at a variety of temperatures and lithium ion concentrations and would benefit greatly from the high throughput available on a high intensity diffractometer. The effect of the ions on the polymer chain configuration can be determined by accurate measurements of radius of gyration which would be a SANS problem.


  4. Boson peaks in disordered materials (B. K. Annis, ORNL) -- A peak in scattered intensity in the range 1-5 meV in the vicinity of the glass transition and below it is known as the boson peak. The understanding of the origins of this peak is a matter of much exsperimental and theoretical investigation. Although it is a nearly ubiquitous phenomenon in disordered materials, the intensity, temperature dependence and position of the peak varies significantly with the specific material. Study of the boson peak requires spectra collected at several temperatures. In the case of the so-called "fragile" glass formers it is expected that pressure mapping of the peak position will also be of interest. The instrumental requirements are an energy resolution of 50 microeV, and energy range out to at least 10 meV and a Q range of 0.5-3.0 -1.


  5. Conducting polymers electrolytes (M-L. Saboungi, D. L. Price, ANL) -- Among ionic conducting materials, PEO mixed with various salts, is considered to be a typical solid polymer electrolyte with a number of potential technological applications such as advanced batteries, sensors and electrochromics. PEO can form complexes with various salts including those of alkali metals and alkaline earths. However their development has been somewhat hindered by the limited knowledge about their properties, especially the nature of their ionic conduction in terms of microscopic structure and dynamical behaviour. Neutron diffraction (with isotopic substitution) can elucidate the structure and QENS will then probe the dynamics, in particular the local chain motion and how it is affected by the ions.


  6. Non-aqueous electrolyte solutions (W. S. Howells, RAL, ISIS) - Non-aqueous solutions have applications in batteries , electro-deposition of metals, production of wet capacitors and in electro-organic synthesis. The solvents (such as dimethyl sulphoxide, acetonitrile and methanol) are important industrial solvents as well as being widely used in organic chemistry, fine chemical technology and biology (DMSO is a cryoprotectant for biological structures). These solutions are also a severe test for current theories due to the absence of quantitative information about the specific ion-molecular interactions and the influence of the ion on molecular dynamics, structure and strength of intermolecular interactions in solutions. Neutron diffraction with isotopic substitution will determine the structure and QENS will probe the dynamics of the protons in the hydrogenous solvent and investigate the changes with, for example, type of ion and concentration. The results can then be compared directly with molecular dynamics simulations.


  7. QENS In Bulk Supercooled and Interfacial Water (S.H. Chen, MIT) - Presence of "interfacial water" in proteins, DNAs and membranes plays a fundamental role in triggering the "slow dynamics" in these bio-macromolecules which makes various enzymatic and biological functions possible. There is a strong evidence that dynamics of the interfacial water is similar to a bulk supercooled water at a lower temperature. In bulk supercooled and interfacial water, the test-particle intermediate scattering function shows a two-step (fast and slow) relaxation with a plateau in-between. This plateau defines an incoherent Debye-Waller factor which is a measure of the size of the transient "cage" surrounding the water molecule. The fast relaxation decays in less than a ps and can be attributed to rattling motions of water molecules in the cage. These vibrations are harmonic with a density of states which has a two-peak structure. The slow relaxation is approximately stretched exponential having a relaxation time in the hundreds of ps or in ns (slow dynamics). High resolution QENS spectra are dominated by the slow relaxation which reflects largely the CM motions of water molecules following the structural re-arrangement of the cage. The resulting QENS line shape is non-Lorenzian. The QENS spectrometer should be designed with an optimal energy resolution in the several µV range in order to study the detail of the line shape. It should have a Q coverage of Qmin = 0.1 Å-1 and Qmax = 2.5 Å-1 in order to reach the diffusion limit at the lower end and to detect the Q-dependent shape of the D-W factor at the higher end.


  8. Neutron Brillouin Spectroscopy Of High-Frequency Collective Modes in Bulk And Interfacial Water (S.H. Chen, MIT) - Water shows an anomalous dispersion of sound waves at a q of about 0.3 Å-1, above which the sound speed increases by a factor two. In order to study the excitation, incident neutron energy has to be greater than 80 meV. The excitation persists up to at least q = 1.0 Å-1. INS spectrometer needs to have 0.5% energy resolution at 100 meV and a Q coverage of 0.1 -1 to 2.0 Å-1, in order to be competitive with IXS. The coherent Rayleigh-Brillouin triplet at the above mentioned q range consists of a strong central peak and a weak side wings, which are due to the existence of the high-frequency sound. In order to study the spectral width and shape of the central peak, one needs to use a spin echo type spectrometer with a time range of 1 ps to 20 ns. This is because the alpha-relaxation process, which gives rise to the central peak, has a relaxation time which show a strong q-dependence.


  9. Dynamics of Bulk water under extreme conditions of temperature and pressure (M-C. Bellissent-Funel, Laboratoire Leon Brillouin) - This research activity is in relation with the structural studies of water that has been investigated in a wide range of temperatures and pressures. Some information about the degree of hydrogen bonding is now available: in supercritical states -- M-C. Bellissent-Funel et al., JCP, 107, 2942 (1997), T. Tassaing et al., Europhys. Let., 42, 265 (1998); in supercooled states : M.-C. Bellissent-Funel et al., JCP, 102, 3727(1995), M.-C. Bellissent-Funel, Europhys. Let, 42, 161 (1998). There is a big interest to study dynamics of water by quasielastic neutron scattering for the same pressures and temperatures. The whole structural and dynamics information about water as functions of temperature and pressure could allow to access to the more reliable potential among the various water potentials that are presently available.


  10. Role of water in biological macromolecules (M-C. Bellissent-Funel, Laboratoire Leon Brillouin) - An important field of research in protein biophysics concerns the role of water on the structure, dynamics and function of globular protein. Both the effect of water on internal protein motions and the effect of protein on surrounding water dynamics are of primary concern in these studies.
    1. Dynamics of Water at Model Interfaces - hydrophilic surfaces such as silica surface (porous Vycor glass). From structural and dynamic studies by neutron scattering, there is a strong evidence that surface water behaves like a bulk supercooled water, M.-C.Bellissent-Funel et al, JCP, 98, 4246 (1993) (Structure), M.-C.Bellissent-Funel et al, PRE, 51, 4558 (1995). The single particle motions are now analyzed in terms of the alpha relaxation dynamics predicted by mode coupling theory of supercooled liquids, J.-M. Zanotti et al, PRE (1998).
    2. Dynamics of Water at surface of a protein. Some similar results are obtained at the surface of a deuterated C-phycocyanin protein., M.-C.Bellissent-Funel et al, Faraday Discuss.,103, 281, (1996), S. Dellerue et al, to be published.
    3. Dynamics of proteins at different time scales. Quasielastic and inelastic neutron scattering allows the investigation of motions ranging from subpicoseconds to nanoseconds. That can be achieved by changing the resolution of the instruments. Vibrational motions, picosecond diffusion motions of surface residues have been observed in soluble globular proteins such as C-phycocyanin, parvalbumin, lyzozyme as well as in membrane proteins. Nanosecond motions in the same proteins are under investigation by neutron spin-echo technique (Thesis of S.Dellerue in preparation).


  11. Super-ionic glasses (Lars Borjesson, Chalmers University of Technology) - Super-ionic glasses are solid materials where some ionic species are mobile within an otherwise frozen glassy network. These materials are thus of highest interest for electrochemical applications as solid electrolytes e.g. in solid-state batteries, sensors or smart-windows. These glasses also represent a challenge from a more fundamental point of view. The mechanism behind the high conductivity in this material is far from trivial and despite extensive research for the last decades there is no macroscopic theory explaining the conduction process. the development of new materials is so far based on experience and common practice rather than on fundamental understanding of the materials. Neutron diffraction has already established that these glasses have an expanded structure leading to conduction pathways. QENS is then able to investigate the mobility of the conducting ions.


  12. Vibrational density of states for network glasses (Adrian Wright, University of Reading) - An investigation of the sharp features in the vibrational density of states for network glasses arising from superstructural units and other small planar rings, including the Q-dependence (as an aid to their interpretation). N.B. A quantitative study cannot be performed by Raman Spectroscopy, due to unknown and large matrix element effects. From the point of view of inorganic network glasses, the greatest step forward in inelastic scattering instrumentation at ISIS has been the MARI spectrometer since, for the first time, this has the resolution necessary to investigate the sharp peaks arising from superstructural units (e.g. boroxol and triborate groups) in borate glasses and the sharp lines in other systems resulting from small planar rings, of the type investigated by Frank Galeener using Raman scattering. It also has a wide angle coverage, which makes it possible to investigate the Q-dependence of these modes - at least it would if sufficient time were available on the instrument! Similarly, the fact that the time per sample on MARI is 4-6 days means that it is not feasible to carry out extensive studies as a function of composition, which is extremely important in the case of binary and multicomponent glasses. These experiments will become feasible at the SNS.


  13. Geophysical materials: silicate liquids and glasses (M. Wilding, UC Davis) - Silicate liquid behavior influences a variety of geochemical and geophysical processes. Although such liquids have a complex evolution over a range of pressure temperature and composition, considerable insight into their behavior can be obtained through study of simple silicate liquids and glasses that contain elements of geochemical interest. Of particular importance are silicate systems, which contain rare earth and transition metal elements. Thermodynamic measurements can be used to establish the macroscopic influence of such components but their mechanism of dissolution remains uncertain. Previous neutron scattering studies have provided important information on the structural role of Ca, Ti, Ni and Li in silicate glasses. These studies have used elements with isotopes of sufficiently different scattering lengths to enable study by isotopic substitution. The advent of the SNS with increased intensity, increased range of Q, increased resolution and potential for additional compositions available for isotopic substitution, provides an opportunity to expand this data base. The focus of such new studies would be to evaluate the structure of multicomponent glasses as a function of composition; to carry out phase diagram-based studies and to study the differences between liquid and glassy states. If combined with complementary spectroscopic techniques such as NMR, neutron scattering studies can provide a rigorous structural base for independent thermodynamic probes of such molecular liquids. Such developments will contribute to the understanding of a variety of processes of interest to the Earth Science Community, including the temperature-dependent rearrangement of melt structure, the solubility of H2O in silicate liquids, crystallization and melting processes, reactions at mineral surface, pre-melting of minerals and hydrothermal alteration.


  14. Microscopic Structure of 4He-3He Mixtures (P.Sokol, Penn State U) - The microscopic properties of pure 3He-4He mixtures are of considerable interest. Understanding these microscopic properties, such as the Bose condensate fraction, present a considerable challenge since they now involve quantum exchange effects among particles obeying different statistics. This statistical disorder leads to a variety of new behaviors, such as depression of the superfluid transition and suppression of the superfluid fraction. Recent experimental measurements using high energy inelastic neutron scattering have yielded surprising results, such as an increase of the Bose condensate fraction no, which is the microscopic order parameter for the superfluid phase, on the addition of 3He. Measurements of the kinetic energy per atom (KE) have suggested that the local environment of the atoms in the mixture is quite different from what any of the current theories predicts. Neutron structure measurements, in combination with x-ray measurements, can provide direct information on the various pair distribution functions for the mixture and elucidate the local structure of the liquid. High intensity, due to the high absorption cross section of 3He, and excellent statistical accuracy, due to the small differences in the local environment of the isotopes, will be required.


  15. Collective Excitations in Confined Superfluid Helium (P. Sokol, Penn State U) - Confinement of helium in disordered environments introduces profound changes in the behavior of the superfluid phase. When helium is liquefied in Vycor glass (with highly interconnected pores of less than 100 Å diameter), for example, the lambda transition is suppressed by about 0.2K, but the superfluid density exponent n is essentially unchanged from its bulk value (~0.67). For aerogel glass, which has a very open structure with a wide range of pore diameters, Tl is only suppressed by <0.01K whereas n is markedly increased (to ~0.81) indicating that the disordered helium now belongs in a different universality class. The disorder introduced by confinement affects many other macroscopic properties such as heat capacity, vorticity, and flow. An understanding of the microscopic dynamics, obtained through inelastic neutron scattering, is fundamental to developing a complete picture of these unique liquids. One of the most direct ways these microscopic dynamics are manifested is in the collective excitations, which are the fundamental excitations of the system and are directly related to the macroscopic properties of the liquid, such as the heat capacity and superfluid fraction. In superfluid helium, for example, these collective excitations are the well-known phonon-roton dispersion relation. The nature and interactions of these elementary excitations play a major role in determining the macroscopic properties of both the normal and superfluid phases. Measurements of the differences introduced by confinement will require excellent energy (~5-10 ueV) and momentum (~ 0.01-0.05 A-1) resolution.


  16. PDF Analysis Applied to Disordered Crystals (T. Egami, University of Pennsylvania) -- Many of today's advanced materials have complex structures with some degree of disorder at the atomic as well as the mesoscopic scale. Examples include the magnetic oxides with giant magnetoresistance, superconducting cuprates, ferroelectric and relaxor ferroelectric oxides, catalytic and catalytic support oxides, semicrystalline polymers, nanocrystalline particles, and semiconductor alloys. The traditional crystallographic approach has a very limited power in determining the structure of these materials. A powerful alternative is to apply the atomic pair-density function (PDF) analysis. Indeed our studies on many of the materials listed above resulted in many discoveries and novel understanding of the structure-properties relation. The pulsed neutron diffraction has been the best method to obtain the PDF, since the epithermal portion of the neutron spectrum provides ample neutrons with short wavelengths. By using the pulsed neutron sources we can determine the structure function up to 40 - 50 A-1, eliminating much of the termination errors from the Fourier-transform to obtain the PDF. The requirement of the instrument for such a purpose is the high intensity and the high resolution (< 0.2 %). Without high resolution the features at high Q will be lost, resulting in the loss of real space resolution in the PDF. The accuracy of the PDF analysis has been improved to the extent that it is equivalent in accuracy to the Rietveld powder diffraction analysis in determining the atomic positions in complex crystals. The new science that can be conducted at the SNS includes:
    1. The study of the local and mesoscopic structure of CMR oxides. We now understand the local structure of the CMR oxides, but how the local modifications (polarons) organize themselves in the meso-scopic scale is still open. Higher intensity and higher resolution will be needed to advance the PDF to the next stage to allow the meso-scopic structure study.
    2. Local structure of electronic ceramics, including the oxide with metal- insulator transition. The mechanism of the metal-insulator transition appears to involve the local lattice modifications in many cases. Determination of the local as well as mesoscopic structure through the metal-insulator transition will greatly advance our understanding.
    3. Local structure of nano-crystalline ceramics produced by bio-directed sol-gel processing. Here the mesoscopic nucleation of crystalline phases in the gel is the key in this process. Since the nuclei are small (although high in density in this method), conventional method will not be able to determine their structure.
    4. Local and meso-scopic structure of biological systems including proteins. The crystallization process used in protein crystallography often modifies the protein folding and its functionality. The PDF method allows the direct determination of the real space distances in the liquid solution so that the real structure of proteins can be understood.


  17. Structured Ion Conductors (J. W. Zwanziger, Indiana University) - The ability to structure materials on the nanoscopic scale through self-assembly techniques is opening new opportunities in materials science. One exciting approach is to use block-co-polymers as the structure directing agent, taking advantage of the mesophase separation into ordered arrays that is the thermodynamic equilibrium of these materials. We have developed a system for lithium ion conductivity, in which polyethylene oxide is used as one arm in a block-co-polymer. The PEO thus can be used to do double duty as both structure director and pathway for conduction. Our goal with this material is to use it as a solid electrolyte in batteries, in particular micro-batteries which could employ self-assembled ion-conducting lithium wires. To develop and exploit this system we need to understand both the structure and dynamics in the material, and neutron diffraction will be an essential part of his goal. Specifically, because of the multiple length scales and disorder within the polymer blocks, we require instrumentation suitable for disordered material diffraction which also has a significant overlap at low scattering vector with traditional small angle neutron diffractometers. At the SNS we have the opportunity to build such an instrument, which would be unique in the field and would make the SNS the premier facility world-wide for investigation with neutrons of mesocopically structured materials.


  18. Critical Micelle Conditions in Supercritical CO2 (H. D. Cochran, G. D. Wignall, ORNL, J. D. Londono, DuPont) -- We currently study the formation of micelles in supercritical CO2 using the SANS instrument at HFIR. These fundamental studies have great potential for practical application because the chemical industry is actively seeking ways to use supercritical CO2 to replace organic solvents, and already a number of processes for polymerization within micelles in CO2 are under development. It has been found that in supercritical CO2 there is a critical micelle density (analogous and in addition to the familiar critical micelle concentration in incompressible liquid media) below which micelles form and above which surfactant molecules are dispersed in solution. However, the surfactant concentrations and nascent micelle sizes of interest in studying the self-assembly of micelles demand wide angle neutron scattering experiments to complement SANS and higher flux than HFIR can provide. This is one of several efforts aimed at bridging the gulf between understanding of complex fluids at the atomic scale and their important properties at mesoscale through coupled scattering and molecular simulation studies.


  19. Chain Molecules in Supercritical CO2 (H. D. Cochran, G. D. Wignall, Y. B. Melnichenko, ORNL) - With SANS experiments we have studied variation of the radius of gyration of polymer chains in supercritical CO2. These experiments allow us to study the theta condition of polymer solutions as a function of density as well as temperature (usually the density effect is small in incompressible liquids). Both molecular simulations and statistical mechanically-based equations of state for polymer solutions can be most effectively tested with systems in which both density and temperature can be widely varied. The systems amenable so far to experimental study have been too large and complex for complementary atomistic molecular simulations. Thus, there is an incentive to pursue complementary wide angle neutron scattering experiments with simpler, smaller molecular structures (requiring lower concentrations and maximum neutron flux). This is one of several efforts aimed at bridging the gulf between understanding of complex fluids at the atomic scale and their important properties at mesoscale through coupled scattering and simulation studies.


  20. Chain Molecule Systems Under Shear (H. D. Cochran, H. J. Dai, ORNL, M. D. Dadmun, U. Tenn.) - We are building an ultra-high strain rate shear cell for scattering studies of the structure of chain molecule systems. The aim is to achieve overlap of strain rate between experiments and accurate, atomistic non-equilibrium molecular dynamics calculations. Currently, the highest strain rate achieved in carefully controlled experiments is <107s-1, and the lowest strain rate achieved in an accurate, atomistic simulation is >108s-1. Before simulation can reliably be used to test new molecular- level theories of fluids under shear flow, the quantitative accuracy of the simulations must be verified for real fluids. The first experiments will employ laser light scattering, but ultimately x-ray scattering and (hopefully) neutron scattering may be attempted. The requirement of extremely high strain rate in shear implies extremely short path length through the sheared sample, which will require the highest available neutron flux. Based on laser and x-ray results, the feasibility of neutron experiments at the SNS will be evaluated. This is one of several efforts aimed at bridging the gulf between understanding of complex fluids at the atomic scale and their important properties at mesoscale through coupled scattering and simulation studies.


  21. Structure Property Relations in Transition Metal Oxides (S. J. L. Billinge) -- Transition metal oxides have a wealth of interesting and potentially useful properties such as high- temperature superconductivity, ferroelectricity and colossal magnetoresistance. These come about because of interesting interplays between electronic and structural effects. Often structural distortions which strongly affect the properties are present which are disordered and cannot be studied crystallographically. We will be advancing high- resolution real-space techniques such as the atomic pair distribution function (PDF), and single crystal diffuse scattering techniques at the SNS to study these effects. High Q- resolution and a wide Q-range are necessary for these measurements as well as low backgrounds and stable moderator/detector systems and excellent statistics. This requires a spallation source with high flux and a dedicated instruments designed with these parameters in mind.


  22. Thermodynamics from diffraction (S. J. L. Billinge, P. G. Radaelli) -- A great deal of information about a material can be obtained from a small number of measurements and the application of the principles of thermodynamics. For example, the measurement of specific heat gives important (though incomplete) information about the density of states of a sample and therefore the bonding. This information is also stored in the thermal vibrational amplitudes of solids which can be measured using diffraction. We are reaching the point with instrumentation and analysis techniques that absolute displacement factors can be determined, as well as their temperature dependence, from powder diffraction. This can be done using Rietveld refinement, or refinement of the real- space pair distribution function. Rietveld is straightforward and yields the uncorrelated thermal factor which is a weighted sum over all the modes in the material. The PDF yields bond-specific thermal vibrations which give information about specific optical vibration modes. These values can be analyzed to obtain information about the bonding in materials without having to carry out difficult and time-consuming phonon dispersion measurements on single crystals, for example. For accurate absolute thermal factors, proper corrections for effects such as absorption and multiple scattering have to be made making an instrument with stable characteristics and low backgrounds important.


  23. Aqueous Electrolyte Solutions: Structural Studies (G. W. Neilson, Bristol) - Aqueous electrolyte solutions exhibit a rich variety of properties over a wide range of thermodynamic phase, and are significant components in many geological and biochemical fluid systems. Neutron diffraction when combined with isotopic substitution (NDIS) provides the only means currently available to determine the detailed interatomic structure around ions and water molecules in solution. A suitably configured and optimized diffractometer on the SNS will enable more extensive investigations to be carried out at lower ionic concentrations and into regimes of more biological significance. It will also allow for the determination of the structure around ions of elements with differences in neutron scattering lengths which are relatively small and not yet susceptible to the NDIS method (e.g. ions of Sn, U, Hf, Pb, etc). In the longer term, experiments may be successfully undertaken to monitor relatively slow but well-defined kinetic processes, or in the study of ionic coordination in the neighborhood of an electrode/electrolyte interface.


  24. Local Structure Studies of Pi-conjugated and Other Unconventional Polymers (M. J. Winokur, University of Wisconsin-Madison; B.R. Mattes, Los Alamos National Laboratory) - Conducting, pi-conjugated polymers continue to undergo a remarkable evolution in terms of their synthesis, processing, and materials properties. As a direct result of this focused effort there are now a wealth of new applications (highly selective separation membranes, biosensors, corrosion resistant coatings, light emitting diodes, microacutators) in addition to the many ``conventional'' uses originally envisioned. Despite the emphasis that is often placed on the quasi-one-dimensional nature of the host materials and the accompanying electronic excitations, it is the microscopic molecular organization and the precise control of this structure, with respect to both the intra-chain and inter-chain order, that often defines and ultimately limits these materials. Even relatively small changes in the specific chemical architecture and/or processing can lead to significant variations in the resultant structural forms and in their physical properties. With the fabrication of increasingly more complex architectures, there is an acute need to identify what are the local structural characteristics and which attributes play a key role in influencing the various structure/property relationships. One particularly notable family of materials is polyaniline and its related derivatives. Polyaniline films can be prepared as either amorphous or semicrystalline materials simply by changing the extent of hydrogen boding inhibitor when dispersed in a solution. Nominally identical crystalline materials can be prepared which range from insulating to metallic. Resolving systematic variations in the local intra-chain structure and intermolecular packing through pair-distribution analysis of the structure function is essential if this diverse structural behavior is to be fully understood. At present there is no US based neutron facility available for effectively undertaking many these studies. Some preliminary work has been begun using the SANDALS spectrometer (at ISIS) but the improved capabilities presented by the SNS, through construction of the liquid and disordered solids spectrometer, would dramatically extend the range of studies that could be accomplished.


  25. Glass Transitions (F. J. Bermejo, CSIC- Madrid) -- Although extensively studied during the last decades, the dynamics of the liquid -> glass transition remains as a poorly understood and a highly controversial. Part of the difficulties are of instrumental nature: the need to perform measurements over frequencies comprising many decades and the unsurmountable problem of combining data measured using wildly different time-windows. Future neutron sources can surely contribute towards the advance of our knowledge by : a) the development of backscattering (BS) spectrometers with nano-eV resolution, achievable using Bragg angles close to 90 deg and crystals such as GaAs; b) the development of BS spectrometers with active monochromators which will improve the appalling Q-resolution of the present-day spectrometers and c) the development of offset monochromators (J.C. Cook et al. Nucl.Inst. Meth. A312, 553 ,1992) which will enable the exploration of energy transfers up to at least 1 meV still retaining micro-eV resolution.



Appendix B. Organizing Committee (Back)

Price, David L., Argonne National Laboratory, 9700 S.Cass Avenue, Argonne IL 60439, price@anlpns.pns.anl.gov, phone: 630-252-5475, fax: 630-252-7777

Annis, Brian K., Oak Ridge National Laboratory, P. 0. Box 2008, Oak Ridge TN 37831-6197, annisbk@ornl.gov, phone: 423-574-5047, fax: 423-576-5235

Saboungi, Marie-Louise, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne lL 60439, saboungi@anlpns.pns.anl.gov, phone: 630-252-4341, fax: 630-252-7777

Habenschuss, Tony, Oak Ridge National Laboratory, P. 0. Box 2008, Oak Ridge TN 37831-6197, tth@ornl.gov, phone. 423-574-6018, fax: 423-576-5235



Appendix C. Workshop Agenda (Back)

SNS Workshop on Disordered Materials, 16-17 Oct 1998

Sponsored by Argonne and Oak Ridge National Laboratories

Building 360, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439

Friday, October 16, 1998

8:30 Coffee and Continental breakfast

9:00 WORKSHOP GOALS Bruce Brown (Director, IPNS)

Orientation: REVIEW OF SNS DESIGN Chair: Bruce Brown

9:10 Source, target(s), moderators Jack Carpenter (ANL)

9:40 Instrumentation and data acquisition Kent Crawford (ANL)

10:10 Coffee Break

Session A: LIQUID STRUCTURE: PERFORMANCE REQUIREMENTS Chair: Brian Annis (ORNL)

10:30 Hydrogenous liquids Marie-Claire Bellissent (Saclay)

10:50 High-temperature liquids Marie-Louise Saboungi (ANL)

11:10 Aqueous solutions George Neilson (Bristol University)

11:30 Liquid polymers Brian Annis (ORNL)

11:50 Review of HIPPO (diffractometer proposed for LANSCE) Bob Von Dreele (LANL)

12:10 Lunch

1:10 Discussion of performance requirements for liquid structure Moderator: Alan Soper (ISIS)

Session B: GLASS & DISORDERED SOLID STRUCTURE: PERFORMANCE REQUIREMENTS Chair: Takeshi Egami (Univ. of Penn.)

2:10 Intermediate- and short-range order in glasses Adrian Wright (Reading University)

2:30 Ternary glasses Joe Zwanziger (Indiana University)

2:50 Fast-ion conducting glasses Lars Borjesson (Chalmers Institute of Technology, Goteborg)

3:10 Coffee Break

3:30 Geophysical materials Martin Wilding (UC, Davis)

3:50 Local correlations in solids Takeshi Egami (Univ. of Penn.)

4:10 Disordered polymers Michael Winokur (Univ. of Wisc.)

4:30 Small-angle scattering from porous materials Sow-Hsin Chen (MIT)

6:00 Workshop dinner (Argonne Guest House)

Saturday, October 17, 1998

9:00 Coffee and Continental breakfast

9:30 Discussion of performance requirements for glass & disordered solid structure Moderator: Spencer Howells (ISIS)

Session C: DYNAMICS OF DISORDERED MATERIALS: PERFORMANCE REQUIREMENTS Chair: David Price (ANL)

10:30 Coffee Break

10:50 Soft matter Sow-Hsin Chen (MIT)

11:10 Quantum systems Paul Sokol (Penn. St. Univ.)

11:30 Vibrational spectroscopy Chun Loong (ANL)

11:50 Relaxation processes Franz Trouw (ANL)

12:10 Lunch

1:00 Discussion of performance requirements for dynamics of disordered materials Moderator: Sow-Hsin Chen (MIT)

2:00 Breakout groups A, B, C (corresponding to sessions above) to draft reports

4:00 Plenary meeting to discuss preparation of report and presentation at SNS Users Meeting, Knoxville,

November 9-11, 1998. Chair: Brian Annis

5:00 Adjourn



Appendix D. List of Workshop Participants (Back)

Annis, Brian, Oak Ridge National Laboratory, P. 0. Box 2008, Oak Ridge TN 37831-6197, annisbk@ornl.gov phone: 423-574-5047, fax: 423-576-5235

Bellissent, Marie-Claire, Laboratoire Leon Brillouin, 3 Rue Michel Ange, 75974 Paris, France, mcbel@LLB.saclay.cea.fr phone: 33+1-69-08-60-66, fax: 33+1-69-33--14-87

Borjesson, Lars, Chalmers University of Technology, S-412 96 Gothenburg, Sweden, borje@fy.chalmers.se phone: +46-31-772-33-07, fax: +46-31-772-20-90

Brown, Bruce, Argonne National Laboratory , 9700 S. Cass Avenue , Argonne IL 60439, bsbrown@anl.gov phone: 630-252-4999, fax: 630-252-4163

Carpenter, Jack, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne lL 60439, jmcarpenter@anl.gov phone: 630-252-5519, fax: 630-252-4163

Chen, Sow-Hsin, Massachusetts Institute of Technology, 24-209, Dept. of Nuclear Eng., Cambridge MA 02139, sowhsin@mit.edu phone- 617-253-3810, fax: 617-258-8863

Cochran, Hank D., Oak Ridge National Laboratory, P. 0. Box 2009, Oak Ridge TN 37831-6224, hdc@ornl.gov phone: 423-574-6821, fax: 423-241-4829

Crawford, Kent, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne IL 60439, rkcrawford@anl.gov phone: 630-252-7769, fax: 630-252-4163

Egami, Takeshi, University of Pennsylvania, 3231 Walnut Street, Philadelphia PA 19104, egami@seas.upenn.edu phone: 215-898-5138, fax: 215-573-2128

Habenschuss, Tony, Oak Ridge National Laboratory, P. 0. Box 2008, Oak Ridge TN 37831-6197, tth@ornl.gov phone. 423-574-6018, fax: 423-576-5235

Howells, William Spencer, ISIS Facility. Rutherford Appleton Lab., Chilton, Didcot, OX11 OQX, UK, wsh@isise.rl.ac.uk phone: +44-1235-44-5680, fax- +44-1235-44-5720

Londono, David, E.I. DuPont de Nemours, P.O. Box 80323 Bldg. B323, Wilmington DE 19880-0323, j-david.londono@usa.dupont.com phone: 302-695-1222, fax: 302-695-1513

Loong, Chun, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne IL 69439, phone: 630-252-5596, fax: 630-252-4163

Neilson, George, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL, UK, george.w.neilson@bristol.ac.uk phone: 44-117-9288706, fax: 44-117-9255624

Price, David L., Argonne National Laboratory, 9700 S.Cass Avenue, Argonne IL 60439, dlprice@anl.gov phone: 630-252-5475, fax: 630-252-7777

Robertson, Lee, Oak Ridge National Laboratory, Bldg. 7962, MS 6393, Oak Ridge TN 37831-6393, robertsonjl@ornl.gov phone: 423-574-5243, fax: 423-574-6268

Saboungi, Marie-Louise, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne lL 60439, saboungi@anlpns.pns.anl.gov phone: 630-252-4341, fax: 630-252-7777

Simonson, J. Mike, Oak Ridge National Laboratory, P. O. Box 2008, Bldg. 4500S, Oak Ridge TN 37831-6110, simonsonJM@ornl.gov phone: 423-574-4962, fax: 423-574 4961

Sokol, Paul, Pennsylvania State University,, Dept. of Phys. 104 Davey Lab., University Park PA 16802, pes4@psu.edu phone: 814-863-5811, fax: 814-865-3604

Soper, Alan, ISIS, Rutherford Appleton Laboratory, Chilton, Didcot OXON , OX11 OQX, UK, aks@isise.rl.ac.uk phone: +44-1235-445543, fax: +44-1235-445642

Trouw, Frans, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne IL 60439, ftrouw@anl.gov phone: 630-252-7665, fax: 630-252-4163

Von Dreele, Robert, Los Alamos National Laboratory, Los Alamos NM, vondreele@popler.lansce.lanl.gov phone:, fax:

Wilding, Martin, University of California/Davis, Davis CA 95616, mcwilding@ucdavis.edu phone: 530-754-2133, fax: 530-752-9307

Winokur, Michael, University of Wisconsin, Dept. of Physics, Madison WI 53706, winokur@romano.physics.wisc.edu phone: 608-262-7475, fax: 609-265-2334

Wright, Adrian, J. J. Thompson Physical Laboratory, University of Reading, Whiteknights Reading, RG6 6AF UK, A.C.Wright@reading.ac.uk phone: +44-119-931-8555, fhx: +44-118-975-0203

Zwanziger, Josef, Indiana University, Dept. of Chemistry, Bloomington Indiana 47405, jzwanzig@indiana.edu phone: 812-855-3994, fax: 812-855-8300



Acknowledgments (Back)

The enthusiastic contributions of the workshop participants to this report are gratefully recognized, especially the advice and preliminary summaries by the session chairs Alan K Soper, ISIS, Spencer Howells, ISIS, and Sow-Hsin Chen (MIT).

The generous support for the workshop and this report from the IPNS staff are gratefully acknowledged. Program development funds from ORNL and ANL to defray the costs of the workshop are also acknowledged.