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Research Highlight

Integrated Molecular Simulations and Neutron Scattering Reveal the Energetics of Hydrogen Bonds at a Mineral Surface

Comparison of the VDOS for water and OH groups extracted from INS measurements at incident energies of 250 and 600 meV (circles) with the VDOS extracted from AIMD simulations of the (110) surface of SnO2 (cassiterite).  BH = wagging mode of bridging hydroxyl motions in directions parallel (x,y) and perpendicular (z) to the surface, as well as terminal water (TW) and terminal OH (TH) motions.

Scientific Achievement

Inelastic neutron scattering (INS) studies of water sorbed on tin oxide (SnO2, cassiterite) nanoparticle surfaces at low humidity and ab initio molecular dynamics (AIMD) simulations were independently analyzed to extract the vibrational density of states (VDOS) of water and OH groups, showing the effects of water dissocation and very strong intra-surface H-bonds.

Significance and Impact

The vibrational peaks in the INS spectrum from H2O and OH vibrational dynamics in the 0-200 meV range, and OH stretching modes at higher energies can be uniquely assigned to specific surface species motions using AIMD simulations.

Research Details

  • INS spectra were collected on the SEQUOIA spectrometer at ORNL’s Spallation Neutron Source
  • AIMD simulations were conducted using ORNL’s JAGUAR supercomputer