Structure determination of an amorphous compound AlB4H11.

Abstract

The structure of the amorphous aluminoborane compound AlB4H11 was identified through a collaborative study closely coupling a first-principles density functional based approach with experimental measurements using IR, NMR, and neutron vibrational spectroscopy (NVS). The AlB4H11 structure was found to contain distinct [BH4] and [B3H7] units without any [AlH4] units. It forms a –[B3H7]–Al(BH4)– polymer chain with the [BH4] units twisted relative to each other perpendicular to the chain direction and bonded to Al, and a chain backbone consists of [B3H7] and Al where the [B3H7] unit exhibits a triangular boron configuration. The computed lowest energy structure shows good agreement with results of IR, NVS and NMR spectra; this agreement demonstrates the extended applicability of the structure prediction approach to the prediction of even amorphous compounds.