Structure determination of an amorphous compound AlB4H11Electronic supplementary information (ESI) available: For details of the crystal structure information for structures Str-0, Str-86, Str-108, Str-260, Str-400, and Str-640, 11B NMR spectra information. See DOI: 10.1039/c2sc21100a

The structure of the amorphous aluminoborane compound AlB 4 H 11 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 AlB 4 H 11 structure was found to contain distinct [BH 4 ] and [B 3 H 7 ] units without any [AlH 4 ] units. It forms a -[B 3 H 7 ]-Al(BH 4 )- polymer chain with the [BH 4 ] units twisted relative to each other perpendicular to the chain direction and bonded to Al, and a chain backbone consists of [B 3 H 7 ] and Al where the [B 3 H 7 ] 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. Successful identification of the AlB 4 H 11 structure demonstrates that the PEGS + DFT method can even predict the structure of an amorphous compound.