Structure determination of an amorphous compound AlB4H11

Abstract

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.

Search for the global minimum structures of AlB3H2n(n = 0 − 6) clusters

“…[2][3][4][5][6][7][8] Group 13 hydrides are of importance in the chemistry of materials, organic synthesis, organometallic catalysis, hydrogen storage applications, [9,10] and jet fuel. [16,17]. Hence, aluminoborane compounds may be good candidates for hydrogen storage due to their very high hydrogen capacity, moderate stability in terms of a decomposition temperature, fast hydrogen recharging kinetics, and attractive hydrogen fragmentation temperature, see Refs.…”

“…[11] For instance, aluminoborane compounds may have very attractive properties for hydrogen storage, as boron has many different types of hydrides [12][13][14][15] and aluminium reduces the decomposition temperatures of hydrides. [17] There are various theoretical approaches to cluster searching. [16,17].…”

“…[16,17]. [9,11,[19][20][21][22][23] For instance, aluminum borohydride, Al(BH 4 ) 3 , was synthesized quite early on and investigated in detail by different groups, see Refs. [17] There are various theoretical approaches to cluster searching.…”

Structure, Ionization, and Fragmentation of Hydrogenated Aluminoboron Clusters: Al2B2H2n (n=0‐6)

“…The replacement of a boron atom by an aluminum atom in an aluminoborane cluster could induce a significant change in the electronic properties. Therefore, an understanding of the structural variations and stabilities of aluminoborane series is also of great interest …”

Synthesis, structural analysis, and thermal decomposition studies of [(NH3)2BH2]B3H8

“…For example, the synthesis of AlB 4 H 11 requires diborane (B 2 H 6 ), which is highly flammable and consequently necessitates high quality vacuum apparatus and strong experience. 11,14 To make a compound interesting for hydrogen storage, its synthetic ease and availability are apparently of great importance.…”