A topological study of bonding in the Al2H2 and Al2H4 hydrides

A topological analysis of the hydrogen-bridged and non-bridged Al2H2 and Al2H4 hydrides has been carried out using energies and geometries found at the CCSD(T)/cc-pvtz level and B3LYP/cc-pvtz Kohn-Sham wavefunctions at the optimized geometries for ELF and AIM analyses. Our topological analysis confirms earlier bonding pictures and leads to a better understanding of these unusual systems. Virtually all cases involving bridged species can be pictured in terms of donor-acceptor interactions involving hydrogen and lone pairs. Two cases of relatively weak bent Al-Al bonds are found and the unusual trans-bent HAlAlH molecule is seen to have a bond order just somewhat larger than unity.