Crystal structures and electronic structures of alkali aluminohexahydrides from density functional calculations

Abstract

The crystal structure of four bialkali alanates has been calculated by accurate density functional band structure calculations: K 2LiAlH 6, K 2NaAlH 6, KNa 2AlH 6, and LiNa 2AlH 6. The latter hydride has been synthesized previously, but its crystal structure has not been reported before. The former three have previously been shown to be stable. They are all quite similar to the calculated Na 3AlH 6 and K 3AlH 6 structures, which are also presented. The unit cell size and the tilting angle of the AlH 6 octahedra are the largest differences between the structures. Total and local densities of states are presented as well as a Hirshfeld charge analysis for all the stable compounds.