Crystal structure of Ca(AlH4)2 predicted from density-functional band-structure calculations -: art. no. 144111

Calcium alanate [Ca(AlH4)(2)] is a candidate material for high-density reversible solid-state hydrogen storage that thus far has been scarcely studied. This paper presents a scheme for solving the crystal structure of a compound based on only a few model structures from similar compounds and employs this to predict the crystal structure and electronic structure of Ca(AlH4)(2). By deliberately breaking the symmetry of the model structures down to P1, local minima may be avoided, and thus the number of required input models is smaller. Density-functional band-structure calculations within the generalized gradient approximation were used in the structural minimizations. The most stable structure was based on Ca(BaF4)(2) and was in the orthorhombic space group Pbca with lattice constants a=1337, b=928, and c=891 pm. The electronic density of states reveals an insulator with a band gap of around 4 eV.