Structure and stability of possible new alanates

Three new stable bialkalimetallic alanates are predicted by accurate density functional calculations: \chem{K_2LiAlH_6}, \chem{K_2NaAlH_6}, and \chem{KNa_2AlH_6}. Their detailed crystal structure has been determined by a systematic search through a large part of the probable space of crystal structures. They are thermodynamically stable at 0\un{K} compared to their monoalkali constituents by 9 to 49\un{kJ/mol} formula units. The crystal structure of the already known alanates \chem{Li_3AlH_6}, \chem{Na_3AlH_6}, \chem{K_3AlH_6}, and \chem{LiNa_2AlH_6} were also determined, and found to be in excellent agreement with experimental data where available. The two last bialkali alanates studied, \chem{Li_2NaAlH_6} and \chem{KLi_2AlH_6}, were found to be unstable

Formation enthalpies of

Crystal structures and enthalpies of formation of complex hydrides of magnesium have been investigated through band structure calculations based on density functional theory. As for many other inorganic solids, experimental crystal structures are excellently reproduced by the computational results. Further, experimental reaction energies are very well reproduced for reactions involving reactants and products with similar electronic structures. This good correspondence enables us to indicate the correct heat of formation value in cases where highly disagreeing experimental results exist in the literature