Structure and stability of possible new alanates

Three new stable bialkalimetallic alanates are predicted by accurate density functional calculations: K2LiAlH6, K2NaAlH6, and KNa2AlH6. 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 K compared to their monoalkali constituents by 9 to 49 kJ/mol formula units. The crystal structure of the already known alanates Li3AlH6, Na3AlH6, K3AlH6, and LiNa2AlH6 were also determined, and found to be in excellent agreement with experimental data where available. The two last bialkali alanates studied. Li2NaAlH6 and KLi2AlH6, were found to be unstable.