Materials Data on K3AlH6 by Materials Project
K3AlH6 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to eight H1- atoms to form distorted KH8 hexagonal bipyramids that share corners with four equivalent KH8 hexagonal bipyramids, edges with six equivalent KH8 hexagonal bipyramids, and edges with four equivalent AlH6 octahedra. There are four shorter (2.60 Å) and four longer (2.95 Å) K–H bond lengths. In the second K1+ site, K1+ is bonded in a linear geometry to two equivalent H1- atoms. Both K–H bond lengths are 2.69 Å. Al3+ is bonded to six H1- atoms to form AlH6 octahedra that share edges with eight equivalent KH8 hexagonal bipyramids. There is four shorter (1.73 Å) and two longer (1.93 Å) Al–H bond length. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded in a distorted trigonal planar geometry to two equivalent K1+ and one Al3+ atom. In the second H1- site, H1- is bonded to five K1+ and one Al3+ atom to form a mixture of distorted edge and corner-sharing HK5Al octahedra. The corner-sharing octahedra tilt angles range from 0–15°.