Materials Data on K2NaAlH6 by Materials Project

Abstract

K2NaAlH6 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. K1+ is bonded to twelve H1- atoms to form KH12 cuboctahedra that share corners with twelve equivalent KH12 cuboctahedra, faces with six equivalent KH12 cuboctahedra, faces with four equivalent NaH6 octahedra, and faces with four equivalent AlH6 octahedra. There are a spread of K–H bond distances ranging from 2.86–2.91 Å. Na1+ is bonded to six H1- atoms to form NaH6 octahedra that share corners with six equivalent AlH6 octahedra and faces with eight equivalent KH12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are two shorter (2.28 Å) and four longer (2.29 Å) Na–H bond lengths. Al3+ is bonded to six H1- atoms to form AlH6 octahedra that share corners with six equivalent NaH6 octahedra and faces with eight equivalent KH12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–2°. All Al–H bond lengths are 1.78 Å. There are two inequivalent H1- sites. In the first H1- site, H1- is bonded in a distorted linear geometry to four equivalent K1+, one Na1+, and one Al3+ atom. In the second H1- site, H1- is bonded in a distorted linear geometry to four equivalent K1+, one Na1+, and one Al3+ atom.