Materials Data on KNa(BH4)2 by Materials Project

Abstract

NaK(BH4)2 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. K1+ is bonded to twelve H+0.50+ atoms to form KH12 cuboctahedra that share corners with six equivalent NaH6 octahedra, edges with six equivalent KH12 cuboctahedra, and edges with six equivalent BH4 tetrahedra. The corner-sharing octahedral tilt angles are 60°. There are six shorter (2.72 Å) and six longer (2.82 Å) K–H bond lengths. Na1+ is bonded to six equivalent H+0.50+ atoms to form NaH6 octahedra that share corners with six equivalent KH12 cuboctahedra and corners with six equivalent BH4 tetrahedra. All Na–H bond lengths are 2.42 Å. B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share corners with three equivalent NaH6 octahedra and edges with three equivalent KH12 cuboctahedra. The corner-sharing octahedral tilt angles are 66°. All B–H bond lengths are 1.23 Å. There are two inequivalent H+0.50+ sites. In the first H+0.50+ site, H+0.50+ is bonded in a single-bond geometry to three equivalent K1+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to one K1+, one Na1+, and one B3- atom.