Materials Data on KNa(BH4)2 by Materials Project

Abstract

NaK(BH4)2 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. K1+ is bonded to twelve equivalent H+0.50+ atoms to form KH12 cuboctahedra that share edges with six equivalent KH12 cuboctahedra, edges with six equivalent NaH12 cuboctahedra, and edges with six equivalent BH4 tetrahedra. All K–H bond lengths are 2.79 Å. Na1+ is bonded to twelve H+0.50+ atoms to form distorted NaH12 cuboctahedra that share edges with six equivalent KH12 cuboctahedra, edges with six equivalent NaH12 cuboctahedra, and edges with six equivalent BH4 tetrahedra. There are six shorter (2.44 Å) and six longer (2.67 Å) Na–H bond lengths. B3- is bonded to four H+0.50+ atoms to form BH4 tetrahedra that share edges with three equivalent KH12 cuboctahedra and edges with three equivalent NaH12 cuboctahedra. There is one shorter (1.22 Å) and three longer (1.23 Å) B–H bond length. 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 Na1+ and one B3- atom. In the second H+0.50+ site, H+0.50+ is bonded in a distorted single-bond geometry to two equivalent K1+, one Na1+, and one B3- atom.