Materials Data on K7NbAs4 by Materials Project
K7NbAs4 crystallizes in the orthorhombic Pmn2_1 space group. The structure is three-dimensional. there are five inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to four As3- atoms to form distorted KAs4 tetrahedra that share corners with two equivalent NbAs4 tetrahedra, corners with four equivalent KAs4 tetrahedra, and an edgeedge with one NbAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.25–3.47 Å. In the second K1+ site, K1+ is bonded in a 5-coordinate geometry to five As3- atoms. There are a spread of K–As bond distances ranging from 3.44–3.79 Å. In the third K1+ site, K1+ is bonded in a 4-coordinate geometry to one K1+ and four As3- atoms. The K–K bond length is 3.36 Å. There are a spread of K–As bond distances ranging from 3.20–3.56 Å. In the fourth K1+ site, K1+ is bonded in a 5-coordinate geometry to one K1+ and four As3- atoms. There are a spread of K–As bond distances ranging from 3.49–3.87 Å. In the fifth K1+ site, K1+ is bonded in a distorted trigonal non-coplanar geometry to three As3- atoms. There are one shorter (3.26 Å) and two longer (3.36 Å) K–As bond lengths. Nb5+ is bonded to four As3- atoms to form NbAs4 tetrahedra that share corners with four equivalent KAs4 tetrahedra and edges with two equivalent KAs4 tetrahedra. There are a spread of Nb–As bond distances ranging from 2.51–2.56 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 5-coordinate geometry to seven K1+ and one Nb5+ atom. In the second As3- site, As3- is bonded in a 1-coordinate geometry to seven K1+ and one Nb5+ atom. In the third As3- site, As3- is bonded in a 1-coordinate geometry to eight K1+ and one Nb5+ atom.