Materials Data on K3Nb2CuSe12 by Materials Project
K3Nb2CuSe12 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 8-coordinate geometry to eight Se+1.33- atoms. There are a spread of K–Se bond distances ranging from 3.39–3.73 Å. In the second K1+ site, K1+ is bonded in a 9-coordinate geometry to nine Se+1.33- atoms. There are a spread of K–Se bond distances ranging from 3.43–3.88 Å. In the third K1+ site, K1+ is bonded in a 9-coordinate geometry to nine Se+1.33- atoms. There are a spread of K–Se bond distances ranging from 3.35–4.01 Å. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to seven Se+1.33- atoms to form distorted NbSe7 pentagonal bipyramids that share an edgeedge with one CuSe4 tetrahedra and a faceface with one NbSe7 pentagonal bipyramid. There are a spread of Nb–Se bond distances ranging from 2.45–2.97 Å. In the second Nb5+ site, Nb5+ is bonded to seven Se+1.33- atoms to form distorted NbSe7 pentagonal bipyramids that share an edgeedge with one CuSe4 tetrahedra and a faceface with one NbSe7 pentagonal bipyramid. There are a spread of Nb–Se bond distances ranging from 2.46–2.89 Å. Cu3+ is bonded to four Se+1.33- atoms to form CuSe4 tetrahedra that share edges with two NbSe7 pentagonal bipyramids. There are a spread of Cu–Se bond distances ranging from 2.39–2.55 Å. There are twelve inequivalent Se+1.33- sites. In the first Se+1.33- site, Se+1.33- is bonded in a 1-coordinate geometry to three K1+, one Nb5+, and one Se+1.33- atom. The Se–Se bond length is 2.78 Å. In the second Se+1.33- site, Se+1.33- is bonded in a 6-coordinate geometry to two K1+, one Nb5+, one Cu3+, and two Se+1.33- atoms. The Se–Se bond length is 2.55 Å. In the third Se+1.33- site, Se+1.33- is bonded in a 2-coordinate geometry to four K1+, one Nb5+, and one Cu3+ atom. In the fourth Se+1.33- site, Se+1.33- is bonded in a 1-coordinate geometry to two K1+, one Nb5+, and two Se+1.33- atoms. There are one shorter (2.42 Å) and one longer (3.35 Å) Se–Se bond lengths. In the fifth Se+1.33- site, Se+1.33- is bonded in a 6-coordinate geometry to one K1+ and five Se+1.33- atoms. There are a spread of Se–Se bond distances ranging from 2.44–3.52 Å. In the sixth Se+1.33- site, Se+1.33- is bonded in a 5-coordinate geometry to four K1+, one Nb5+, and one Cu3+ atom. In the seventh Se+1.33- site, Se+1.33- is bonded in a 3-coordinate geometry to two K1+, one Nb5+, and one Se+1.33- atom. The Se–Se bond length is 2.43 Å. In the eighth Se+1.33- site, Se+1.33- is bonded in a 3-coordinate geometry to two K1+, two Nb5+, and one Se+1.33- atom. In the ninth Se+1.33- site, Se+1.33- is bonded in a 1-coordinate geometry to one K1+, two Nb5+, and one Se+1.33- atom. In the tenth Se+1.33- site, Se+1.33- is bonded in a 1-coordinate geometry to two equivalent K1+, one Nb5+, and two Se+1.33- atoms. The Se–Se bond length is 2.45 Å. In the eleventh Se+1.33- site, Se+1.33- is bonded in a 2-coordinate geometry to one K1+, two Nb5+, and one Se+1.33- atom. In the twelfth Se+1.33- site, Se+1.33- is bonded in a 4-coordinate geometry to two K1+, one Nb5+, one Cu3+, and one Se+1.33- atom.