Materials Data on K2Cd3SnAs4 by Materials Project
K2Cd3SnAs4 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six As3- atoms to form KAs6 octahedra that share corners with five equivalent SnAs4 tetrahedra, corners with seven CdAs4 tetrahedra, edges with six KAs6 octahedra, an edgeedge with one SnAs4 tetrahedra, and edges with five CdAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.31–3.54 Å. In the second K1+ site, K1+ is bonded to six As3- atoms to form KAs6 octahedra that share a cornercorner with one SnAs4 tetrahedra, corners with eleven CdAs4 tetrahedra, edges with six KAs6 octahedra, edges with two equivalent SnAs4 tetrahedra, and edges with four CdAs4 tetrahedra. There are a spread of K–As bond distances ranging from 3.38–3.59 Å. There are three inequivalent Cd2+ sites. In the first Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with six KAs6 octahedra, corners with two equivalent CdAs4 tetrahedra, corners with four equivalent SnAs4 tetrahedra, edges with three KAs6 octahedra, and edges with three CdAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 19–52°. There are a spread of Cd–As bond distances ranging from 2.76–2.88 Å. In the second Cd2+ site, Cd2+ is bonded to four As3- atoms to form distorted CdAs4 tetrahedra that share corners with six KAs6 octahedra, corners with six CdAs4 tetrahedra, edges with three KAs6 octahedra, an edgeedge with one CdAs4 tetrahedra, and edges with two equivalent SnAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–48°. There are a spread of Cd–As bond distances ranging from 2.63–3.10 Å. In the third Cd2+ site, Cd2+ is bonded to four As3- atoms to form CdAs4 tetrahedra that share corners with six KAs6 octahedra, corners with six CdAs4 tetrahedra, edges with three KAs6 octahedra, an edgeedge with one SnAs4 tetrahedra, and edges with two equivalent CdAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–50°. There are a spread of Cd–As bond distances ranging from 2.67–3.08 Å. Sn4+ is bonded to four As3- atoms to form SnAs4 tetrahedra that share corners with six KAs6 octahedra, corners with two equivalent SnAs4 tetrahedra, corners with four equivalent CdAs4 tetrahedra, edges with three KAs6 octahedra, and edges with three CdAs4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–47°. There are two shorter (2.69 Å) and two longer (2.77 Å) Sn–As bond lengths. There are four inequivalent As3- sites. In the first As3- site, As3- is bonded to three K1+ and four Cd2+ atoms to form distorted edge-sharing AsK3Cd4 pentagonal bipyramids. In the second As3- site, As3- is bonded in a 7-coordinate geometry to three K1+, three Cd2+, and one Sn4+ atom. In the third As3- site, As3- is bonded in a 7-coordinate geometry to three K1+, three Cd2+, and one Sn4+ atom. In the fourth As3- site, As3- is bonded in a 7-coordinate geometry to three K1+, two Cd2+, and two equivalent Sn4+ atoms.