Materials Data on K3Mg18Sn11 by Materials Project
K3Mg18Sn11 crystallizes in the hexagonal P6_3/m space group. The structure is three-dimensional. there are two inequivalent K sites. In the first K site, K is bonded in a 12-coordinate geometry to six Mg and six Sn atoms. All K–Mg bond lengths are 3.84 Å. There are three shorter (3.66 Å) and three longer (3.69 Å) K–Sn bond lengths. In the second K site, K is bonded to six equivalent Mg and six equivalent Sn atoms to form distorted KMg6Sn6 cuboctahedra that share corners with eighteen MgSn4 tetrahedra and edges with nine MgK2Sn4 tetrahedra. All K–Mg bond lengths are 3.84 Å. All K–Sn bond lengths are 3.69 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five Sn atoms. There are a spread of Mg–Sn bond distances ranging from 2.97–3.09 Å. In the second Mg site, Mg is bonded to four Sn atoms to form distorted MgSn4 tetrahedra that share corners with two equivalent KMg6Sn6 cuboctahedra, corners with eleven MgSn4 tetrahedra, and edges with three MgK2Sn4 tetrahedra. There are a spread of Mg–Sn bond distances ranging from 2.89–3.04 Å. In the third Mg site, Mg is bonded to two equivalent K and four Sn atoms to form distorted MgK2Sn4 tetrahedra that share corners with twelve MgSn4 tetrahedra, an edgeedge with one KMg6Sn6 cuboctahedra, edges with six MgSn4 tetrahedra, and faces with two equivalent MgK2Sn4 tetrahedra. There are a spread of Mg–Sn bond distances ranging from 2.91–2.99 Å. In the fourth Mg site, Mg is bonded to two K and four Sn atoms to form distorted MgK2Sn4 tetrahedra that share a cornercorner with one KMg6Sn6 cuboctahedra, corners with twelve MgSn4 tetrahedra, an edgeedge with one KMg6Sn6 cuboctahedra, edges with six MgSn4 tetrahedra, and faces with two equivalent MgK2Sn4 tetrahedra. There are a spread of Mg–Sn bond distances ranging from 2.94–3.01 Å. There are three inequivalent Sn sites. In the first Sn site, Sn is bonded in a 6-coordinate geometry to six Mg atoms. In the second Sn site, Sn is bonded in a 9-coordinate geometry to two K and seven Mg atoms. In the third Sn site, Sn is bonded in a 9-coordinate geometry to two equivalent K and seven Mg atoms.