Materials Data on K3Mg18Pb11 by Materials Project

Abstract

K3Mg18Pb11 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 Pb atoms. There are three shorter (3.70 Å) and three longer (3.74 Å) K–Pb bond lengths. In the second K site, K is bonded to six equivalent Mg and six equivalent Pb atoms to form distorted KMg6Pb6 cuboctahedra that share corners with eighteen MgPb4 tetrahedra and edges with nine MgPb4 tetrahedra. All K–Mg bond lengths are 3.92 Å. All K–Pb bond lengths are 3.72 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five Pb atoms. There are a spread of Mg–Pb bond distances ranging from 3.05–3.19 Å. In the second Mg site, Mg is bonded to four Pb atoms to form distorted MgPb4 tetrahedra that share corners with two equivalent KMg6Pb6 cuboctahedra, corners with eleven MgPb4 tetrahedra, and edges with three MgPb4 tetrahedra. There are a spread of Mg–Pb bond distances ranging from 2.93–3.11 Å. In the third Mg site, Mg is bonded to four Pb atoms to form MgPb4 tetrahedra that share corners with twelve MgPb4 tetrahedra, an edgeedge with one KMg6Pb6 cuboctahedra, and edges with four MgPb4 tetrahedra. There are one shorter (2.95 Å) and three longer (3.03 Å) Mg–Pb bond lengths. In the fourth Mg site, Mg is bonded to one K and four Pb atoms to form distorted MgKPb4 tetrahedra that share a cornercorner with one KMg6Pb6 cuboctahedra, corners with eleven MgPb4 tetrahedra, an edgeedge with one KMg6Pb6 cuboctahedra, and edges with seven MgPb4 tetrahedra. There are a spread of Mg–Pb bond distances ranging from 2.99–3.06 Å. There are three inequivalent Pb sites. In the first Pb site, Pb is bonded in a 6-coordinate geometry to six Mg atoms. In the second Pb site, Pb is bonded in a 9-coordinate geometry to two K and seven Mg atoms. In the third Pb site, Pb is bonded in a 9-coordinate geometry to two equivalent K and seven Mg atoms.