Materials Data on CaMg6Nb by Materials Project

Abstract

CaMg6Nb is beta Cu3Ti-derived structured and crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. Ca is bonded to twelve Mg atoms to form CaMg12 cuboctahedra that share corners with four equivalent CaMg12 cuboctahedra, corners with eight equivalent NbMg12 cuboctahedra, edges with eight equivalent MgCa2Mg8Nb2 cuboctahedra, faces with two equivalent CaMg12 cuboctahedra, faces with four equivalent MgCa2Mg8Nb2 cuboctahedra, and faces with four equivalent NbMg12 cuboctahedra. There are a spread of Ca–Mg bond distances ranging from 3.18–3.35 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded to two equivalent Ca, eight Mg, and two equivalent Nb atoms to form distorted MgCa2Mg8Nb2 cuboctahedra that share corners with twelve equivalent MgCa2Mg8Nb2 cuboctahedra, edges with four equivalent CaMg12 cuboctahedra, edges with four equivalent NbMg12 cuboctahedra, faces with two equivalent CaMg12 cuboctahedra, faces with two equivalent NbMg12 cuboctahedra, and faces with six equivalent MgCa2Mg8Nb2 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.19–3.23 Å. There are one shorter (3.17 Å) and one longer (3.20 Å) Mg–Nb bond lengths. In the second Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Ca, eight Mg, and two equivalent Nb atoms. There are a spread of Mg–Mg bond distances ranging from 2.92–3.45 Å. Both Mg–Nb bond lengths are 3.07 Å. In the third Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Ca, eight Mg, and two equivalent Nb atoms. Both Mg–Nb bond lengths are 3.08 Å. In the fourth Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent Ca, eight Mg, and two equivalent Nb atoms. Both Mg–Nb bond lengths are 3.09 Å. Nb is bonded to twelve Mg atoms to form NbMg12 cuboctahedra that share corners with four equivalent NbMg12 cuboctahedra, corners with eight equivalent CaMg12 cuboctahedra, edges with eight equivalent MgCa2Mg8Nb2 cuboctahedra, faces with two equivalent NbMg12 cuboctahedra, faces with four equivalent CaMg12 cuboctahedra, and faces with four equivalent MgCa2Mg8Nb2 cuboctahedra.