Materials Data on CaMg by Materials Project

Abstract

MgCa crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. there are three inequivalent Ca sites. In the first Ca site, Ca is bonded to five Ca and seven Mg atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with nine equivalent CaCa5Mg7 cuboctahedra, corners with nine equivalent MgCa8Mg4 cuboctahedra, edges with ten CaCa5Mg7 cuboctahedra, faces with three equivalent MgCa8Mg4 cuboctahedra, and faces with nine CaCa5Mg7 cuboctahedra. There are a spread of Ca–Ca bond distances ranging from 3.47–3.75 Å. There are a spread of Ca–Mg bond distances ranging from 3.49–3.67 Å. In the second Ca site, Ca is bonded to five Ca and seven Mg atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with nine equivalent CaCa5Mg7 cuboctahedra, corners with nine equivalent MgCa8Mg4 cuboctahedra, edges with ten CaCa5Mg7 cuboctahedra, faces with three equivalent MgCa8Mg4 cuboctahedra, and faces with nine CaCa5Mg7 cuboctahedra. Both Ca–Ca bond lengths are 3.62 Å. There are a spread of Ca–Mg bond distances ranging from 3.49–3.67 Å. In the third Ca site, Ca is bonded to four Ca and eight Mg atoms to form distorted CaCa4Mg8 cuboctahedra that share edges with four equivalent MgCa8Mg4 cuboctahedra, edges with fourteen CaCa5Mg7 cuboctahedra, faces with four equivalent MgCa8Mg4 cuboctahedra, and faces with ten CaCa5Mg7 cuboctahedra. There are a spread of Ca–Mg bond distances ranging from 3.38–3.66 Å. There are two inequivalent Mg sites. In the first Mg site, Mg is bonded to eight Ca and four equivalent Mg atoms to form distorted MgCa8Mg4 cuboctahedra that share corners with eighteen CaCa5Mg7 cuboctahedra, edges with four equivalent CaCa4Mg8 cuboctahedra, edges with six equivalent MgCa8Mg4 cuboctahedra, faces with two equivalent MgCa8Mg4 cuboctahedra, and faces with ten CaCa5Mg7 cuboctahedra. All Mg–Mg bond lengths are 3.48 Å. In the second Mg site, Mg is bonded in a 12-coordinate geometry to seven Ca and two equivalent Mg atoms.