MgCa crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four equivalent Ca(2), two equivalent Mg(2), and six equivalent Mg(1) atoms to form distorted CaCa4Mg8 cuboctahedra that share corners with six equivalent Ca(1)Ca4Mg8 cuboctahedra, edges with six equivalent Ca(1)Ca4Mg8 cuboctahedra, edges with eight equivalent Ca(2)Ca5Mg7 cuboctahedra, and faces with eight equivalent Ca(2)Ca5Mg7 cuboctahedra. In the second Ca site, Ca(2) is bonded to two equivalent Ca(1), three equivalent Ca(2), three equivalent Mg(2), and four equivalent Mg(1) atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with twelve equivalent Ca(2)Ca5Mg7 cuboctahedra, edges with four equivalent Ca(1)Ca4Mg8 cuboctahedra, edges with six equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with four equivalent Ca(1)Ca4Mg8 cuboctahedra, and faces with four equivalent Ca(2)Ca5Mg7 cuboctahedra. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 7-coordinate geometry to three equivalent Ca(1) and four equivalent Ca(2) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Ca(1) and six equivalent Ca(2) atoms.
MgCa crystallizes in the monoclinic C2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to four equivalent Ca(2), two equivalent Mg(2), and six equivalent Mg(1) atoms to form distorted CaCa4Mg8 cuboctahedra that share corners with six equivalent Ca(1)Ca4Mg8 cuboctahedra, edges with six equivalent Ca(1)Ca4Mg8 cuboctahedra, edges with eight equivalent Ca(2)Ca5Mg7 cuboctahedra, and faces with eight equivalent Ca(2)Ca5Mg7 cuboctahedra. There are two shorter (3.62 Å) and two longer (3.69 Å) Ca(1)-Ca(2) bond lengths. Both Ca(1)-Mg(2) bond lengths are 3.42 Å. There are a spread of Ca(1)-Mg(1) bond distances ranging from 3.44-3.70 Å. In the second Ca site, Ca(2) is bonded to two equivalent Ca(1), three equivalent Ca(2), three equivalent Mg(2), and four equivalent Mg(1) atoms to form distorted CaCa5Mg7 cuboctahedra that share corners with twelve equivalent Ca(2)Ca5Mg7 cuboctahedra, edges with four equivalent Ca(1)Ca4Mg8 cuboctahedra, edges with six equivalent Ca(2)Ca5Mg7 cuboctahedra, faces with four equivalent Ca(1)Ca4Mg8 cuboctahedra, and faces with four equivalent Ca(2)Ca5Mg7 cuboctahedra. There is one shorter (3.49 Å) and two longer (3.58 Å) Ca(2)-Ca(2) bond lengths. There are a spread of Ca(2)-Mg(2) bond distances ranging from 3.49-3.58 Å. There are a spread of Ca(2)-Mg(1) bond distances ranging from 3.45-3.64 Å. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 7-coordinate geometry to three equivalent Ca(1) and four equivalent Ca(2) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to two equivalent Ca(1) and six equivalent Ca(2) atoms.