Mg2Ca crystallizes in the monoclinic C2/c space group. Ca(1) is bonded to two equivalent Ca(1) and ten equivalent Mg(1) atoms to form CaCa2Mg10 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with twelve equivalent Mg(1)Ca5Mg7 cuboctahedra, edges with eight equivalent Mg(1)Ca5Mg7 cuboctahedra, edges with ten equivalent Ca(1)Ca2Mg10 cuboctahedra, faces with four equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with sixteen equivalent Mg(1)Ca5Mg7 cuboctahedra. Mg(1) is bonded to five equivalent Ca(1) and seven equivalent Mg(1) atoms to form distorted MgCa5Mg7 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with twelve equivalent Mg(1)Ca5Mg7 cuboctahedra, edges with four equivalent Ca(1)Ca2Mg10 cuboctahedra, edges with fourteen equivalent Mg(1)Ca5Mg7 cuboctahedra, faces with eight equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with twelve equivalent Mg(1)Ca5Mg7 cuboctahedra.
Mg2Ca crystallizes in the monoclinic C2/c space group. Ca(1) is bonded to two equivalent Ca(1) and ten equivalent Mg(1) atoms to form CaCa2Mg10 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with twelve equivalent Mg(1)Ca5Mg7 cuboctahedra, edges with eight equivalent Mg(1)Ca5Mg7 cuboctahedra, edges with ten equivalent Ca(1)Ca2Mg10 cuboctahedra, faces with four equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with sixteen equivalent Mg(1)Ca5Mg7 cuboctahedra. Both Ca(1)-Ca(1) bond lengths are 3.41 Å. There are a spread of Ca(1)-Mg(1) bond distances ranging from 3.36-3.53 Å. Mg(1) is bonded to five equivalent Ca(1) and seven equivalent Mg(1) atoms to form distorted MgCa5Mg7 cuboctahedra that share corners with six equivalent Ca(1)Ca2Mg10 cuboctahedra, corners with twelve equivalent Mg(1)Ca5Mg7 cuboctahedra, edges with four equivalent Ca(1)Ca2Mg10 cuboctahedra, edges with fourteen equivalent Mg(1)Ca5Mg7 cuboctahedra, faces with eight equivalent Ca(1)Ca2Mg10 cuboctahedra, and faces with twelve equivalent Mg(1)Ca5Mg7 cuboctahedra. There are a spread of Mg(1)-Mg(1) bond distances ranging from 3.38-3.47 Å.