Mg2Ca crystallizes in the orthorhombic Amm2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Mg(1), two equivalent Mg(4), and four equivalent Mg(3) atoms to form a mixture of distorted face and corner-sharing CaMg8 cuboctahedra. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent Mg(3), two equivalent Mg(4), and four equivalent Mg(2) atoms. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to two equivalent Ca(1), two equivalent Mg(2), and four equivalent Mg(4) atoms. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to four equivalent Ca(2), two equivalent Mg(1), and two equivalent Mg(4) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to two equivalent Ca(2) and four equivalent Ca(1) atoms. In the fourth Mg site, Mg(4) is bonded in a 10-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), two equivalent Mg(2), and four equivalent Mg(1) atoms.
Mg2Ca crystallizes in the orthorhombic Amm2 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to two equivalent Mg(1), two equivalent Mg(4), and four equivalent Mg(3) atoms to form a mixture of distorted face and corner-sharing CaMg8 cuboctahedra. Both Ca(1)-Mg(1) bond lengths are 3.42 Å. Both Ca(1)-Mg(4) bond lengths are 3.43 Å. All Ca(1)-Mg(3) bond lengths are 3.45 Å. In the second Ca site, Ca(2) is bonded in a 8-coordinate geometry to two equivalent Mg(3), two equivalent Mg(4), and four equivalent Mg(2) atoms. Both Ca(2)-Mg(3) bond lengths are 3.45 Å. Both Ca(2)-Mg(4) bond lengths are 3.32 Å. All Ca(2)-Mg(2) bond lengths are 3.38 Å. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to two equivalent Ca(1), two equivalent Mg(2), and four equivalent Mg(4) atoms. Both Mg(1)-Mg(2) bond lengths are 3.24 Å. All Mg(1)-Mg(4) bond lengths are 3.36 Å. In the second Mg site, Mg(2) is bonded in a 8-coordinate geometry to four equivalent Ca(2), two equivalent Mg(1), and two equivalent Mg(4) atoms. Both Mg(2)-Mg(4) bond lengths are 3.29 Å. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to two equivalent Ca(2) and four equivalent Ca(1) atoms. In the fourth Mg site, Mg(4) is bonded in a 10-coordinate geometry to two equivalent Ca(1), two equivalent Ca(2), two equivalent Mg(2), and four equivalent Mg(1) atoms.