Mg2Si crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent Mg(2) and five equivalent Si(1) atoms to form a mixture of distorted corner and face-sharing MgMg6Si5 trigonal bipyramids. In the second Mg site, Mg(2) is bonded in a 14-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), and six equivalent Si(1) atoms. Si(1) is bonded in a 11-coordinate geometry to five equivalent Mg(1) and six equivalent Mg(2) atoms.
Mg2Si crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to six equivalent Mg(2) and five equivalent Si(1) atoms to form a mixture of distorted corner and face-sharing MgMg6Si5 trigonal bipyramids. All Mg(1)-Mg(2) bond lengths are 3.07 Å. There are three shorter (2.67 Å) and two longer (3.04 Å) Mg(1)-Si(1) bond lengths. In the second Mg site, Mg(2) is bonded in a 14-coordinate geometry to two equivalent Mg(2), six equivalent Mg(1), and six equivalent Si(1) atoms. Both Mg(2)-Mg(2) bond lengths are 3.04 Å. All Mg(2)-Si(1) bond lengths are 3.07 Å. Si(1) is bonded in a 11-coordinate geometry to five equivalent Mg(1) and six equivalent Mg(2) atoms.