Mg2Si crystallizes in the tetragonal P4/nmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent Si(1) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to five equivalent Si(1) atoms. Si(1) is bonded in a 9-coordinate geometry to four equivalent Mg(1) and five equivalent Mg(2) atoms.
Mg2Si crystallizes in the tetragonal P4/nmm space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to four equivalent Si(1) atoms to form a mixture of distorted edge and corner-sharing MgSi4 tetrahedra. All Mg(1)-Si(1) bond lengths are 2.73 Å. In the second Mg site, Mg(2) is bonded in a 5-coordinate geometry to five equivalent Si(1) atoms. There is one shorter (2.67 Å) and four longer (3.05 Å) Mg(2)-Si(1) bond lengths. Si(1) is bonded in a 9-coordinate geometry to four equivalent Mg(1) and five equivalent Mg(2) atoms.