Mg2Si3 is Magnesium tetraboride-like structured and crystallizes in the monoclinic C2/m space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Si(1), one Si(5), two equivalent Si(2), two equivalent Si(3), and two equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 3-coordinate geometry to one Si(6) and five equivalent Si(1) atoms. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to one Si(2), one Si(4), two equivalent Si(3), two equivalent Si(5), and two equivalent Si(6) atoms. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(5), two equivalent Si(3), and three equivalent Si(4) atoms. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), five equivalent Mg(2), one Si(1), and two equivalent Si(2) atoms. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to one Mg(3), two equivalent Mg(1), two equivalent Si(1), and two equivalent Si(6) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(4), one Si(6), and two equivalent Si(5) atoms. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(3), three equivalent Mg(4), one Si(4), and two equivalent Si(5) atoms. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(4), two equivalent Mg(3), two equivalent Si(3), and two equivalent Si(4) atoms. In the sixth Si site, Si(6) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(1), two equivalent Mg(3), one Si(3), and two equivalent Si(2) atoms.
Mg2Si3 is Magnesium tetraboride-like structured and crystallizes in the monoclinic C2/m space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 6-coordinate geometry to one Si(1), one Si(5), two equivalent Si(2), two equivalent Si(3), and two equivalent Si(6) atoms. The Mg(1)-Si(1) bond length is 2.86 Å. The Mg(1)-Si(5) bond length is 2.85 Å. Both Mg(1)-Si(2) bond lengths are 2.89 Å. Both Mg(1)-Si(3) bond lengths are 3.16 Å. Both Mg(1)-Si(6) bond lengths are 2.86 Å. In the second Mg site, Mg(2) is bonded in a 3-coordinate geometry to one Si(6) and five equivalent Si(1) atoms. The Mg(2)-Si(6) bond length is 2.65 Å. There are a spread of Mg(2)-Si(1) bond distances ranging from 2.77-3.20 Å. In the third Mg site, Mg(3) is bonded in a 8-coordinate geometry to one Si(2), one Si(4), two equivalent Si(3), two equivalent Si(5), and two equivalent Si(6) atoms. The Mg(3)-Si(2) bond length is 2.77 Å. The Mg(3)-Si(4) bond length is 2.99 Å. Both Mg(3)-Si(3) bond lengths are 2.90 Å. Both Mg(3)-Si(5) bond lengths are 2.78 Å. Both Mg(3)-Si(6) bond lengths are 2.88 Å. In the fourth Mg site, Mg(4) is bonded in a 6-coordinate geometry to one Si(5), two equivalent Si(3), and three equivalent Si(4) atoms. The Mg(4)-Si(5) bond length is 2.77 Å. Both Mg(4)-Si(3) bond lengths are 2.88 Å. There is one shorter (2.80 Å) and two longer (2.85 Å) Mg(4)-Si(4) bond lengths. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Mg(1), five equivalent Mg(2), one Si(1), and two equivalent Si(2) atoms. The Si(1)-Si(1) bond length is 2.44 Å. Both Si(1)-Si(2) bond lengths are 2.54 Å. In the second Si site, Si(2) is bonded in a 7-coordinate geometry to one Mg(3), two equivalent Mg(1), two equivalent Si(1), and two equivalent Si(6) atoms. Both Si(2)-Si(6) bond lengths are 2.50 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(4), one Si(6), and two equivalent Si(5) atoms. The Si(3)-Si(6) bond length is 2.44 Å. Both Si(3)-Si(5) bond lengths are 2.53 Å. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(3), three equivalent Mg(4), one Si(4), and two equivalent Si(5) atoms. The Si(4)-Si(4) bond length is 2.48 Å. Both Si(4)-Si(5) bond lengths are 2.51 Å. In the fifth Si site, Si(5) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(4), two equivalent Mg(3), two equivalent Si(3), and two equivalent Si(4) atoms. In the sixth Si site, Si(6) is bonded in a 8-coordinate geometry to one Mg(2), two equivalent Mg(1), two equivalent Mg(3), one Si(3), and two equivalent Si(2) atoms.