Mg2Si3 crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to one Si(1), one Si(10), two equivalent Si(11), two equivalent Si(3), and two equivalent Si(6) atoms. In the second Mg site, Mg(2) is bonded in a 7-coordinate geometry to one Si(9), two equivalent Si(12), two equivalent Si(4), and two equivalent Si(5) atoms. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to one Si(1), one Si(3), two equivalent Si(11), and two equivalent Si(2) atoms. In the fourth Mg site, Mg(4) is bonded to one Si(4), two equivalent Si(1), and two equivalent Si(12) atoms to form distorted edge-sharing MgSi5 square pyramids. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(4), two equivalent Si(12), and two equivalent Si(9) atoms. In the sixth Mg site, Mg(6) is bonded in a 8-coordinate geometry to one Si(3), one Si(8), two equivalent Si(10), two equivalent Si(11), and two equivalent Si(6) atoms. In the seventh Mg site, Mg(7) is bonded in a 6-coordinate geometry to two equivalent Si(7), two equivalent Si(8), and two equivalent Si(9) atoms. In the eighth Mg site, Mg(8) is bonded in a 6-coordinate geometry to one Si(10), one Si(8), two equivalent Si(6), and two equivalent Si(7) atoms. There are twelve inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), two equivalent Mg(4), one Si(2), and two equivalent Si(3) atoms. In the second Si site, Si(2) is bonded in a 5-coordinate geometry to two equivalent Mg(3), one Si(1), and two equivalent Si(4) atoms. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(3), one Mg(6), two equivalent Mg(1), two equivalent Si(1), and two equivalent Si(11) atoms. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(4), one Mg(5), two equivalent Mg(2), one Si(12), and two equivalent Si(2) atoms. In the fifth Si site, Si(5) is bonded in a 5-coordinate geometry to two equivalent Mg(2), one Si(7), and two equivalent Si(9) atoms. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Mg(6), two equivalent Mg(8), one Si(11), and two equivalent Si(10) atoms. In the seventh Si site, Si(7) is bonded in a 6-coordinate geometry to two equivalent Mg(7), two equivalent Mg(8), one Si(5), and one Si(8) atom. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(6), one Mg(8), two equivalent Mg(7), one Si(7), and two equivalent Si(10) atoms. In the ninth Si site, Si(9) is bonded in a 7-coordinate geometry to one Mg(2), two equivalent Mg(5), two equivalent Mg(7), and two equivalent Si(5) atoms. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(8), two equivalent Mg(6), two equivalent Si(6), and two equivalent Si(8) atoms. In the eleventh Si site, Si(11) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(6), one Si(6), and two equivalent Si(3) atoms. In the twelfth Si site, Si(12) is bonded in a 7-coordinate geometry to two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), and one Si(4) atom.
Mg2Si3 crystallizes in the triclinic P1 space group. There are eight inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 8-coordinate geometry to one Si(1), one Si(10), two equivalent Si(11), two equivalent Si(3), and two equivalent Si(6) atoms. The Mg(1)-Si(1) bond length is 2.83 Å. The Mg(1)-Si(10) bond length is 2.69 Å. There is one shorter (2.87 Å) and one longer (2.88 Å) Mg(1)-Si(11) bond length. Both Mg(1)-Si(3) bond lengths are 2.89 Å. Both Mg(1)-Si(6) bond lengths are 3.07 Å. In the second Mg site, Mg(2) is bonded in a 7-coordinate geometry to one Si(9), two equivalent Si(12), two equivalent Si(4), and two equivalent Si(5) atoms. The Mg(2)-Si(9) bond length is 2.89 Å. There is one shorter (2.79 Å) and one longer (2.80 Å) Mg(2)-Si(12) bond length. There is one shorter (2.99 Å) and one longer (3.02 Å) Mg(2)-Si(4) bond length. There is one shorter (2.74 Å) and one longer (2.75 Å) Mg(2)-Si(5) bond length. In the third Mg site, Mg(3) is bonded in a 6-coordinate geometry to one Si(1), one Si(3), two equivalent Si(11), and two equivalent Si(2) atoms. The Mg(3)-Si(1) bond length is 2.74 Å. The Mg(3)-Si(3) bond length is 2.78 Å. There is one shorter (2.94 Å) and one longer (2.96 Å) Mg(3)-Si(11) bond length. There is one shorter (2.80 Å) and one longer (2.81 Å) Mg(3)-Si(2) bond length. In the fourth Mg site, Mg(4) is bonded to one Si(4), two equivalent Si(1), and two equivalent Si(12) atoms to form distorted edge-sharing MgSi5 square pyramids. The Mg(4)-Si(4) bond length is 2.91 Å. There is one shorter (2.84 Å) and one longer (2.85 Å) Mg(4)-Si(1) bond length. There is one shorter (2.75 Å) and one longer (2.76 Å) Mg(4)-Si(12) bond length. In the fifth Mg site, Mg(5) is bonded in a 5-coordinate geometry to one Si(4), two equivalent Si(12), and two equivalent Si(9) atoms. The Mg(5)-Si(4) bond length is 2.79 Å. There is one shorter (2.79 Å) and one longer (2.82 Å) Mg(5)-Si(12) bond length. There is one shorter (2.82 Å) and one longer (2.84 Å) Mg(5)-Si(9) bond length. In the sixth Mg site, Mg(6) is bonded in a 8-coordinate geometry to one Si(3), one Si(8), two equivalent Si(10), two equivalent Si(11), and two equivalent Si(6) atoms. The Mg(6)-Si(3) bond length is 2.70 Å. The Mg(6)-Si(8) bond length is 2.89 Å. There is one shorter (2.89 Å) and one longer (2.91 Å) Mg(6)-Si(10) bond length. There is one shorter (3.03 Å) and one longer (3.06 Å) Mg(6)-Si(11) bond length. There is one shorter (2.90 Å) and one longer (2.91 Å) Mg(6)-Si(6) bond length. In the seventh Mg site, Mg(7) is bonded in a 6-coordinate geometry to two equivalent Si(7), two equivalent Si(8), and two equivalent Si(9) atoms. There is one shorter (2.91 Å) and one longer (3.02 Å) Mg(7)-Si(7) bond length. There is one shorter (3.01 Å) and one longer (3.17 Å) Mg(7)-Si(8) bond length. There is one shorter (2.80 Å) and one longer (2.89 Å) Mg(7)-Si(9) bond length. In the eighth Mg site, Mg(8) is bonded in a 6-coordinate geometry to one Si(10), one Si(8), two equivalent Si(6), and two equivalent Si(7) atoms. The Mg(8)-Si(10) bond length is 2.91 Å. The Mg(8)-Si(8) bond length is 2.65 Å. There is one shorter (2.92 Å) and one longer (3.10 Å) Mg(8)-Si(6) bond length. There is one shorter (2.69 Å) and one longer (2.73 Å) Mg(8)-Si(7) bond length. There are twelve inequivalent Si sites. In the first Si site, Si(1) is bonded in a 7-coordinate geometry to one Mg(1), one Mg(3), two equivalent Mg(4), one Si(2), and two equivalent Si(3) atoms. The Si(1)-Si(2) bond length is 2.44 Å. There is one shorter (2.48 Å) and one longer (2.49 Å) Si(1)-Si(3) bond length. In the second Si site, Si(2) is bonded in a 5-coordinate geometry to two equivalent Mg(3), one Si(1), and two equivalent Si(4) atoms. Both Si(2)-Si(4) bond lengths are 2.37 Å. In the third Si site, Si(3) is bonded in a 8-coordinate geometry to one Mg(3), one Mg(6), two equivalent Mg(1), two equivalent Si(1), and two equivalent Si(11) atoms. There is one shorter (2.56 Å) and one longer (2.57 Å) Si(3)-Si(11) bond length. In the fourth Si site, Si(4) is bonded in a 7-coordinate geometry to one Mg(4), one Mg(5), two equivalent Mg(2), one Si(12), and two equivalent Si(2) atoms. The Si(4)-Si(12) bond length is 2.39 Å. In the fifth Si site, Si(5) is bonded in a 5-coordinate geometry to two equivalent Mg(2), one Si(7), and two equivalent Si(9) atoms. The Si(5)-Si(7) bond length is 2.34 Å. Both Si(5)-Si(9) bond lengths are 2.40 Å. In the sixth Si site, Si(6) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Mg(6), two equivalent Mg(8), one Si(11), and two equivalent Si(10) atoms. The Si(6)-Si(11) bond length is 2.45 Å. There is one shorter (2.50 Å) and one longer (2.53 Å) Si(6)-Si(10) bond length. In the seventh Si site, Si(7) is bonded in a 6-coordinate geometry to two equivalent Mg(7), two equivalent Mg(8), one Si(5), and one Si(8) atom. The Si(7)-Si(8) bond length is 2.35 Å. In the eighth Si site, Si(8) is bonded in a 7-coordinate geometry to one Mg(6), one Mg(8), two equivalent Mg(7), one Si(7), and two equivalent Si(10) atoms. There is one shorter (2.50 Å) and one longer (2.54 Å) Si(8)-Si(10) bond length. In the ninth Si site, Si(9) is bonded in a 7-coordinate geometry to one Mg(2), two equivalent Mg(5), two equivalent Mg(7), and two equivalent Si(5) atoms. In the tenth Si site, Si(10) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(8), two equivalent Mg(6), two equivalent Si(6), and two equivalent Si(8) atoms. In the eleventh Si site, Si(11) is bonded in a 9-coordinate geometry to two equivalent Mg(1), two equivalent Mg(3), two equivalent Mg(6), one Si(6), and two equivalent Si(3) atoms. In the twelfth Si site, Si(12) is bonded in a 7-coordinate geometry to two equivalent Mg(2), two equivalent Mg(4), two equivalent Mg(5), and one Si(4) atom.