Mg9Sn5 crystallizes in the trigonal R3 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Sn(4), one Sn(5), and two equivalent Sn(6) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. In the second Mg site, Mg(2) is bonded to one Sn(3), one Sn(6), and two equivalent Sn(5) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Sn(2), one Sn(4), one Sn(6), and two equivalent Sn(5) atoms. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Sn(1), one Sn(3), one Sn(5), and two equivalent Sn(6) atoms. In the fifth Mg site, Mg(5) is bonded to one Sn(2), one Sn(5), and two equivalent Sn(6) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. In the sixth Mg site, Mg(6) is bonded to one Sn(1), one Sn(6), and two equivalent Sn(5) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. There are six inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 6-coordinate geometry to three equivalent Mg(4) and three equivalent Mg(6) atoms. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to three equivalent Mg(3) and three equivalent Mg(5) atoms. In the third Sn site, Sn(3) is bonded in a 6-coordinate geometry to three equivalent Mg(2) and three equivalent Mg(4) atoms. In the fourth Sn site, Sn(4) is bonded in a 6-coordinate geometry to three equivalent Mg(1) and three equivalent Mg(3) atoms. In the fifth Sn site, Sn(5) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(6) atoms. In the sixth Sn site, Sn(6) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), one Mg(6), two equivalent Mg(1), two equivalent Mg(4), and two equivalent Mg(5) atoms.
Mg9Sn5 crystallizes in the trigonal R3 space group. There are six inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one Sn(4), one Sn(5), and two equivalent Sn(6) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. The Mg(1)-Sn(4) bond length is 2.87 Å. The Mg(1)-Sn(5) bond length is 2.96 Å. There is one shorter (2.94 Å) and one longer (3.02 Å) Mg(1)-Sn(6) bond length. In the second Mg site, Mg(2) is bonded to one Sn(3), one Sn(6), and two equivalent Sn(5) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. The Mg(2)-Sn(3) bond length is 2.87 Å. The Mg(2)-Sn(6) bond length is 2.93 Å. There is one shorter (2.93 Å) and one longer (2.97 Å) Mg(2)-Sn(5) bond length. In the third Mg site, Mg(3) is bonded in a 5-coordinate geometry to one Sn(2), one Sn(4), one Sn(6), and two equivalent Sn(5) atoms. The Mg(3)-Sn(2) bond length is 3.10 Å. The Mg(3)-Sn(4) bond length is 2.98 Å. The Mg(3)-Sn(6) bond length is 2.98 Å. There is one shorter (3.03 Å) and one longer (3.09 Å) Mg(3)-Sn(5) bond length. In the fourth Mg site, Mg(4) is bonded in a 5-coordinate geometry to one Sn(1), one Sn(3), one Sn(5), and two equivalent Sn(6) atoms. The Mg(4)-Sn(1) bond length is 2.99 Å. The Mg(4)-Sn(3) bond length is 3.08 Å. The Mg(4)-Sn(5) bond length is 2.97 Å. There is one shorter (3.04 Å) and one longer (3.10 Å) Mg(4)-Sn(6) bond length. In the fifth Mg site, Mg(5) is bonded to one Sn(2), one Sn(5), and two equivalent Sn(6) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. The Mg(5)-Sn(2) bond length is 2.86 Å. The Mg(5)-Sn(5) bond length is 2.95 Å. There is one shorter (2.94 Å) and one longer (2.96 Å) Mg(5)-Sn(6) bond length. In the sixth Mg site, Mg(6) is bonded to one Sn(1), one Sn(6), and two equivalent Sn(5) atoms to form a mixture of distorted corner and edge-sharing MgSn4 tetrahedra. The Mg(6)-Sn(1) bond length is 2.86 Å. The Mg(6)-Sn(6) bond length is 2.94 Å. There is one shorter (2.96 Å) and one longer (3.05 Å) Mg(6)-Sn(5) bond length. There are six inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 6-coordinate geometry to three equivalent Mg(4) and three equivalent Mg(6) atoms. In the second Sn site, Sn(2) is bonded in a 6-coordinate geometry to three equivalent Mg(3) and three equivalent Mg(5) atoms. In the third Sn site, Sn(3) is bonded in a 6-coordinate geometry to three equivalent Mg(2) and three equivalent Mg(4) atoms. In the fourth Sn site, Sn(4) is bonded in a 6-coordinate geometry to three equivalent Mg(1) and three equivalent Mg(3) atoms. In the fifth Sn site, Sn(5) is bonded in a 9-coordinate geometry to one Mg(1), one Mg(4), one Mg(5), two equivalent Mg(2), two equivalent Mg(3), and two equivalent Mg(6) atoms. In the sixth Sn site, Sn(6) is bonded in a 9-coordinate geometry to one Mg(2), one Mg(3), one Mg(6), two equivalent Mg(1), two equivalent Mg(4), and two equivalent Mg(5) atoms.