Er3Sn7 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Sn(1), and four equivalent Sn(2) atoms. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to two equivalent Sn(3) and four equivalent Sn(4) atoms. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 10-coordinate geometry to four equivalent Er(1), two equivalent Sn(1), and four equivalent Sn(3) atoms. In the second Sn site, Sn(2) is bonded in a 2-coordinate geometry to two equivalent Er(1), two equivalent Sn(4), and four equivalent Sn(3) atoms. In the third Sn site, Sn(3) is bonded in a 10-coordinate geometry to two equivalent Er(2), two equivalent Sn(1), two equivalent Sn(3), and four equivalent Sn(2) atoms. In the fourth Sn site, Sn(4) is bonded in a 10-coordinate geometry to four equivalent Er(2), two equivalent Sn(2), and four equivalent Sn(4) atoms.
Er3Sn7 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 10-coordinate geometry to two equivalent Er(1), four equivalent Sn(1), and four equivalent Sn(2) atoms. Both Er(1)-Er(1) bond lengths are 3.12 Å. All Er(1)-Sn(1) bond lengths are 3.32 Å. All Er(1)-Sn(2) bond lengths are 3.29 Å. In the second Er site, Er(2) is bonded in a 6-coordinate geometry to two equivalent Sn(3) and four equivalent Sn(4) atoms. Both Er(2)-Sn(3) bond lengths are 3.26 Å. All Er(2)-Sn(4) bond lengths are 3.32 Å. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a 10-coordinate geometry to four equivalent Er(1), two equivalent Sn(1), and four equivalent Sn(3) atoms. Both Sn(1)-Sn(1) bond lengths are 3.12 Å. All Sn(1)-Sn(3) bond lengths are 3.34 Å. In the second Sn site, Sn(2) is bonded in a 2-coordinate geometry to two equivalent Er(1), two equivalent Sn(4), and four equivalent Sn(3) atoms. Both Sn(2)-Sn(4) bond lengths are 3.40 Å. All Sn(2)-Sn(3) bond lengths are 3.32 Å. In the third Sn site, Sn(3) is bonded in a 10-coordinate geometry to two equivalent Er(2), two equivalent Sn(1), two equivalent Sn(3), and four equivalent Sn(2) atoms. Both Sn(3)-Sn(3) bond lengths are 3.12 Å. In the fourth Sn site, Sn(4) is bonded in a 10-coordinate geometry to four equivalent Er(2), two equivalent Sn(2), and four equivalent Sn(4) atoms. There are two shorter (3.12 Å) and two longer (3.28 Å) Sn(4)-Sn(4) bond lengths.