Er3Sn7 crystallizes in the orthorhombic Cmmm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to four equivalent Sn(1), four equivalent Sn(2), and four equivalent Sn(3) atoms to form a mixture of face and corner-sharing ErSn12 cuboctahedra. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to two equivalent Sn(2), two equivalent Sn(3), and six equivalent Sn(4) atoms. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a square co-planar geometry to four equivalent Er(1), four equivalent Sn(2), and four equivalent Sn(3) atoms. In the second Sn site, Sn(2) is bonded in a 10-coordinate geometry to two equivalent Er(1), two equivalent Er(2), two equivalent Sn(1), and four equivalent Sn(3) atoms. In the third Sn site, Sn(3) is bonded in a 10-coordinate geometry to two equivalent Er(1), two equivalent Er(2), two equivalent Sn(1), and four equivalent Sn(2) atoms. In the fourth Sn site, Sn(4) is bonded in a 8-coordinate geometry to six equivalent Er(2) and two 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 to four equivalent Sn(1), four equivalent Sn(2), and four equivalent Sn(3) atoms to form a mixture of face and corner-sharing ErSn12 cuboctahedra. All Er(1)-Sn(1) bond lengths are 3.10 Å. All Er(1)-Sn(2) bond lengths are 3.36 Å. All Er(1)-Sn(3) bond lengths are 3.38 Å. In the second Er site, Er(2) is bonded in a 10-coordinate geometry to two equivalent Sn(2), two equivalent Sn(3), and six equivalent Sn(4) atoms. Both Er(2)-Sn(2) bond lengths are 3.28 Å. Both Er(2)-Sn(3) bond lengths are 3.26 Å. There are four shorter (3.16 Å) and two longer (3.43 Å) Er(2)-Sn(4) bond lengths. There are four inequivalent Sn sites. In the first Sn site, Sn(1) is bonded in a square co-planar geometry to four equivalent Er(1), four equivalent Sn(2), and four equivalent Sn(3) atoms. All Sn(1)-Sn(2) bond lengths are 3.38 Å. All Sn(1)-Sn(3) bond lengths are 3.36 Å. In the second Sn site, Sn(2) is bonded in a 10-coordinate geometry to two equivalent Er(1), two equivalent Er(2), two equivalent Sn(1), and four equivalent Sn(3) atoms. All Sn(2)-Sn(3) bond lengths are 3.10 Å. In the third Sn site, Sn(3) is bonded in a 10-coordinate geometry to two equivalent Er(1), two equivalent Er(2), two equivalent Sn(1), and four equivalent Sn(2) atoms. In the fourth Sn site, Sn(4) is bonded in a 8-coordinate geometry to six equivalent Er(2) and two equivalent Sn(4) atoms. Both Sn(4)-Sn(4) bond lengths are 2.96 Å.