Sr(ErSe2)2 crystallizes in the orthorhombic Pnma space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(4) atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-62°. In the second Er site, Er(2) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-62°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Sr(1), one Er(2), and two equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeSr2Er3 trigonal bipyramids. In the second Se site, Se(2) is bonded to two equivalent Sr(1) and three equivalent Er(2) atoms to form a mixture of corner and edge-sharing SeSr2Er3 square pyramids. In the third Se site, Se(3) is bonded to two equivalent Sr(1), one Er(1), and two equivalent Er(2) atoms to form a mixture of distorted corner and edge-sharing SeSr2Er3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to two equivalent Sr(1) and three equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeSr2Er3 trigonal bipyramids.
Sr(ErSe2)2 crystallizes in the orthorhombic Pnma space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms. Both Sr(1)-Se(1) bond lengths are 3.23 Å. Both Sr(1)-Se(2) bond lengths are 3.20 Å. There is one shorter (3.41 Å) and one longer (3.44 Å) Sr(1)-Se(3) bond length. Both Sr(1)-Se(4) bond lengths are 3.24 Å. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded to one Se(3), two equivalent Se(1), and three equivalent Se(4) atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-62°. The Er(1)-Se(3) bond length is 2.81 Å. Both Er(1)-Se(1) bond lengths are 2.86 Å. There is one shorter (2.80 Å) and two longer (2.84 Å) Er(1)-Se(4) bond lengths. In the second Er site, Er(2) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(2) atoms to form a mixture of corner and edge-sharing ErSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-62°. The Er(2)-Se(1) bond length is 2.86 Å. Both Er(2)-Se(3) bond lengths are 2.78 Å. There is one shorter (2.83 Å) and two longer (2.85 Å) Er(2)-Se(2) bond lengths. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Sr(1), one Er(2), and two equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeSr2Er3 trigonal bipyramids. In the second Se site, Se(2) is bonded to two equivalent Sr(1) and three equivalent Er(2) atoms to form a mixture of corner and edge-sharing SeSr2Er3 square pyramids. In the third Se site, Se(3) is bonded to two equivalent Sr(1), one Er(1), and two equivalent Er(2) atoms to form a mixture of distorted corner and edge-sharing SeSr2Er3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to two equivalent Sr(1) and three equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeSr2Er3 trigonal bipyramids.