Ba(ErSe2)2 crystallizes in the orthorhombic Pnma space group. Ba(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 48-59°. 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 48-59°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to two equivalent Ba(1), one Er(2), and two equivalent Er(1) atoms. In the second Se site, Se(2) is bonded to two equivalent Ba(1) and three equivalent Er(2) atoms to form a mixture of corner and edge-sharing SeBa2Er3 square pyramids. In the third Se site, Se(3) is bonded to two equivalent Ba(1), one Er(1), and two equivalent Er(2) atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to two equivalent Ba(1) and three equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 trigonal bipyramids.
Ba(ErSe2)2 crystallizes in the orthorhombic Pnma space group. Ba(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 Ba(1)-Se(1) bond lengths are 3.40 Å. Both Ba(1)-Se(2) bond lengths are 3.32 Å. There is one shorter (3.47 Å) and one longer (3.50 Å) Ba(1)-Se(3) bond length. Both Ba(1)-Se(4) bond lengths are 3.33 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 48-59°. The Er(1)-Se(3) bond length is 2.85 Å. Both Er(1)-Se(1) bond lengths are 2.87 Å. There is one shorter (2.79 Å) and two longer (2.85 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 48-59°. The Er(2)-Se(1) bond length is 2.88 Å. Both Er(2)-Se(3) bond lengths are 2.81 Å. There is one shorter (2.83 Å) and two longer (2.86 Å) Er(2)-Se(2) bond lengths. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to two equivalent Ba(1), one Er(2), and two equivalent Er(1) atoms. In the second Se site, Se(2) is bonded to two equivalent Ba(1) and three equivalent Er(2) atoms to form a mixture of corner and edge-sharing SeBa2Er3 square pyramids. In the third Se site, Se(3) is bonded to two equivalent Ba(1), one Er(1), and two equivalent Er(2) atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 trigonal bipyramids. In the fourth Se site, Se(4) is bonded to two equivalent Ba(1) and three equivalent Er(1) atoms to form a mixture of distorted corner and edge-sharing SeBa2Er3 trigonal bipyramids.