Cu3SeO8 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted CuO6 octahedra that share corners with three equivalent Se(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. In the second Cu site, Cu(2) is bonded in a 6-coordinate geometry to one O(2), one O(5), and four equivalent O(6) atoms. Se(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SeO4 tetrahedra that share corners with six equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-59°. There are six inequivalent O sites. In the first O site, O(4) is bonded in a water-like geometry to two equivalent Cu(1) atoms. In the second O site, O(5) is bonded in a distorted water-like geometry to one Cu(2) and two equivalent Cu(1) atoms. In the third O site, O(6) is bonded in a trigonal non-coplanar geometry to one Cu(1) and two equivalent Cu(2) atoms. In the fourth O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(1) and one Se(1) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Cu(2), two equivalent Cu(1), and one Se(1) atom. In the sixth O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Cu(1) and one Se(1) atom.
Cu3SeO8 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form distorted CuO6 octahedra that share corners with three equivalent Se(1)O4 tetrahedra and edges with two equivalent Cu(1)O6 octahedra. The Cu(1)-O(1) bond length is 1.89 Å. The Cu(1)-O(2) bond length is 2.50 Å. The Cu(1)-O(3) bond length is 2.51 Å. The Cu(1)-O(4) bond length is 1.80 Å. The Cu(1)-O(5) bond length is 1.80 Å. The Cu(1)-O(6) bond length is 1.88 Å. In the second Cu site, Cu(2) is bonded in a 6-coordinate geometry to one O(2), one O(5), and four equivalent O(6) atoms. The Cu(2)-O(2) bond length is 2.39 Å. The Cu(2)-O(5) bond length is 2.41 Å. There are two shorter (1.89 Å) and two longer (1.92 Å) Cu(2)-O(6) bond lengths. Se(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SeO4 tetrahedra that share corners with six equivalent Cu(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 42-59°. The Se(1)-O(2) bond length is 1.67 Å. The Se(1)-O(3) bond length is 1.65 Å. Both Se(1)-O(1) bond lengths are 1.72 Å. There are six inequivalent O sites. In the first O site, O(4) is bonded in a water-like geometry to two equivalent Cu(1) atoms. In the second O site, O(5) is bonded in a distorted water-like geometry to one Cu(2) and two equivalent Cu(1) atoms. In the third O site, O(6) is bonded in a trigonal non-coplanar geometry to one Cu(1) and two equivalent Cu(2) atoms. In the fourth O site, O(1) is bonded in a bent 120 degrees geometry to one Cu(1) and one Se(1) atom. In the fifth O site, O(2) is bonded in a 4-coordinate geometry to one Cu(2), two equivalent Cu(1), and one Se(1) atom. In the sixth O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Cu(1) and one Se(1) atom.