CuFeSe2 is Sulvanite-like structured and crystallizes in the tetragonal P-42m space group. Fe(1) is bonded to four equivalent Se(1) atoms to form distorted FeSe4 tetrahedra that share corners with four equivalent Fe(1)Se4 tetrahedra, corners with four equivalent Cu(2)Se4 tetrahedra, and edges with two equivalent Cu(1)Se4 tetrahedra. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to four equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share edges with two equivalent Cu(2)Se4 tetrahedra and edges with four equivalent Fe(1)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to four equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with eight equivalent Fe(1)Se4 tetrahedra and edges with two equivalent Cu(1)Se4 tetrahedra. Se(1) is bonded to two equivalent Fe(1), one Cu(1), and one Cu(2) atom to form a mixture of distorted edge and corner-sharing SeFe2Cu2 tetrahedra.
CuFeSe2 is Sulvanite-like structured and crystallizes in the tetragonal P-42m space group. Fe(1) is bonded to four equivalent Se(1) atoms to form distorted FeSe4 tetrahedra that share corners with four equivalent Fe(1)Se4 tetrahedra, corners with four equivalent Cu(2)Se4 tetrahedra, and edges with two equivalent Cu(1)Se4 tetrahedra. All Fe(1)-Se(1) bond lengths are 2.40 Å. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to four equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share edges with two equivalent Cu(2)Se4 tetrahedra and edges with four equivalent Fe(1)Se4 tetrahedra. All Cu(1)-Se(1) bond lengths are 2.47 Å. In the second Cu site, Cu(2) is bonded to four equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with eight equivalent Fe(1)Se4 tetrahedra and edges with two equivalent Cu(1)Se4 tetrahedra. All Cu(2)-Se(1) bond lengths are 2.45 Å. Se(1) is bonded to two equivalent Fe(1), one Cu(1), and one Cu(2) atom to form a mixture of distorted edge and corner-sharing SeFe2Cu2 tetrahedra.