Cu2GeSe3 is Enargite-like structured and crystallizes in the orthorhombic Fdd2 space group. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with five equivalent Ge(1)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with four equivalent Cu(1)Se4 tetrahedra, and corners with six equivalent Ge(1)Se4 tetrahedra. In the third Cu site, Cu(3) is bonded to two equivalent Se(2) and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(2)Se4 tetrahedra, corners with four equivalent Ge(1)Se4 tetrahedra, and corners with six equivalent Cu(1)Se4 tetrahedra. Ge(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form GeSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with five equivalent Cu(1)Se4 tetrahedra. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cu(1), one Cu(2), and two equivalent Ge(1) atoms to form SeCu2Ge2 tetrahedra that share corners with three equivalent Se(1)Cu2Ge2 tetrahedra, corners with four equivalent Se(3)Cu3Ge tetrahedra, and corners with five equivalent Se(2)Cu3Ge tetrahedra. In the second Se site, Se(2) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Ge(1) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with five equivalent Se(1)Cu2Ge2 tetrahedra, and corners with five equivalent Se(3)Cu3Ge tetrahedra. In the third Se site, Se(3) is bonded to one Cu(3), two equivalent Cu(1), and one Ge(1) atom to form SeCu3Ge tetrahedra that share corners with three equivalent Se(3)Cu3Ge tetrahedra, corners with four equivalent Se(1)Cu2Ge2 tetrahedra, and corners with five equivalent Se(2)Cu3Ge tetrahedra.
Cu2GeSe3 is Enargite-like structured and crystallizes in the orthorhombic Fdd2 space group. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Se(1), one Se(2), and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with five equivalent Ge(1)Se4 tetrahedra. The Cu(1)-Se(1) bond length is 2.44 Å. The Cu(1)-Se(2) bond length is 2.42 Å. There is one shorter (2.40 Å) and one longer (2.41 Å) Cu(1)-Se(3) bond length. In the second Cu site, Cu(2) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with four equivalent Cu(1)Se4 tetrahedra, and corners with six equivalent Ge(1)Se4 tetrahedra. Both Cu(2)-Se(1) bond lengths are 2.44 Å. Both Cu(2)-Se(2) bond lengths are 2.41 Å. In the third Cu site, Cu(3) is bonded to two equivalent Se(2) and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(2)Se4 tetrahedra, corners with four equivalent Ge(1)Se4 tetrahedra, and corners with six equivalent Cu(1)Se4 tetrahedra. Both Cu(3)-Se(2) bond lengths are 2.40 Å. Both Cu(3)-Se(3) bond lengths are 2.40 Å. Ge(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form GeSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with five equivalent Cu(1)Se4 tetrahedra. The Ge(1)-Se(2) bond length is 2.41 Å. The Ge(1)-Se(3) bond length is 2.41 Å. There is one shorter (2.52 Å) and one longer (2.53 Å) Ge(1)-Se(1) bond length. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cu(1), one Cu(2), and two equivalent Ge(1) atoms to form SeCu2Ge2 tetrahedra that share corners with three equivalent Se(1)Cu2Ge2 tetrahedra, corners with four equivalent Se(3)Cu3Ge tetrahedra, and corners with five equivalent Se(2)Cu3Ge tetrahedra. In the second Se site, Se(2) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Ge(1) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with five equivalent Se(1)Cu2Ge2 tetrahedra, and corners with five equivalent Se(3)Cu3Ge tetrahedra. In the third Se site, Se(3) is bonded to one Cu(3), two equivalent Cu(1), and one Ge(1) atom to form SeCu3Ge tetrahedra that share corners with three equivalent Se(3)Cu3Ge tetrahedra, corners with four equivalent Se(1)Cu2Ge2 tetrahedra, and corners with five equivalent Se(2)Cu3Ge tetrahedra.