Cu2GeSe3 is Enargite-like structured and crystallizes in the triclinic P1 space group. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Se(1), one Se(2), one Se(4), and one Se(6) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Ge(2)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with three equivalent Ge(1)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to one Se(1), one Se(2), one Se(4), and one Se(5) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Ge(2)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Ge(1)Se4 tetrahedra. In the third Cu site, Cu(3) is bonded to one Se(1), one Se(3), one Se(5), and one Se(6) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(4)Se4 tetrahedra, and corners with three equivalent Ge(2)Se4 tetrahedra. In the fourth Cu site, Cu(4) is bonded to one Se(2), one Se(3), one Se(5), and one Se(6) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Ge(2)Se4 tetrahedra. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Ge(2)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Cu(2)Se4 tetrahedra. In the second Ge site, Ge(2) is bonded to one Se(3), one Se(4), one Se(5), and one Se(6) atom to form GeSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Cu(4)Se4 tetrahedra. There are six inequivalent Se sites. In the first Se site, Se(1) 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(3)Cu2Ge2 tetrahedra, corners with two equivalent Se(5)Cu3Ge tetrahedra, corners with two equivalent Se(6)Cu3Ge tetrahedra, corners with three equivalent Se(4)Cu2Ge2 tetrahedra, and corners with three equivalent Se(2)Cu3Ge tetrahedra. In the second Se site, Se(2) is bonded to one Cu(1), one Cu(2), one Cu(4), and one Ge(1) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(3)Cu2Ge2 tetrahedra, corners with two equivalent Se(5)Cu3Ge tetrahedra, corners with two equivalent Se(6)Cu3Ge tetrahedra, corners with three equivalent Se(4)Cu2Ge2 tetrahedra, and corners with three equivalent Se(1)Cu3Ge tetrahedra. In the third Se site, Se(3) is bonded to one Cu(3), one Cu(4), one Ge(1), and one Ge(2) atom to form SeCu2Ge2 tetrahedra that share corners with two equivalent Se(4)Cu2Ge2 tetrahedra, corners with two equivalent Se(1)Cu3Ge tetrahedra, corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with three equivalent Se(5)Cu3Ge tetrahedra, and corners with three equivalent Se(6)Cu3Ge tetrahedra. In the fourth Se site, Se(4) is bonded to one Cu(1), one Cu(2), one Ge(1), and one Ge(2) atom to form SeCu2Ge2 tetrahedra that share corners with two equivalent Se(3)Cu2Ge2 tetrahedra, corners with two equivalent Se(5)Cu3Ge tetrahedra, corners with two equivalent Se(6)Cu3Ge tetrahedra, corners with three equivalent Se(1)Cu3Ge tetrahedra, and corners with three equivalent Se(2)Cu3Ge tetrahedra. In the fifth Se site, Se(5) is bonded to one Cu(2), one Cu(3), one Cu(4), and one Ge(2) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(4)Cu2Ge2 tetrahedra, corners with two equivalent Se(1)Cu3Ge tetrahedra, corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with three equivalent Se(3)Cu2Ge2 tetrahedra, and corners with three equivalent Se(6)Cu3Ge tetrahedra. In the sixth Se site, Se(6) is bonded to one Cu(1), one Cu(3), one Cu(4), and one Ge(2) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(4)Cu2Ge2 tetrahedra, corners with two equivalent Se(1)Cu3Ge tetrahedra, corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with three equivalent Se(3)Cu2Ge2 tetrahedra, and corners with three equivalent Se(5)Cu3Ge tetrahedra.
Cu2GeSe3 is Enargite-like structured and crystallizes in the triclinic P1 space group. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Se(1), one Se(2), one Se(4), and one Se(6) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Ge(2)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with three equivalent Ge(1)Se4 tetrahedra. The Cu(1)-Se(1) bond length is 2.39 Å. The Cu(1)-Se(2) bond length is 2.39 Å. The Cu(1)-Se(4) bond length is 2.43 Å. The Cu(1)-Se(6) bond length is 2.40 Å. In the second Cu site, Cu(2) is bonded to one Se(1), one Se(2), one Se(4), and one Se(5) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Ge(2)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Ge(1)Se4 tetrahedra. The Cu(2)-Se(1) bond length is 2.40 Å. The Cu(2)-Se(2) bond length is 2.39 Å. The Cu(2)-Se(4) bond length is 2.41 Å. The Cu(2)-Se(5) bond length is 2.39 Å. In the third Cu site, Cu(3) is bonded to one Se(1), one Se(3), one Se(5), and one Se(6) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(4)Se4 tetrahedra, and corners with three equivalent Ge(2)Se4 tetrahedra. The Cu(3)-Se(1) bond length is 2.40 Å. The Cu(3)-Se(3) bond length is 2.43 Å. The Cu(3)-Se(5) bond length is 2.40 Å. The Cu(3)-Se(6) bond length is 2.39 Å. In the fourth Cu site, Cu(4) is bonded to one Se(2), one Se(3), one Se(5), and one Se(6) atom to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Ge(2)Se4 tetrahedra. The Cu(4)-Se(2) bond length is 2.38 Å. The Cu(4)-Se(3) bond length is 2.42 Å. The Cu(4)-Se(5) bond length is 2.39 Å. The Cu(4)-Se(6) bond length is 2.40 Å. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form GeSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Ge(2)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Cu(2)Se4 tetrahedra. The Ge(1)-Se(1) bond length is 2.37 Å. The Ge(1)-Se(2) bond length is 2.37 Å. The Ge(1)-Se(3) bond length is 2.50 Å. The Ge(1)-Se(4) bond length is 2.48 Å. In the second Ge site, Ge(2) is bonded to one Se(3), one Se(4), one Se(5), and one Se(6) atom to form GeSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Ge(1)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Cu(4)Se4 tetrahedra. The Ge(2)-Se(3) bond length is 2.48 Å. The Ge(2)-Se(4) bond length is 2.50 Å. The Ge(2)-Se(5) bond length is 2.37 Å. The Ge(2)-Se(6) bond length is 2.38 Å. There are six inequivalent Se sites. In the first Se site, Se(1) 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(3)Cu2Ge2 tetrahedra, corners with two equivalent Se(5)Cu3Ge tetrahedra, corners with two equivalent Se(6)Cu3Ge tetrahedra, corners with three equivalent Se(4)Cu2Ge2 tetrahedra, and corners with three equivalent Se(2)Cu3Ge tetrahedra. In the second Se site, Se(2) is bonded to one Cu(1), one Cu(2), one Cu(4), and one Ge(1) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(3)Cu2Ge2 tetrahedra, corners with two equivalent Se(5)Cu3Ge tetrahedra, corners with two equivalent Se(6)Cu3Ge tetrahedra, corners with three equivalent Se(4)Cu2Ge2 tetrahedra, and corners with three equivalent Se(1)Cu3Ge tetrahedra. In the third Se site, Se(3) is bonded to one Cu(3), one Cu(4), one Ge(1), and one Ge(2) atom to form SeCu2Ge2 tetrahedra that share corners with two equivalent Se(4)Cu2Ge2 tetrahedra, corners with two equivalent Se(1)Cu3Ge tetrahedra, corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with three equivalent Se(5)Cu3Ge tetrahedra, and corners with three equivalent Se(6)Cu3Ge tetrahedra. In the fourth Se site, Se(4) is bonded to one Cu(1), one Cu(2), one Ge(1), and one Ge(2) atom to form SeCu2Ge2 tetrahedra that share corners with two equivalent Se(3)Cu2Ge2 tetrahedra, corners with two equivalent Se(5)Cu3Ge tetrahedra, corners with two equivalent Se(6)Cu3Ge tetrahedra, corners with three equivalent Se(1)Cu3Ge tetrahedra, and corners with three equivalent Se(2)Cu3Ge tetrahedra. In the fifth Se site, Se(5) is bonded to one Cu(2), one Cu(3), one Cu(4), and one Ge(2) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(4)Cu2Ge2 tetrahedra, corners with two equivalent Se(1)Cu3Ge tetrahedra, corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with three equivalent Se(3)Cu2Ge2 tetrahedra, and corners with three equivalent Se(6)Cu3Ge tetrahedra. In the sixth Se site, Se(6) is bonded to one Cu(1), one Cu(3), one Cu(4), and one Ge(2) atom to form SeCu3Ge tetrahedra that share corners with two equivalent Se(4)Cu2Ge2 tetrahedra, corners with two equivalent Se(1)Cu3Ge tetrahedra, corners with two equivalent Se(2)Cu3Ge tetrahedra, corners with three equivalent Se(3)Cu2Ge2 tetrahedra, and corners with three equivalent Se(5)Cu3Ge tetrahedra.