Cu2SnSe3 is Enargite-like structured and crystallizes in the monoclinic Cc space group. There are four inequivalent Cu sites. In the first Cu site, Cu(1) 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(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Sn(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with three equivalent Sn(2)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to one Se(3), one Se(4), one Se(5), 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 Sn(1)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Sn(2)Se4 tetrahedra. In the third Cu site, Cu(3) 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(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Sn(2)Se4 tetrahedra, corners with three equivalent Cu(4)Se4 tetrahedra, and corners with three equivalent Sn(1)Se4 tetrahedra. In the fourth Cu site, Cu(4) 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(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Sn(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Sn(1)Se4 tetrahedra. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form SnSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Sn(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Cu(4)Se4 tetrahedra. In the second Sn site, Sn(2) is bonded to one Se(2), one Se(3), one Se(5), and one Se(6) atom to form SnSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Sn(1)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Cu(2)Se4 tetrahedra. There are six inequivalent Se sites. In the first Se site, Se(5) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Sn(2) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with two equivalent Se(1)Cu3Sn tetrahedra, corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(3)Cu2Sn2 tetrahedra, and corners with three equivalent Se(6)Cu3Sn tetrahedra. In the second Se site, Se(6) is bonded to one Cu(1), one Cu(2), one Cu(4), and one Sn(2) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with two equivalent Se(1)Cu3Sn tetrahedra, corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(3)Cu2Sn2 tetrahedra, and corners with three equivalent Se(5)Cu3Sn tetrahedra. In the third Se site, Se(1) is bonded to one Cu(1), one Cu(3), one Cu(4), and one Sn(1) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(3)Cu2Sn2 tetrahedra, corners with two equivalent Se(5)Cu3Sn tetrahedra, corners with two equivalent Se(6)Cu3Sn tetrahedra, corners with three equivalent Se(2)Cu2Sn2 tetrahedra, and corners with three equivalent Se(4)Cu3Sn tetrahedra. In the fourth Se site, Se(2) is bonded to one Cu(3), one Cu(4), one Sn(1), and one Sn(2) atom to form SeCu2Sn2 tetrahedra that share corners with two equivalent Se(3)Cu2Sn2 tetrahedra, corners with two equivalent Se(5)Cu3Sn tetrahedra, corners with two equivalent Se(6)Cu3Sn tetrahedra, corners with three equivalent Se(1)Cu3Sn tetrahedra, and corners with three equivalent Se(4)Cu3Sn tetrahedra. In the fifth Se site, Se(3) is bonded to one Cu(1), one Cu(2), one Sn(1), and one Sn(2) atom to form SeCu2Sn2 tetrahedra that share corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with two equivalent Se(1)Cu3Sn tetrahedra, corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(5)Cu3Sn tetrahedra, and corners with three equivalent Se(6)Cu3Sn tetrahedra. In the sixth Se site, Se(4) is bonded to one Cu(2), one Cu(3), one Cu(4), and one Sn(1) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(3)Cu2Sn2 tetrahedra, corners with two equivalent Se(5)Cu3Sn tetrahedra, corners with two equivalent Se(6)Cu3Sn tetrahedra, corners with three equivalent Se(2)Cu2Sn2 tetrahedra, and corners with three equivalent Se(1)Cu3Sn tetrahedra.
Cu2SnSe3 is Enargite-like structured and crystallizes in the monoclinic Cc space group. There are four inequivalent Cu sites. In the first Cu site, Cu(1) 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(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Sn(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with three equivalent Sn(2)Se4 tetrahedra. The Cu(1)-Se(1) bond length is 2.41 Å. The Cu(1)-Se(3) bond length is 2.44 Å. The Cu(1)-Se(5) bond length is 2.42 Å. The Cu(1)-Se(6) bond length is 2.43 Å. In the second Cu site, Cu(2) is bonded to one Se(3), one Se(4), one Se(5), 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 Sn(1)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Sn(2)Se4 tetrahedra. The Cu(2)-Se(3) bond length is 2.46 Å. The Cu(2)-Se(4) bond length is 2.43 Å. The Cu(2)-Se(5) bond length is 2.43 Å. The Cu(2)-Se(6) bond length is 2.41 Å. In the third Cu site, Cu(3) 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(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Sn(2)Se4 tetrahedra, corners with three equivalent Cu(4)Se4 tetrahedra, and corners with three equivalent Sn(1)Se4 tetrahedra. The Cu(3)-Se(1) bond length is 2.41 Å. The Cu(3)-Se(2) bond length is 2.46 Å. The Cu(3)-Se(4) bond length is 2.43 Å. The Cu(3)-Se(5) bond length is 2.42 Å. In the fourth Cu site, Cu(4) 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(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Sn(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Sn(1)Se4 tetrahedra. The Cu(4)-Se(1) bond length is 2.43 Å. The Cu(4)-Se(2) bond length is 2.45 Å. The Cu(4)-Se(4) bond length is 2.42 Å. The Cu(4)-Se(6) bond length is 2.42 Å. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form SnSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(2)Se4 tetrahedra, corners with two equivalent Sn(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with three equivalent Cu(4)Se4 tetrahedra. The Sn(1)-Se(1) bond length is 2.60 Å. The Sn(1)-Se(2) bond length is 2.69 Å. The Sn(1)-Se(3) bond length is 2.68 Å. The Sn(1)-Se(4) bond length is 2.60 Å. In the second Sn site, Sn(2) is bonded to one Se(2), one Se(3), one Se(5), and one Se(6) atom to form SnSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra, corners with two equivalent Sn(1)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, and corners with three equivalent Cu(2)Se4 tetrahedra. The Sn(2)-Se(2) bond length is 2.68 Å. The Sn(2)-Se(3) bond length is 2.70 Å. The Sn(2)-Se(5) bond length is 2.60 Å. The Sn(2)-Se(6) bond length is 2.60 Å. There are six inequivalent Se sites. In the first Se site, Se(5) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Sn(2) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with two equivalent Se(1)Cu3Sn tetrahedra, corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(3)Cu2Sn2 tetrahedra, and corners with three equivalent Se(6)Cu3Sn tetrahedra. In the second Se site, Se(6) is bonded to one Cu(1), one Cu(2), one Cu(4), and one Sn(2) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with two equivalent Se(1)Cu3Sn tetrahedra, corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(3)Cu2Sn2 tetrahedra, and corners with three equivalent Se(5)Cu3Sn tetrahedra. In the third Se site, Se(1) is bonded to one Cu(1), one Cu(3), one Cu(4), and one Sn(1) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(3)Cu2Sn2 tetrahedra, corners with two equivalent Se(5)Cu3Sn tetrahedra, corners with two equivalent Se(6)Cu3Sn tetrahedra, corners with three equivalent Se(2)Cu2Sn2 tetrahedra, and corners with three equivalent Se(4)Cu3Sn tetrahedra. In the fourth Se site, Se(2) is bonded to one Cu(3), one Cu(4), one Sn(1), and one Sn(2) atom to form SeCu2Sn2 tetrahedra that share corners with two equivalent Se(3)Cu2Sn2 tetrahedra, corners with two equivalent Se(5)Cu3Sn tetrahedra, corners with two equivalent Se(6)Cu3Sn tetrahedra, corners with three equivalent Se(1)Cu3Sn tetrahedra, and corners with three equivalent Se(4)Cu3Sn tetrahedra. In the fifth Se site, Se(3) is bonded to one Cu(1), one Cu(2), one Sn(1), and one Sn(2) atom to form SeCu2Sn2 tetrahedra that share corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with two equivalent Se(1)Cu3Sn tetrahedra, corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(5)Cu3Sn tetrahedra, and corners with three equivalent Se(6)Cu3Sn tetrahedra. In the sixth Se site, Se(4) is bonded to one Cu(2), one Cu(3), one Cu(4), and one Sn(1) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(3)Cu2Sn2 tetrahedra, corners with two equivalent Se(5)Cu3Sn tetrahedra, corners with two equivalent Se(6)Cu3Sn tetrahedra, corners with three equivalent Se(2)Cu2Sn2 tetrahedra, and corners with three equivalent Se(1)Cu3Sn tetrahedra.