Cu5Sn2Se7 is Enargite-like structured and crystallizes in the monoclinic C2 space group. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(2)Se4 tetrahedra, corners with four equivalent Sn(1)Se4 tetrahedra, and corners with six equivalent Cu(3)Se4 tetrahedra. In the second Cu site, Cu(2) is bonded to one Se(2), one Se(3), and two equivalent Se(4) atoms to form CuSe4 tetrahedra that share  a cornercorner with one Cu(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with five equivalent Sn(1)Se4 tetrahedra. In the third Cu site, Cu(3) is bonded to one Se(3), one Se(4), and two equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with four equivalent Sn(1)Se4 tetrahedra. 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  a cornercorner with one Sn(1)Se4 tetrahedra, corners with two equivalent Cu(1)Se4 tetrahedra, corners with four equivalent Cu(3)Se4 tetrahedra, and corners with five equivalent Cu(2)Se4 tetrahedra. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cu(1), two equivalent Cu(3), and one Sn(1) atom to form SeCu3Sn tetrahedra that share  a cornercorner with one Se(2)Cu2Sn2 tetrahedra, corners with three equivalent Se(1)Cu3Sn tetrahedra, corners with three equivalent Se(4)Cu3Sn tetrahedra, and corners with five equivalent Se(3)Cu3Sn tetrahedra. In the second Se site, Se(2) is bonded to two equivalent Cu(2) and two equivalent Sn(1) atoms to form corner-sharing SeCu2Sn2 tetrahedra. In the third Se site, Se(3) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Sn(1) atom to form SeCu3Sn tetrahedra that share  a cornercorner with one Se(3)Cu3Sn tetrahedra, corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with four equivalent Se(4)Cu3Sn tetrahedra, and corners with five equivalent Se(1)Cu3Sn tetrahedra. In the fourth Se site, Se(4) is bonded to one Cu(3), two equivalent Cu(2), and one Sn(1) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(2)Cu2Sn2 tetrahedra, corners with three equivalent Se(1)Cu3Sn tetrahedra, and corners with four equivalent Se(3)Cu3Sn tetrahedra.
Cu5Sn2Se7 is Enargite-like structured and crystallizes in the monoclinic C2 space group. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(3) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(2)Se4 tetrahedra, corners with four equivalent Sn(1)Se4 tetrahedra, and corners with six equivalent Cu(3)Se4 tetrahedra. Both Cu(1)-Se(1) bond lengths are 2.40 Å. Both Cu(1)-Se(3) bond lengths are 2.41 Å. In the second Cu site, Cu(2) is bonded to one Se(2), one Se(3), and two equivalent Se(4) atoms to form CuSe4 tetrahedra that share  a cornercorner with one Cu(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, corners with three equivalent Cu(3)Se4 tetrahedra, and corners with five equivalent Sn(1)Se4 tetrahedra. The Cu(2)-Se(2) bond length is 2.43 Å. The Cu(2)-Se(3) bond length is 2.38 Å. There is one shorter (2.39 Å) and one longer (2.40 Å) Cu(2)-Se(4) bond length. In the third Cu site, Cu(3) is bonded to one Se(3), one Se(4), and two equivalent Se(1) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(3)Se4 tetrahedra, corners with three equivalent Cu(1)Se4 tetrahedra, corners with three equivalent Cu(2)Se4 tetrahedra, and corners with four equivalent Sn(1)Se4 tetrahedra. The Cu(3)-Se(3) bond length is 2.39 Å. The Cu(3)-Se(4) bond length is 2.40 Å. There is one shorter (2.40 Å) and one longer (2.41 Å) Cu(3)-Se(1) bond length. 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  a cornercorner with one Sn(1)Se4 tetrahedra, corners with two equivalent Cu(1)Se4 tetrahedra, corners with four equivalent Cu(3)Se4 tetrahedra, and corners with five equivalent Cu(2)Se4 tetrahedra. The Sn(1)-Se(1) bond length is 2.57 Å. The Sn(1)-Se(2) bond length is 2.66 Å. The Sn(1)-Se(3) bond length is 2.57 Å. The Sn(1)-Se(4) bond length is 2.57 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cu(1), two equivalent Cu(3), and one Sn(1) atom to form SeCu3Sn tetrahedra that share  a cornercorner with one Se(2)Cu2Sn2 tetrahedra, corners with three equivalent Se(1)Cu3Sn tetrahedra, corners with three equivalent Se(4)Cu3Sn tetrahedra, and corners with five equivalent Se(3)Cu3Sn tetrahedra. In the second Se site, Se(2) is bonded to two equivalent Cu(2) and two equivalent Sn(1) atoms to form corner-sharing SeCu2Sn2 tetrahedra. In the third Se site, Se(3) is bonded to one Cu(1), one Cu(2), one Cu(3), and one Sn(1) atom to form SeCu3Sn tetrahedra that share  a cornercorner with one Se(3)Cu3Sn tetrahedra, corners with two equivalent Se(2)Cu2Sn2 tetrahedra, corners with four equivalent Se(4)Cu3Sn tetrahedra, and corners with five equivalent Se(1)Cu3Sn tetrahedra. In the fourth Se site, Se(4) is bonded to one Cu(3), two equivalent Cu(2), and one Sn(1) atom to form SeCu3Sn tetrahedra that share corners with two equivalent Se(4)Cu3Sn tetrahedra, corners with three equivalent Se(2)Cu2Sn2 tetrahedra, corners with three equivalent Se(1)Cu3Sn tetrahedra, and corners with four equivalent Se(3)Cu3Sn tetrahedra.