Cu2SiTe3 is Enargite-like structured and crystallizes in the monoclinic Cc space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Te(1), one Te(3), and two equivalent Te(2) atoms to form CuTe4 tetrahedra that share corners with two equivalent Cu(1)Te4 tetrahedra, corners with five equivalent Cu(2)Te4 tetrahedra, and corners with five equivalent Si(1)Te4 tetrahedra. In the second Cu site, Cu(2) is bonded to one Te(1), one Te(2), and two equivalent Te(3) atoms to form CuTe4 tetrahedra that share corners with two equivalent Cu(2)Te4 tetrahedra, corners with five equivalent Cu(1)Te4 tetrahedra, and corners with five equivalent Si(1)Te4 tetrahedra. Si(1) is bonded to one Te(2), one Te(3), and two equivalent Te(1) atoms to form SiTe4 tetrahedra that share corners with two equivalent Si(1)Te4 tetrahedra, corners with five equivalent Cu(1)Te4 tetrahedra, and corners with five equivalent Cu(2)Te4 tetrahedra. There are three inequivalent Te sites. In the first Te site, Te(1) is bonded to one Cu(1), one Cu(2), and two equivalent Si(1) atoms to form TeCu2Si2 tetrahedra that share corners with two equivalent Te(1)Cu2Si2 tetrahedra, corners with five equivalent Te(2)Cu3Si tetrahedra, and corners with five equivalent Te(3)Cu3Si tetrahedra. In the second Te site, Te(2) is bonded to one Cu(2), two equivalent Cu(1), and one Si(1) atom to form TeCu3Si tetrahedra that share corners with two equivalent Te(2)Cu3Si tetrahedra, corners with five equivalent Te(1)Cu2Si2 tetrahedra, and corners with five equivalent Te(3)Cu3Si tetrahedra. In the third Te site, Te(3) is bonded to one Cu(1), two equivalent Cu(2), and one Si(1) atom to form TeCu3Si tetrahedra that share corners with two equivalent Te(3)Cu3Si tetrahedra, corners with five equivalent Te(1)Cu2Si2 tetrahedra, and corners with five equivalent Te(2)Cu3Si tetrahedra.
Cu2SiTe3 is Enargite-like structured and crystallizes in the monoclinic Cc space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Te(1), one Te(3), and two equivalent Te(2) atoms to form CuTe4 tetrahedra that share corners with two equivalent Cu(1)Te4 tetrahedra, corners with five equivalent Cu(2)Te4 tetrahedra, and corners with five equivalent Si(1)Te4 tetrahedra. The Cu(1)-Te(1) bond length is 2.60 Å. The Cu(1)-Te(3) bond length is 2.56 Å. There is one shorter (2.55 Å) and one longer (2.56 Å) Cu(1)-Te(2) bond length. In the second Cu site, Cu(2) is bonded to one Te(1), one Te(2), and two equivalent Te(3) atoms to form CuTe4 tetrahedra that share corners with two equivalent Cu(2)Te4 tetrahedra, corners with five equivalent Cu(1)Te4 tetrahedra, and corners with five equivalent Si(1)Te4 tetrahedra. The Cu(2)-Te(1) bond length is 2.58 Å. The Cu(2)-Te(2) bond length is 2.55 Å. Both Cu(2)-Te(3) bond lengths are 2.55 Å. Si(1) is bonded to one Te(2), one Te(3), and two equivalent Te(1) atoms to form SiTe4 tetrahedra that share corners with two equivalent Si(1)Te4 tetrahedra, corners with five equivalent Cu(1)Te4 tetrahedra, and corners with five equivalent Cu(2)Te4 tetrahedra. The Si(1)-Te(2) bond length is 2.52 Å. The Si(1)-Te(3) bond length is 2.52 Å. There is one shorter (2.61 Å) and one longer (2.64 Å) Si(1)-Te(1) bond length. There are three inequivalent Te sites. In the first Te site, Te(1) is bonded to one Cu(1), one Cu(2), and two equivalent Si(1) atoms to form TeCu2Si2 tetrahedra that share corners with two equivalent Te(1)Cu2Si2 tetrahedra, corners with five equivalent Te(2)Cu3Si tetrahedra, and corners with five equivalent Te(3)Cu3Si tetrahedra. In the second Te site, Te(2) is bonded to one Cu(2), two equivalent Cu(1), and one Si(1) atom to form TeCu3Si tetrahedra that share corners with two equivalent Te(2)Cu3Si tetrahedra, corners with five equivalent Te(1)Cu2Si2 tetrahedra, and corners with five equivalent Te(3)Cu3Si tetrahedra. In the third Te site, Te(3) is bonded to one Cu(1), two equivalent Cu(2), and one Si(1) atom to form TeCu3Si tetrahedra that share corners with two equivalent Te(3)Cu3Si tetrahedra, corners with five equivalent Te(1)Cu2Si2 tetrahedra, and corners with five equivalent Te(2)Cu3Si tetrahedra.