Cd4SiSe6 crystallizes in the monoclinic Cc space group. There are four inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to one Se(1), one Se(2), one Se(5), and one Se(6) atom to form CdSe4 trigonal pyramids that share corners with two equivalent Cd(4)Se4 tetrahedra, corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(2)Se4 tetrahedra, and corners with three equivalent Cd(3)Se4 tetrahedra. In the second Cd site, Cd(2) is bonded to one Se(1), one Se(2), one Se(4), and one Se(5) atom to form CdSe4 tetrahedra that share corners with two equivalent Cd(3)Se4 tetrahedra, corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(4)Se4 tetrahedra, and corners with three equivalent Cd(1)Se4 trigonal pyramids. In the third Cd site, Cd(3) is bonded to one Se(1), one Se(3), one Se(5), and one Se(6) atom to form CdSe4 tetrahedra that share corners with two equivalent Cd(2)Se4 tetrahedra, corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(4)Se4 tetrahedra, and corners with three equivalent Cd(1)Se4 trigonal pyramids. In the fourth Cd site, Cd(4) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form CdSe4 tetrahedra that share corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(2)Se4 tetrahedra, corners with three equivalent Cd(3)Se4 tetrahedra, and corners with two equivalent Cd(1)Se4 trigonal pyramids. Si(1) is bonded to one Se(2), one Se(3), one Se(4), and one Se(6) atom to form SiSe4 tetrahedra that share corners with two equivalent Cd(2)Se4 tetrahedra, corners with two equivalent Cd(3)Se4 tetrahedra, corners with two equivalent Cd(4)Se4 tetrahedra, and corners with two equivalent Cd(1)Se4 trigonal pyramids. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cd(1), one Cd(2), one Cd(3), and one Cd(4) atom to form corner-sharing SeCd4 trigonal pyramids. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one Cd(1), one Cd(2), and one Si(1) atom. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one Cd(3), one Cd(4), and one Si(1) atom. In the fourth Se site, Se(4) is bonded in a trigonal non-coplanar geometry to one Cd(2), one Cd(4), and one Si(1) atom. In the fifth Se site, Se(5) is bonded to one Cd(1), one Cd(2), one Cd(3), and one Cd(4) atom to form corner-sharing SeCd4 tetrahedra. In the sixth Se site, Se(6) is bonded in a distorted trigonal non-coplanar geometry to one Cd(1), one Cd(3), and one Si(1) atom.
Cd4SiSe6 crystallizes in the monoclinic Cc space group. There are four inequivalent Cd sites. In the first Cd site, Cd(1) is bonded to one Se(1), one Se(2), one Se(5), and one Se(6) atom to form CdSe4 trigonal pyramids that share corners with two equivalent Cd(4)Se4 tetrahedra, corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(2)Se4 tetrahedra, and corners with three equivalent Cd(3)Se4 tetrahedra. The Cd(1)-Se(1) bond length is 2.72 Å. The Cd(1)-Se(2) bond length is 2.82 Å. The Cd(1)-Se(5) bond length is 2.70 Å. The Cd(1)-Se(6) bond length is 2.72 Å. In the second Cd site, Cd(2) is bonded to one Se(1), one Se(2), one Se(4), and one Se(5) atom to form CdSe4 tetrahedra that share corners with two equivalent Cd(3)Se4 tetrahedra, corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(4)Se4 tetrahedra, and corners with three equivalent Cd(1)Se4 trigonal pyramids. The Cd(2)-Se(1) bond length is 2.68 Å. The Cd(2)-Se(2) bond length is 2.73 Å. The Cd(2)-Se(4) bond length is 2.71 Å. The Cd(2)-Se(5) bond length is 2.72 Å. In the third Cd site, Cd(3) is bonded to one Se(1), one Se(3), one Se(5), and one Se(6) atom to form CdSe4 tetrahedra that share corners with two equivalent Cd(2)Se4 tetrahedra, corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(4)Se4 tetrahedra, and corners with three equivalent Cd(1)Se4 trigonal pyramids. The Cd(3)-Se(1) bond length is 2.68 Å. The Cd(3)-Se(3) bond length is 2.76 Å. The Cd(3)-Se(5) bond length is 2.70 Å. The Cd(3)-Se(6) bond length is 2.71 Å. In the fourth Cd site, Cd(4) is bonded to one Se(1), one Se(3), one Se(4), and one Se(5) atom to form CdSe4 tetrahedra that share corners with two equivalent Si(1)Se4 tetrahedra, corners with three equivalent Cd(2)Se4 tetrahedra, corners with three equivalent Cd(3)Se4 tetrahedra, and corners with two equivalent Cd(1)Se4 trigonal pyramids. The Cd(4)-Se(1) bond length is 2.73 Å. The Cd(4)-Se(3) bond length is 2.73 Å. The Cd(4)-Se(4) bond length is 2.77 Å. The Cd(4)-Se(5) bond length is 2.69 Å. Si(1) is bonded to one Se(2), one Se(3), one Se(4), and one Se(6) atom to form SiSe4 tetrahedra that share corners with two equivalent Cd(2)Se4 tetrahedra, corners with two equivalent Cd(3)Se4 tetrahedra, corners with two equivalent Cd(4)Se4 tetrahedra, and corners with two equivalent Cd(1)Se4 trigonal pyramids. The Si(1)-Se(2) bond length is 2.28 Å. The Si(1)-Se(3) bond length is 2.29 Å. The Si(1)-Se(4) bond length is 2.29 Å. The Si(1)-Se(6) bond length is 2.30 Å. There are six inequivalent Se sites. In the first Se site, Se(1) is bonded to one Cd(1), one Cd(2), one Cd(3), and one Cd(4) atom to form corner-sharing SeCd4 trigonal pyramids. In the second Se site, Se(2) is bonded in a trigonal non-coplanar geometry to one Cd(1), one Cd(2), and one Si(1) atom. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one Cd(3), one Cd(4), and one Si(1) atom. In the fourth Se site, Se(4) is bonded in a trigonal non-coplanar geometry to one Cd(2), one Cd(4), and one Si(1) atom. In the fifth Se site, Se(5) is bonded to one Cd(1), one Cd(2), one Cd(3), and one Cd(4) atom to form corner-sharing SeCd4 tetrahedra. In the sixth Se site, Se(6) is bonded in a distorted trigonal non-coplanar geometry to one Cd(1), one Cd(3), and one Si(1) atom.