K4SnSe4 crystallizes in the orthorhombic Pnma space group. There are three inequivalent K sites. In the first K site, K(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form distorted KSe6 octahedra that share corners with two equivalent Sn(1)K2Se4 tetrahedra, edges with two equivalent K(1)Se6 octahedra, and edges with two equivalent Sn(1)K2Se4 tetrahedra. In the second K site, K(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(3), and four equivalent Se(2) atoms. In the third K site, K(3) is bonded in a 7-coordinate geometry to one Sn(1), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. Sn(1) is bonded to two equivalent K(3), one Se(1), one Se(3), and two equivalent Se(2) atoms to form SnK2Se4 tetrahedra that share corners with two equivalent K(1)Se6 octahedra, corners with four equivalent Se(2)K5Sn octahedra, and edges with two equivalent K(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 43-138°. There are three inequivalent Se sites. In the first Se site, Se(3) is bonded in a 8-coordinate geometry to one K(2), two equivalent K(1), four equivalent K(3), and one Sn(1) atom. In the second Se site, Se(1) is bonded in a 8-coordinate geometry to one K(2), two equivalent K(1), four equivalent K(3), and one Sn(1) atom. In the third Se site, Se(2) is bonded to one K(1), two equivalent K(2), two equivalent K(3), and one Sn(1) atom to form distorted SeK5Sn octahedra that share corners with six equivalent Se(2)K5Sn octahedra, corners with two equivalent Sn(1)K2Se4 tetrahedra, and edges with two equivalent Se(2)K5Sn octahedra. The corner-sharing octahedral tilt angles range from 0-46°.
K4SnSe4 crystallizes in the orthorhombic Pnma space group. There are three inequivalent K sites. In the first K site, K(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form distorted KSe6 octahedra that share corners with two equivalent Sn(1)K2Se4 tetrahedra, edges with two equivalent K(1)Se6 octahedra, and edges with two equivalent Sn(1)K2Se4 tetrahedra. Both K(1)-Se(1) bond lengths are 3.66 Å. Both K(1)-Se(2) bond lengths are 3.27 Å. Both K(1)-Se(3) bond lengths are 3.78 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to one Se(1), one Se(3), and four equivalent Se(2) atoms. The K(2)-Se(1) bond length is 3.71 Å. The K(2)-Se(3) bond length is 3.37 Å. There are two shorter (3.34 Å) and two longer (3.36 Å) K(2)-Se(2) bond lengths. In the third K site, K(3) is bonded in a 7-coordinate geometry to one Sn(1), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. The K(3)-Sn(1) bond length is 3.56 Å. There is one shorter (3.34 Å) and one longer (3.80 Å) K(3)-Se(1) bond length. There is one shorter (3.29 Å) and one longer (3.38 Å) K(3)-Se(2) bond length. There is one shorter (3.44 Å) and one longer (3.68 Å) K(3)-Se(3) bond length. Sn(1) is bonded to two equivalent K(3), one Se(1), one Se(3), and two equivalent Se(2) atoms to form SnK2Se4 tetrahedra that share corners with two equivalent K(1)Se6 octahedra, corners with four equivalent Se(2)K5Sn octahedra, and edges with two equivalent K(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 43-138°. The Sn(1)-Se(1) bond length is 2.55 Å. The Sn(1)-Se(3) bond length is 2.56 Å. Both Sn(1)-Se(2) bond lengths are 2.52 Å. There are three inequivalent Se sites. In the first Se site, Se(3) is bonded in a 8-coordinate geometry to one K(2), two equivalent K(1), four equivalent K(3), and one Sn(1) atom. In the second Se site, Se(1) is bonded in a 8-coordinate geometry to one K(2), two equivalent K(1), four equivalent K(3), and one Sn(1) atom. In the third Se site, Se(2) is bonded to one K(1), two equivalent K(2), two equivalent K(3), and one Sn(1) atom to form distorted SeK5Sn octahedra that share corners with six equivalent Se(2)K5Sn octahedra, corners with two equivalent Sn(1)K2Se4 tetrahedra, and edges with two equivalent Se(2)K5Sn octahedra. The corner-sharing octahedral tilt angles range from 0-46°.