K2WSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and four equivalent Se(3) atoms. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and four equivalent Se(3) atoms. W(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), and two equivalent Se(3) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1), two equivalent K(2), and one W(1) atom to form distorted SeK4W trigonal bipyramids that share  a cornercorner with one Se(2)K5W octahedra, corners with four equivalent Se(1)K4W trigonal bipyramids, corners with six equivalent Se(3)K4W trigonal bipyramids, edges with five equivalent Se(2)K5W octahedra, and edges with six equivalent Se(3)K4W trigonal bipyramids. The corner-sharing octahedral tilt angles are 19°. In the second Se site, Se(2) is bonded to two equivalent K(2), three equivalent K(1), and one W(1) atom to form distorted SeK5W octahedra that share corners with four equivalent Se(2)K5W octahedra,  a cornercorner with one Se(1)K4W trigonal bipyramid, corners with ten equivalent Se(3)K4W trigonal bipyramids, edges with two equivalent Se(2)K5W octahedra, edges with five equivalent Se(1)K4W trigonal bipyramids, and edges with six equivalent Se(3)K4W trigonal bipyramids. The corner-sharing octahedral tilt angles range from 21-68°. In the third Se site, Se(3) is bonded to two equivalent K(1), two equivalent K(2), and one W(1) atom to form distorted SeK4W trigonal bipyramids that share corners with five equivalent Se(2)K5W octahedra, corners with three equivalent Se(1)K4W trigonal bipyramids, corners with six equivalent Se(3)K4W trigonal bipyramids, edges with three equivalent Se(2)K5W octahedra, edges with two equivalent Se(3)K4W trigonal bipyramids, edges with three equivalent Se(1)K4W trigonal bipyramids, and  a faceface with one Se(3)K4W trigonal bipyramid. The corner-sharing octahedral tilt angles range from 32-58°.
K2WSe4 crystallizes in the orthorhombic Pnma space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to two equivalent Se(1), three equivalent Se(2), and four equivalent Se(3) atoms. There is one shorter (3.28 Å) and one longer (3.36 Å) K(1)-Se(1) bond length. There is one shorter (3.46 Å) and two longer (3.66 Å) K(1)-Se(2) bond lengths. There are two shorter (3.47 Å) and two longer (3.69 Å) K(1)-Se(3) bond lengths. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and four equivalent Se(3) atoms. Both K(2)-Se(1) bond lengths are 3.66 Å. There is one shorter (3.56 Å) and one longer (3.74 Å) K(2)-Se(2) bond length. There are two shorter (3.52 Å) and two longer (3.63 Å) K(2)-Se(3) bond lengths. W(1) is bonded in a tetrahedral geometry to one Se(1), one Se(2), and two equivalent Se(3) atoms. The W(1)-Se(1) bond length is 2.32 Å. The W(1)-Se(2) bond length is 2.34 Å. Both W(1)-Se(3) bond lengths are 2.31 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent K(1), two equivalent K(2), and one W(1) atom to form distorted SeK4W trigonal bipyramids that share  a cornercorner with one Se(2)K5W octahedra, corners with four equivalent Se(1)K4W trigonal bipyramids, corners with six equivalent Se(3)K4W trigonal bipyramids, edges with five equivalent Se(2)K5W octahedra, and edges with six equivalent Se(3)K4W trigonal bipyramids. The corner-sharing octahedral tilt angles are 19°. In the second Se site, Se(2) is bonded to two equivalent K(2), three equivalent K(1), and one W(1) atom to form distorted SeK5W octahedra that share corners with four equivalent Se(2)K5W octahedra,  a cornercorner with one Se(1)K4W trigonal bipyramid, corners with ten equivalent Se(3)K4W trigonal bipyramids, edges with two equivalent Se(2)K5W octahedra, edges with five equivalent Se(1)K4W trigonal bipyramids, and edges with six equivalent Se(3)K4W trigonal bipyramids. The corner-sharing octahedral tilt angles range from 21-68°. In the third Se site, Se(3) is bonded to two equivalent K(1), two equivalent K(2), and one W(1) atom to form distorted SeK4W trigonal bipyramids that share corners with five equivalent Se(2)K5W octahedra, corners with three equivalent Se(1)K4W trigonal bipyramids, corners with six equivalent Se(3)K4W trigonal bipyramids, edges with three equivalent Se(2)K5W octahedra, edges with two equivalent Se(3)K4W trigonal bipyramids, edges with three equivalent Se(1)K4W trigonal bipyramids, and  a faceface with one Se(3)K4W trigonal bipyramid. The corner-sharing octahedral tilt angles range from 32-58°.