HgCr2S4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one S(2), one S(3), and four equivalent S(1) atoms to form edge-sharing CrS6 octahedra. In the second Cr site, Cr(2) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form edge-sharing CrS6 octahedra. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 6-coordinate geometry to two equivalent S(2) and four equivalent S(1) atoms. In the second Hg site, Hg(2) is bonded in a 6-coordinate geometry to two equivalent S(3) and four equivalent S(1) atoms. There are three inequivalent S sites. In the first S site, S(1) is bonded to one Cr(2), two equivalent Cr(1), one Hg(1), and one Hg(2) atom to form distorted SCr3Hg2 trigonal bipyramids that share corners with five equivalent S(1)Cr3Hg2 trigonal bipyramids, corners with two equivalent S(3)Cr3Hg trigonal pyramids, edges with four equivalent S(1)Cr3Hg2 trigonal bipyramids, and edges with two equivalent S(3)Cr3Hg trigonal pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Hg(1) atom. In the third S site, S(3) is bonded to one Cr(1), two equivalent Cr(2), and one Hg(2) atom to form SCr3Hg trigonal pyramids that share corners with four equivalent S(1)Cr3Hg2 trigonal bipyramids, corners with three equivalent S(3)Cr3Hg trigonal pyramids, and edges with four equivalent S(1)Cr3Hg2 trigonal bipyramids.
HgCr2S4 crystallizes in the orthorhombic Pmmn space group. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one S(2), one S(3), and four equivalent S(1) atoms to form edge-sharing CrS6 octahedra. The Cr(1)-S(2) bond length is 2.41 Å. The Cr(1)-S(3) bond length is 2.40 Å. There are two shorter (2.38 Å) and two longer (2.48 Å) Cr(1)-S(1) bond lengths. In the second Cr site, Cr(2) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form edge-sharing CrS6 octahedra. Both Cr(2)-S(1) bond lengths are 2.43 Å. Both Cr(2)-S(2) bond lengths are 2.37 Å. Both Cr(2)-S(3) bond lengths are 2.40 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 6-coordinate geometry to two equivalent S(2) and four equivalent S(1) atoms. Both Hg(1)-S(2) bond lengths are 2.67 Å. All Hg(1)-S(1) bond lengths are 2.95 Å. In the second Hg site, Hg(2) is bonded in a 6-coordinate geometry to two equivalent S(3) and four equivalent S(1) atoms. Both Hg(2)-S(3) bond lengths are 2.68 Å. All Hg(2)-S(1) bond lengths are 2.98 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to one Cr(2), two equivalent Cr(1), one Hg(1), and one Hg(2) atom to form distorted SCr3Hg2 trigonal bipyramids that share corners with five equivalent S(1)Cr3Hg2 trigonal bipyramids, corners with two equivalent S(3)Cr3Hg trigonal pyramids, edges with four equivalent S(1)Cr3Hg2 trigonal bipyramids, and edges with two equivalent S(3)Cr3Hg trigonal pyramids. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Hg(1) atom. In the third S site, S(3) is bonded to one Cr(1), two equivalent Cr(2), and one Hg(2) atom to form SCr3Hg trigonal pyramids that share corners with four equivalent S(1)Cr3Hg2 trigonal bipyramids, corners with three equivalent S(3)Cr3Hg trigonal pyramids, and edges with four equivalent S(1)Cr3Hg2 trigonal bipyramids.