Mg2Cr3NiS8 is Spinel-derived structured and crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to one S(1), one S(2), and two equivalent S(3) atoms to form MgS4 tetrahedra that share corners with three equivalent Cr(1)S6 octahedra, corners with three equivalent Ni(1)S6 octahedra, and corners with six equivalent Cr(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 58-61°. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent S(1) and four equivalent S(3) atoms to form CrS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(1)S6 octahedra, and edges with four equivalent Cr(2)S6 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 CrS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Cr(1)S6 octahedra, edges with two equivalent Cr(2)S6 octahedra, and edges with two equivalent Ni(1)S6 octahedra. Ni(1) is bonded to two equivalent S(2) and four equivalent S(3) atoms to form NiS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Cr(1)S6 octahedra, and edges with four equivalent Cr(2)S6 octahedra. There are three inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one Cr(1), and two equivalent Cr(2) atoms to form distorted SMgCr3 trigonal pyramids that share corners with three equivalent S(2)MgCr2Ni tetrahedra, corners with six equivalent S(3)MgCr2Ni tetrahedra, corners with three equivalent S(1)MgCr3 trigonal pyramids,  an edgeedge with one S(2)MgCr2Ni tetrahedra, and edges with two equivalent S(3)MgCr2Ni tetrahedra. In the second S site, S(2) is bonded to one Mg(1), two equivalent Cr(2), and one Ni(1) atom to form distorted SMgCr2Ni tetrahedra that share corners with three equivalent S(2)MgCr2Ni tetrahedra, corners with six equivalent S(3)MgCr2Ni tetrahedra, corners with three equivalent S(1)MgCr3 trigonal pyramids, edges with two equivalent S(3)MgCr2Ni tetrahedra, and  an edgeedge with one S(1)MgCr3 trigonal pyramid. In the third S site, S(3) is bonded to one Mg(1), one Cr(1), one Cr(2), and one Ni(1) atom to form distorted SMgCr2Ni tetrahedra that share corners with three equivalent S(2)MgCr2Ni tetrahedra, corners with six equivalent S(3)MgCr2Ni tetrahedra, corners with three equivalent S(1)MgCr3 trigonal pyramids,  an edgeedge with one S(2)MgCr2Ni tetrahedra,  an edgeedge with one S(3)MgCr2Ni tetrahedra, and  an edgeedge with one S(1)MgCr3 trigonal pyramid.
Mg2Cr3NiS8 is Spinel-derived structured and crystallizes in the monoclinic C2/m space group. Mg(1) is bonded to one S(1), one S(2), and two equivalent S(3) atoms to form MgS4 tetrahedra that share corners with three equivalent Cr(1)S6 octahedra, corners with three equivalent Ni(1)S6 octahedra, and corners with six equivalent Cr(2)S6 octahedra. The corner-sharing octahedral tilt angles range from 58-61°. The Mg(1)-S(1) bond length is 2.43 Å. The Mg(1)-S(2) bond length is 2.45 Å. Both Mg(1)-S(3) bond lengths are 2.45 Å. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent S(1) and four equivalent S(3) atoms to form CrS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(1)S6 octahedra, and edges with four equivalent Cr(2)S6 octahedra. Both Cr(1)-S(1) bond lengths are 2.41 Å. All Cr(1)-S(3) bond lengths are 2.41 Å. 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 CrS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Cr(1)S6 octahedra, edges with two equivalent Cr(2)S6 octahedra, and edges with two equivalent Ni(1)S6 octahedra. Both Cr(2)-S(1) bond lengths are 2.42 Å. Both Cr(2)-S(2) bond lengths are 2.41 Å. Both Cr(2)-S(3) bond lengths are 2.40 Å. Ni(1) is bonded to two equivalent S(2) and four equivalent S(3) atoms to form NiS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Cr(1)S6 octahedra, and edges with four equivalent Cr(2)S6 octahedra. Both Ni(1)-S(2) bond lengths are 2.36 Å. All Ni(1)-S(3) bond lengths are 2.38 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1), one Cr(1), and two equivalent Cr(2) atoms to form distorted SMgCr3 trigonal pyramids that share corners with three equivalent S(2)MgCr2Ni tetrahedra, corners with six equivalent S(3)MgCr2Ni tetrahedra, corners with three equivalent S(1)MgCr3 trigonal pyramids,  an edgeedge with one S(2)MgCr2Ni tetrahedra, and edges with two equivalent S(3)MgCr2Ni tetrahedra. In the second S site, S(2) is bonded to one Mg(1), two equivalent Cr(2), and one Ni(1) atom to form distorted SMgCr2Ni tetrahedra that share corners with three equivalent S(2)MgCr2Ni tetrahedra, corners with six equivalent S(3)MgCr2Ni tetrahedra, corners with three equivalent S(1)MgCr3 trigonal pyramids, edges with two equivalent S(3)MgCr2Ni tetrahedra, and  an edgeedge with one S(1)MgCr3 trigonal pyramid. In the third S site, S(3) is bonded to one Mg(1), one Cr(1), one Cr(2), and one Ni(1) atom to form distorted SMgCr2Ni tetrahedra that share corners with three equivalent S(2)MgCr2Ni tetrahedra, corners with six equivalent S(3)MgCr2Ni tetrahedra, corners with three equivalent S(1)MgCr3 trigonal pyramids,  an edgeedge with one S(2)MgCr2Ni tetrahedra,  an edgeedge with one S(3)MgCr2Ni tetrahedra, and  an edgeedge with one S(1)MgCr3 trigonal pyramid.