Mg2Mo3NiS8 is Spinel-derived structured and crystallizes in the trigonal R-3m space group. Mg(1) is bonded to one S(1) and three equivalent S(2) atoms to form MgS4 tetrahedra that share corners with three equivalent Ni(1)S6 octahedra and corners with nine equivalent Mo(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 58-60°. Mo(1) is bonded to two equivalent S(1) and four equivalent S(2) atoms to form MoS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(1)S6 octahedra, and edges with four equivalent Mo(1)S6 octahedra. Ni(1) is bonded to six equivalent S(2) atoms to form NiS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra and edges with six equivalent Mo(1)S6 octahedra. There are two inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1) and three equivalent Mo(1) atoms to form distorted SMgMo3 trigonal pyramids that share corners with three equivalent S(1)MgMo3 trigonal pyramids, corners with nine equivalent S(2)MgNiMo2 trigonal pyramids, and edges with three equivalent S(2)MgNiMo2 trigonal pyramids. In the second S site, S(2) is bonded to one Mg(1), two equivalent Mo(1), and one Ni(1) atom to form distorted SMgNiMo2 trigonal pyramids that share corners with three equivalent S(1)MgMo3 trigonal pyramids, corners with nine equivalent S(2)MgNiMo2 trigonal pyramids,  an edgeedge with one S(1)MgMo3 trigonal pyramid, and edges with two equivalent S(2)MgNiMo2 trigonal pyramids.
Mg2Mo3NiS8 is Spinel-derived structured and crystallizes in the trigonal R-3m space group. Mg(1) is bonded to one S(1) and three equivalent S(2) atoms to form MgS4 tetrahedra that share corners with three equivalent Ni(1)S6 octahedra and corners with nine equivalent Mo(1)S6 octahedra. The corner-sharing octahedral tilt angles range from 58-60°. The Mg(1)-S(1) bond length is 2.45 Å. All Mg(1)-S(2) bond lengths are 2.46 Å. Mo(1) is bonded to two equivalent S(1) and four equivalent S(2) atoms to form MoS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra, edges with two equivalent Ni(1)S6 octahedra, and edges with four equivalent Mo(1)S6 octahedra. Both Mo(1)-S(1) bond lengths are 2.48 Å. All Mo(1)-S(2) bond lengths are 2.48 Å. Ni(1) is bonded to six equivalent S(2) atoms to form NiS6 octahedra that share corners with six equivalent Mg(1)S4 tetrahedra and edges with six equivalent Mo(1)S6 octahedra. All Ni(1)-S(2) bond lengths are 2.45 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one Mg(1) and three equivalent Mo(1) atoms to form distorted SMgMo3 trigonal pyramids that share corners with three equivalent S(1)MgMo3 trigonal pyramids, corners with nine equivalent S(2)MgNiMo2 trigonal pyramids, and edges with three equivalent S(2)MgNiMo2 trigonal pyramids. In the second S site, S(2) is bonded to one Mg(1), two equivalent Mo(1), and one Ni(1) atom to form distorted SMgNiMo2 trigonal pyramids that share corners with three equivalent S(1)MgMo3 trigonal pyramids, corners with nine equivalent S(2)MgNiMo2 trigonal pyramids,  an edgeedge with one S(1)MgMo3 trigonal pyramid, and edges with two equivalent S(2)MgNiMo2 trigonal pyramids.