Mg3(GaN2)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(2) and three equivalent N(1) atoms to form distorted MgN5 trigonal bipyramids that share corners with six equivalent Ga(1)N4 tetrahedra, corners with two equivalent Mg(1)N5 trigonal bipyramids, edges with two equivalent Ga(1)N4 tetrahedra, and edges with three equivalent Mg(1)N5 trigonal bipyramids. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent N(1) and four equivalent N(2) atoms. Ga(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form distorted GaN4 tetrahedra that share corners with two equivalent Ga(1)N4 tetrahedra, corners with six equivalent Mg(1)N5 trigonal bipyramids,  an edgeedge with one Ga(1)N4 tetrahedra, and edges with two equivalent Mg(1)N5 trigonal bipyramids. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Mg(2), three equivalent Mg(1), and two equivalent Ga(1) atoms to form a mixture of distorted edge and corner-sharing NMg4Ga2 pentagonal pyramids. In the second N site, N(2) is bonded in a 6-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Ga(1) atoms.
Mg3(GaN2)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent N(2) and three equivalent N(1) atoms to form distorted MgN5 trigonal bipyramids that share corners with six equivalent Ga(1)N4 tetrahedra, corners with two equivalent Mg(1)N5 trigonal bipyramids, edges with two equivalent Ga(1)N4 tetrahedra, and edges with three equivalent Mg(1)N5 trigonal bipyramids. There is one shorter (2.21 Å) and one longer (2.32 Å) Mg(1)-N(2) bond length. There are a spread of Mg(1)-N(1) bond distances ranging from 2.17-2.36 Å. In the second Mg site, Mg(2) is bonded in a 6-coordinate geometry to two equivalent N(1) and four equivalent N(2) atoms. Both Mg(2)-N(1) bond lengths are 2.33 Å. There are two shorter (2.12 Å) and two longer (2.65 Å) Mg(2)-N(2) bond lengths. Ga(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form distorted GaN4 tetrahedra that share corners with two equivalent Ga(1)N4 tetrahedra, corners with six equivalent Mg(1)N5 trigonal bipyramids,  an edgeedge with one Ga(1)N4 tetrahedra, and edges with two equivalent Mg(1)N5 trigonal bipyramids. There is one shorter (2.02 Å) and one longer (2.03 Å) Ga(1)-N(1) bond length. Both Ga(1)-N(2) bond lengths are 1.93 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded to one Mg(2), three equivalent Mg(1), and two equivalent Ga(1) atoms to form a mixture of distorted edge and corner-sharing NMg4Ga2 pentagonal pyramids. In the second N site, N(2) is bonded in a 6-coordinate geometry to two equivalent Mg(1), two equivalent Mg(2), and two equivalent Ga(1) atoms.