Li4Ca2Mg(SiN3)2 crystallizes in the monoclinic C2/m space group. Li(1) is bonded to one N(1) and three equivalent N(2) atoms to form LiN4 tetrahedra that share corners with four equivalent Ca(1)N6 octahedra, corners with three equivalent Li(1)N4 tetrahedra, corners with three equivalent Si(1)N4 tetrahedra, edges with two equivalent Ca(1)N6 octahedra,  an edgeedge with one Si(1)N4 tetrahedra, and edges with two equivalent Li(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 22-64°. Ca(1) is bonded to two equivalent N(1) and four equivalent N(2) atoms to form CaN6 octahedra that share corners with four equivalent Si(1)N4 tetrahedra, corners with eight equivalent Li(1)N4 tetrahedra, edges with three equivalent Ca(1)N6 octahedra, edges with two equivalent Si(1)N4 tetrahedra, and edges with four equivalent Li(1)N4 tetrahedra. Mg(1) is bonded in a distorted square co-planar geometry to four equivalent N(2) atoms. Si(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form SiN4 tetrahedra that share corners with four equivalent Ca(1)N6 octahedra, corners with six equivalent Li(1)N4 tetrahedra, edges with two equivalent Ca(1)N6 octahedra,  an edgeedge with one Si(1)N4 tetrahedra, and edges with two equivalent Li(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-45°. There are two inequivalent N sites. In the first N site, N(1) is bonded in a 6-coordinate geometry to two equivalent Li(1), two equivalent Ca(1), and two equivalent Si(1) atoms. In the second N site, N(2) is bonded in a 7-coordinate geometry to three equivalent Li(1), two equivalent Ca(1), one Mg(1), and one Si(1) atom.
Li4Ca2Mg(SiN3)2 crystallizes in the monoclinic C2/m space group. Li(1) is bonded to one N(1) and three equivalent N(2) atoms to form LiN4 tetrahedra that share corners with four equivalent Ca(1)N6 octahedra, corners with three equivalent Li(1)N4 tetrahedra, corners with three equivalent Si(1)N4 tetrahedra, edges with two equivalent Ca(1)N6 octahedra,  an edgeedge with one Si(1)N4 tetrahedra, and edges with two equivalent Li(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 22-64°. The Li(1)-N(1) bond length is 2.13 Å. There are a spread of Li(1)-N(2) bond distances ranging from 2.13-2.20 Å. Ca(1) is bonded to two equivalent N(1) and four equivalent N(2) atoms to form CaN6 octahedra that share corners with four equivalent Si(1)N4 tetrahedra, corners with eight equivalent Li(1)N4 tetrahedra, edges with three equivalent Ca(1)N6 octahedra, edges with two equivalent Si(1)N4 tetrahedra, and edges with four equivalent Li(1)N4 tetrahedra. Both Ca(1)-N(1) bond lengths are 2.55 Å. There are two shorter (2.43 Å) and two longer (2.50 Å) Ca(1)-N(2) bond lengths. Mg(1) is bonded in a distorted square co-planar geometry to four equivalent N(2) atoms. All Mg(1)-N(2) bond lengths are 2.21 Å. Si(1) is bonded to two equivalent N(1) and two equivalent N(2) atoms to form SiN4 tetrahedra that share corners with four equivalent Ca(1)N6 octahedra, corners with six equivalent Li(1)N4 tetrahedra, edges with two equivalent Ca(1)N6 octahedra,  an edgeedge with one Si(1)N4 tetrahedra, and edges with two equivalent Li(1)N4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-45°. There is one shorter (1.81 Å) and one longer (1.83 Å) Si(1)-N(1) bond length. Both Si(1)-N(2) bond lengths are 1.75 Å. There are two inequivalent N sites. In the first N site, N(1) is bonded in a 6-coordinate geometry to two equivalent Li(1), two equivalent Ca(1), and two equivalent Si(1) atoms. In the second N site, N(2) is bonded in a 7-coordinate geometry to three equivalent Li(1), two equivalent Ca(1), one Mg(1), and one Si(1) atom.