Mn3SiN4 is Enargite structured and crystallizes in the orthorhombic Pmn2_1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one N(2), one N(3), and three equivalent N(1) atoms to form distorted MnN5 trigonal bipyramids that share corners with three equivalent Si(1)N4 tetrahedra, corners with two equivalent Mn(2)N5 trigonal bipyramids, corners with four equivalent Mn(1)N5 trigonal bipyramids,  an edgeedge with one Si(1)N4 tetrahedra, edges with two equivalent Mn(1)N5 trigonal bipyramids, and edges with two equivalent Mn(2)N5 trigonal bipyramids. In the second Mn site, Mn(2) is bonded to one N(3), two equivalent N(1), and two equivalent N(2) atoms to form distorted MnN5 trigonal bipyramids that share corners with three equivalent Si(1)N4 tetrahedra, corners with two equivalent Mn(2)N5 trigonal bipyramids, corners with four equivalent Mn(1)N5 trigonal bipyramids,  an edgeedge with one Si(1)N4 tetrahedra, and edges with four equivalent Mn(1)N5 trigonal bipyramids. Si(1) is bonded to one N(2), one N(3), and two equivalent N(1) atoms to form SiN4 tetrahedra that share corners with three equivalent Mn(2)N5 trigonal bipyramids, corners with six equivalent Mn(1)N5 trigonal bipyramids,  an edgeedge with one Mn(2)N5 trigonal bipyramid, and edges with two equivalent Mn(1)N5 trigonal bipyramids. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Mn(2), three equivalent Mn(1), and one Si(1) atom to form distorted NMn4Si trigonal bipyramids that share corners with two equivalent N(2)Mn4Si trigonal bipyramids, corners with four equivalent N(1)Mn4Si trigonal bipyramids, corners with three equivalent N(3)Mn3Si trigonal pyramids, edges with two equivalent N(1)Mn4Si trigonal bipyramids, edges with two equivalent N(2)Mn4Si trigonal bipyramids, and  an edgeedge with one N(3)Mn3Si trigonal pyramid. In the second N site, N(2) is bonded to two equivalent Mn(1), two equivalent Mn(2), and one Si(1) atom to form distorted NMn4Si trigonal bipyramids that share corners with two equivalent N(2)Mn4Si trigonal bipyramids, corners with four equivalent N(1)Mn4Si trigonal bipyramids, corners with three equivalent N(3)Mn3Si trigonal pyramids, edges with four equivalent N(1)Mn4Si trigonal bipyramids, and  an edgeedge with one N(3)Mn3Si trigonal pyramid. In the third N site, N(3) is bonded to one Mn(2), two equivalent Mn(1), and one Si(1) atom to form a mixture of edge and corner-sharing NMn3Si trigonal pyramids.
Mn3SiN4 is Enargite structured and crystallizes in the orthorhombic Pmn2_1 space group. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one N(2), one N(3), and three equivalent N(1) atoms to form distorted MnN5 trigonal bipyramids that share corners with three equivalent Si(1)N4 tetrahedra, corners with two equivalent Mn(2)N5 trigonal bipyramids, corners with four equivalent Mn(1)N5 trigonal bipyramids,  an edgeedge with one Si(1)N4 tetrahedra, edges with two equivalent Mn(1)N5 trigonal bipyramids, and edges with two equivalent Mn(2)N5 trigonal bipyramids. The Mn(1)-N(2) bond length is 2.10 Å. The Mn(1)-N(3) bond length is 1.94 Å. There are a spread of Mn(1)-N(1) bond distances ranging from 2.01-2.34 Å. In the second Mn site, Mn(2) is bonded to one N(3), two equivalent N(1), and two equivalent N(2) atoms to form distorted MnN5 trigonal bipyramids that share corners with three equivalent Si(1)N4 tetrahedra, corners with two equivalent Mn(2)N5 trigonal bipyramids, corners with four equivalent Mn(1)N5 trigonal bipyramids,  an edgeedge with one Si(1)N4 tetrahedra, and edges with four equivalent Mn(1)N5 trigonal bipyramids. The Mn(2)-N(3) bond length is 1.94 Å. Both Mn(2)-N(1) bond lengths are 1.96 Å. There is one shorter (2.08 Å) and one longer (2.44 Å) Mn(2)-N(2) bond length. Si(1) is bonded to one N(2), one N(3), and two equivalent N(1) atoms to form SiN4 tetrahedra that share corners with three equivalent Mn(2)N5 trigonal bipyramids, corners with six equivalent Mn(1)N5 trigonal bipyramids,  an edgeedge with one Mn(2)N5 trigonal bipyramid, and edges with two equivalent Mn(1)N5 trigonal bipyramids. The Si(1)-N(2) bond length is 1.75 Å. The Si(1)-N(3) bond length is 1.77 Å. Both Si(1)-N(1) bond lengths are 1.74 Å. There are three inequivalent N sites. In the first N site, N(1) is bonded to one Mn(2), three equivalent Mn(1), and one Si(1) atom to form distorted NMn4Si trigonal bipyramids that share corners with two equivalent N(2)Mn4Si trigonal bipyramids, corners with four equivalent N(1)Mn4Si trigonal bipyramids, corners with three equivalent N(3)Mn3Si trigonal pyramids, edges with two equivalent N(1)Mn4Si trigonal bipyramids, edges with two equivalent N(2)Mn4Si trigonal bipyramids, and  an edgeedge with one N(3)Mn3Si trigonal pyramid. In the second N site, N(2) is bonded to two equivalent Mn(1), two equivalent Mn(2), and one Si(1) atom to form distorted NMn4Si trigonal bipyramids that share corners with two equivalent N(2)Mn4Si trigonal bipyramids, corners with four equivalent N(1)Mn4Si trigonal bipyramids, corners with three equivalent N(3)Mn3Si trigonal pyramids, edges with four equivalent N(1)Mn4Si trigonal bipyramids, and  an edgeedge with one N(3)Mn3Si trigonal pyramid. In the third N site, N(3) is bonded to one Mn(2), two equivalent Mn(1), and one Si(1) atom to form a mixture of edge and corner-sharing NMn3Si trigonal pyramids.