Ba4SiN4 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 5-coordinate geometry to one N(2), two equivalent N(1), and two equivalent N(3) atoms. In the second Ba site, Ba(2) is bonded to one N(3), two equivalent N(2), and three equivalent N(4) atoms to form BaN6 octahedra that share  a cornercorner with one Ba(3)N5 square pyramid, edges with four equivalent Ba(2)N6 octahedra, and edges with two equivalent Ba(3)N5 square pyramids. In the third Ba site, Ba(3) is bonded to one N(4), two equivalent N(1), and two equivalent N(3) atoms to form distorted BaN5 square pyramids that share  a cornercorner with one Ba(2)N6 octahedra, edges with two equivalent Ba(2)N6 octahedra, and edges with two equivalent Ba(3)N5 square pyramids. The corner-sharing octahedral tilt angles are 9°. In the fourth Ba site, Ba(4) is bonded in a distorted rectangular see-saw-like geometry to one N(2), one N(3), and two equivalent N(4) atoms. Si(1) is bonded in a bent 150 degrees geometry to one N(1) and one N(2) atom. There are four inequivalent N sites. In the first N site, N(4) is bonded to one Ba(3), two equivalent Ba(4), and three equivalent Ba(2) atoms to form NBa6 octahedra that share corners with three equivalent N(3)Ba6 octahedra, corners with two equivalent N(2)Ba4Si trigonal bipyramids, edges with two equivalent N(3)Ba6 octahedra, edges with four equivalent N(4)Ba6 octahedra, and edges with three equivalent N(2)Ba4Si trigonal bipyramids. The corner-sharing octahedral tilt angles range from 4-55°. In the second N site, N(1) is bonded in a distorted single-bond geometry to two equivalent Ba(1), two equivalent Ba(3), and one Si(1) atom. In the third N site, N(2) is bonded to one Ba(1), one Ba(4), two equivalent Ba(2), and one Si(1) atom to form distorted NBa4Si trigonal bipyramids that share  a cornercorner with one N(3)Ba6 octahedra, corners with two equivalent N(4)Ba6 octahedra, corners with two equivalent N(2)Ba4Si trigonal bipyramids, edges with two equivalent N(3)Ba6 octahedra, and edges with three equivalent N(4)Ba6 octahedra. The corner-sharing octahedral tilt angles range from 5-67°. In the fourth N site, N(3) is bonded to one Ba(2), one Ba(4), two equivalent Ba(1), and two equivalent Ba(3) atoms to form NBa6 octahedra that share corners with three equivalent N(4)Ba6 octahedra,  a cornercorner with one N(2)Ba4Si trigonal bipyramid, edges with two equivalent N(3)Ba6 octahedra, edges with two equivalent N(4)Ba6 octahedra, and edges with two equivalent N(2)Ba4Si trigonal bipyramids. The corner-sharing octahedral tilt angles range from 4-55°.
Ba4SiN4 crystallizes in the orthorhombic Pnma space group. There are four inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 5-coordinate geometry to one N(2), two equivalent N(1), and two equivalent N(3) atoms. The Ba(1)-N(2) bond length is 2.96 Å. Both Ba(1)-N(1) bond lengths are 3.02 Å. Both Ba(1)-N(3) bond lengths are 2.74 Å. In the second Ba site, Ba(2) is bonded to one N(3), two equivalent N(2), and three equivalent N(4) atoms to form BaN6 octahedra that share  a cornercorner with one Ba(3)N5 square pyramid, edges with four equivalent Ba(2)N6 octahedra, and edges with two equivalent Ba(3)N5 square pyramids. The Ba(2)-N(3) bond length is 3.15 Å. Both Ba(2)-N(2) bond lengths are 2.90 Å. There are two shorter (2.93 Å) and one longer (3.02 Å) Ba(2)-N(4) bond length. In the third Ba site, Ba(3) is bonded to one N(4), two equivalent N(1), and two equivalent N(3) atoms to form distorted BaN5 square pyramids that share  a cornercorner with one Ba(2)N6 octahedra, edges with two equivalent Ba(2)N6 octahedra, and edges with two equivalent Ba(3)N5 square pyramids. The corner-sharing octahedral tilt angles are 9°. The Ba(3)-N(4) bond length is 2.69 Å. Both Ba(3)-N(1) bond lengths are 2.93 Å. Both Ba(3)-N(3) bond lengths are 2.79 Å. In the fourth Ba site, Ba(4) is bonded in a distorted rectangular see-saw-like geometry to one N(2), one N(3), and two equivalent N(4) atoms. The Ba(4)-N(2) bond length is 3.02 Å. The Ba(4)-N(3) bond length is 2.86 Å. Both Ba(4)-N(4) bond lengths are 2.69 Å. Si(1) is bonded in a bent 150 degrees geometry to one N(1) and one N(2) atom. The Si(1)-N(1) bond length is 1.63 Å. The Si(1)-N(2) bond length is 1.64 Å. There are four inequivalent N sites. In the first N site, N(4) is bonded to one Ba(3), two equivalent Ba(4), and three equivalent Ba(2) atoms to form NBa6 octahedra that share corners with three equivalent N(3)Ba6 octahedra, corners with two equivalent N(2)Ba4Si trigonal bipyramids, edges with two equivalent N(3)Ba6 octahedra, edges with four equivalent N(4)Ba6 octahedra, and edges with three equivalent N(2)Ba4Si trigonal bipyramids. The corner-sharing octahedral tilt angles range from 4-55°. In the second N site, N(1) is bonded in a distorted single-bond geometry to two equivalent Ba(1), two equivalent Ba(3), and one Si(1) atom. In the third N site, N(2) is bonded to one Ba(1), one Ba(4), two equivalent Ba(2), and one Si(1) atom to form distorted NBa4Si trigonal bipyramids that share  a cornercorner with one N(3)Ba6 octahedra, corners with two equivalent N(4)Ba6 octahedra, corners with two equivalent N(2)Ba4Si trigonal bipyramids, edges with two equivalent N(3)Ba6 octahedra, and edges with three equivalent N(4)Ba6 octahedra. The corner-sharing octahedral tilt angles range from 5-67°. In the fourth N site, N(3) is bonded to one Ba(2), one Ba(4), two equivalent Ba(1), and two equivalent Ba(3) atoms to form NBa6 octahedra that share corners with three equivalent N(4)Ba6 octahedra,  a cornercorner with one N(2)Ba4Si trigonal bipyramid, edges with two equivalent N(3)Ba6 octahedra, edges with two equivalent N(4)Ba6 octahedra, and edges with two equivalent N(2)Ba4Si trigonal bipyramids. The corner-sharing octahedral tilt angles range from 4-55°.