Sr5NbN5 crystallizes in the orthorhombic Pbcm space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent N(1) and two equivalent N(4) atoms to form distorted SrN4 trigonal pyramids that share corners with six equivalent Sr(4)N5 square pyramids, corners with two equivalent Nb(1)N4 tetrahedra, corners with two equivalent Sr(2)N5 trigonal bipyramids, corners with two equivalent Sr(1)N4 trigonal pyramids, edges with two equivalent Sr(2)N5 trigonal bipyramids, and edges with two equivalent Sr(3)N5 trigonal bipyramids. In the second Sr site, Sr(2) is bonded to one N(1) and four equivalent N(4) atoms to form distorted SrN5 trigonal bipyramids that share corners with two equivalent Sr(4)N5 square pyramids, corners with two equivalent Nb(1)N4 tetrahedra, corners with three equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(1)N4 trigonal pyramids, edges with two equivalent Sr(4)N5 square pyramids,  an edgeedge with one Nb(1)N4 tetrahedra,  an edgeedge with one Sr(3)N5 trigonal bipyramid, edges with two equivalent Sr(2)N5 trigonal bipyramids, and edges with two equivalent Sr(1)N4 trigonal pyramids. In the third Sr site, Sr(3) is bonded to one N(1), one N(2), one N(3), and two equivalent N(4) atoms to form SrN5 trigonal bipyramids that share corners with two equivalent Sr(4)N5 square pyramids, corners with four equivalent Nb(1)N4 tetrahedra, corners with three equivalent Sr(2)N5 trigonal bipyramids, edges with four equivalent Sr(4)N5 square pyramids,  an edgeedge with one Sr(2)N5 trigonal bipyramid, and edges with two equivalent Sr(1)N4 trigonal pyramids. In the fourth Sr site, Sr(4) is bonded to one N(1), one N(3), one N(4), and two equivalent N(2) atoms to form distorted SrN5 square pyramids that share corners with two equivalent Sr(4)N5 square pyramids, corners with two equivalent Nb(1)N4 tetrahedra,  a cornercorner with one Sr(2)N5 trigonal bipyramid,  a cornercorner with one Sr(3)N5 trigonal bipyramid, corners with three equivalent Sr(1)N4 trigonal pyramids, edges with three equivalent Sr(4)N5 square pyramids,  an edgeedge with one Nb(1)N4 tetrahedra,  an edgeedge with one Sr(2)N5 trigonal bipyramid, and edges with two equivalent Sr(3)N5 trigonal bipyramids. Nb(1) is bonded to one N(2), one N(3), and two equivalent N(4) atoms to form NbN4 tetrahedra that share corners with four equivalent Sr(4)N5 square pyramids, corners with two equivalent Sr(2)N5 trigonal bipyramids, corners with four equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(1)N4 trigonal pyramids, edges with two equivalent Sr(4)N5 square pyramids, and  an edgeedge with one Sr(2)N5 trigonal bipyramid. There are four inequivalent N sites. In the first N site, N(4) is bonded to one Sr(1), one Sr(3), one Sr(4), two equivalent Sr(2), and one Nb(1) atom to form distorted NSr5Nb octahedra that share corners with two equivalent N(4)Sr5Nb octahedra, corners with two equivalent N(1)Sr6 octahedra, edges with two equivalent N(2)Sr5Nb octahedra, edges with two equivalent N(4)Sr5Nb octahedra, edges with two equivalent N(1)Sr6 octahedra, and  a faceface with one N(4)Sr5Nb octahedra. The corner-sharing octahedral tilt angles range from 46-51°. In the second N site, N(1) is bonded to one Sr(2), one Sr(3), two equivalent Sr(1), and two equivalent Sr(4) atoms to form NSr6 octahedra that share corners with two equivalent N(1)Sr6 octahedra, corners with three equivalent N(2)Sr5Nb octahedra, corners with four equivalent N(4)Sr5Nb octahedra,  an edgeedge with one N(2)Sr5Nb octahedra, and edges with four equivalent N(4)Sr5Nb octahedra. The corner-sharing octahedral tilt angles range from 3-55°. In the third N site, N(2) is bonded to one Sr(3), four equivalent Sr(4), and one Nb(1) atom to form distorted NSr5Nb octahedra that share corners with three equivalent N(1)Sr6 octahedra,  an edgeedge with one N(1)Sr6 octahedra, edges with two equivalent N(2)Sr5Nb octahedra, and edges with four equivalent N(4)Sr5Nb octahedra. The corner-sharing octahedral tilt angles range from 3-17°. In the fourth N site, N(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(3), two equivalent Sr(4), and one Nb(1) atom.
Sr5NbN5 crystallizes in the orthorhombic Pbcm space group. There are four inequivalent Sr sites. In the first Sr site, Sr(1) is bonded to two equivalent N(1) and two equivalent N(4) atoms to form distorted SrN4 trigonal pyramids that share corners with six equivalent Sr(4)N5 square pyramids, corners with two equivalent Nb(1)N4 tetrahedra, corners with two equivalent Sr(2)N5 trigonal bipyramids, corners with two equivalent Sr(1)N4 trigonal pyramids, edges with two equivalent Sr(2)N5 trigonal bipyramids, and edges with two equivalent Sr(3)N5 trigonal bipyramids. Both Sr(1)-N(1) bond lengths are 2.56 Å. Both Sr(1)-N(4) bond lengths are 2.67 Å. In the second Sr site, Sr(2) is bonded to one N(1) and four equivalent N(4) atoms to form distorted SrN5 trigonal bipyramids that share corners with two equivalent Sr(4)N5 square pyramids, corners with two equivalent Nb(1)N4 tetrahedra, corners with three equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(1)N4 trigonal pyramids, edges with two equivalent Sr(4)N5 square pyramids,  an edgeedge with one Nb(1)N4 tetrahedra,  an edgeedge with one Sr(3)N5 trigonal bipyramid, edges with two equivalent Sr(2)N5 trigonal bipyramids, and edges with two equivalent Sr(1)N4 trigonal pyramids. The Sr(2)-N(1) bond length is 2.53 Å. There are two shorter (2.71 Å) and two longer (2.75 Å) Sr(2)-N(4) bond lengths. In the third Sr site, Sr(3) is bonded to one N(1), one N(2), one N(3), and two equivalent N(4) atoms to form SrN5 trigonal bipyramids that share corners with two equivalent Sr(4)N5 square pyramids, corners with four equivalent Nb(1)N4 tetrahedra, corners with three equivalent Sr(2)N5 trigonal bipyramids, edges with four equivalent Sr(4)N5 square pyramids,  an edgeedge with one Sr(2)N5 trigonal bipyramid, and edges with two equivalent Sr(1)N4 trigonal pyramids. The Sr(3)-N(1) bond length is 2.74 Å. The Sr(3)-N(2) bond length is 2.82 Å. The Sr(3)-N(3) bond length is 2.65 Å. Both Sr(3)-N(4) bond lengths are 2.69 Å. In the fourth Sr site, Sr(4) is bonded to one N(1), one N(3), one N(4), and two equivalent N(2) atoms to form distorted SrN5 square pyramids that share corners with two equivalent Sr(4)N5 square pyramids, corners with two equivalent Nb(1)N4 tetrahedra,  a cornercorner with one Sr(2)N5 trigonal bipyramid,  a cornercorner with one Sr(3)N5 trigonal bipyramid, corners with three equivalent Sr(1)N4 trigonal pyramids, edges with three equivalent Sr(4)N5 square pyramids,  an edgeedge with one Nb(1)N4 tetrahedra,  an edgeedge with one Sr(2)N5 trigonal bipyramid, and edges with two equivalent Sr(3)N5 trigonal bipyramids. The Sr(4)-N(1) bond length is 2.72 Å. The Sr(4)-N(3) bond length is 2.67 Å. The Sr(4)-N(4) bond length is 2.71 Å. There is one shorter (2.63 Å) and one longer (2.68 Å) Sr(4)-N(2) bond length. Nb(1) is bonded to one N(2), one N(3), and two equivalent N(4) atoms to form NbN4 tetrahedra that share corners with four equivalent Sr(4)N5 square pyramids, corners with two equivalent Sr(2)N5 trigonal bipyramids, corners with four equivalent Sr(3)N5 trigonal bipyramids, corners with two equivalent Sr(1)N4 trigonal pyramids, edges with two equivalent Sr(4)N5 square pyramids, and  an edgeedge with one Sr(2)N5 trigonal bipyramid. The Nb(1)-N(2) bond length is 1.97 Å. The Nb(1)-N(3) bond length is 1.98 Å. Both Nb(1)-N(4) bond lengths are 2.01 Å. There are four inequivalent N sites. In the first N site, N(4) is bonded to one Sr(1), one Sr(3), one Sr(4), two equivalent Sr(2), and one Nb(1) atom to form distorted NSr5Nb octahedra that share corners with two equivalent N(4)Sr5Nb octahedra, corners with two equivalent N(1)Sr6 octahedra, edges with two equivalent N(2)Sr5Nb octahedra, edges with two equivalent N(4)Sr5Nb octahedra, edges with two equivalent N(1)Sr6 octahedra, and  a faceface with one N(4)Sr5Nb octahedra. The corner-sharing octahedral tilt angles range from 46-51°. In the second N site, N(1) is bonded to one Sr(2), one Sr(3), two equivalent Sr(1), and two equivalent Sr(4) atoms to form NSr6 octahedra that share corners with two equivalent N(1)Sr6 octahedra, corners with three equivalent N(2)Sr5Nb octahedra, corners with four equivalent N(4)Sr5Nb octahedra,  an edgeedge with one N(2)Sr5Nb octahedra, and edges with four equivalent N(4)Sr5Nb octahedra. The corner-sharing octahedral tilt angles range from 3-55°. In the third N site, N(2) is bonded to one Sr(3), four equivalent Sr(4), and one Nb(1) atom to form distorted NSr5Nb octahedra that share corners with three equivalent N(1)Sr6 octahedra,  an edgeedge with one N(1)Sr6 octahedra, edges with two equivalent N(2)Sr5Nb octahedra, and edges with four equivalent N(4)Sr5Nb octahedra. The corner-sharing octahedral tilt angles range from 3-17°. In the fourth N site, N(3) is bonded in a distorted rectangular see-saw-like geometry to one Sr(3), two equivalent Sr(4), and one Nb(1) atom.