Li2Sr2Nb4O13 crystallizes in the tetragonal I4/mmm space group. Li(1) is bonded in a 4-coordinate geometry to four equivalent O(4) atoms. Sr(1) is bonded to four equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Nb(1)O6 octahedra, and faces with four equivalent Nb(2)O6 octahedra. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(5), and four equivalent O(2) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra, corners with five equivalent Nb(1)O6 octahedra, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-12°. In the second Nb site, Nb(2) is bonded to one O(4), one O(5), and four equivalent O(3) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Sr(1) and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Sr(1) and two equivalent Nb(2) atoms. In the fourth O site, O(4) is bonded to four equivalent Li(1) and one Nb(2) atom to form distorted OLi4Nb trigonal bipyramids that share  a cornercorner with one O(5)Sr4Nb2 octahedra, corners with four equivalent O(4)Li4Nb trigonal bipyramids, and edges with four equivalent O(4)Li4Nb trigonal bipyramids. The corner-sharing octahedra are not tilted. In the fifth O site, O(5) is bonded to four equivalent Sr(1), one Nb(1), and one Nb(2) atom to form distorted OSr4Nb2 octahedra that share corners with four equivalent O(5)Sr4Nb2 octahedra,  a cornercorner with one O(4)Li4Nb trigonal bipyramid, and edges with four equivalent O(5)Sr4Nb2 octahedra. The corner-sharing octahedral tilt angles are 1°.
Li2Sr2Nb4O13 crystallizes in the tetragonal I4/mmm space group. Li(1) is bonded in a 4-coordinate geometry to four equivalent O(4) atoms. All Li(1)-O(4) bond lengths are 2.08 Å. Sr(1) is bonded to four equivalent O(2), four equivalent O(3), and four equivalent O(5) atoms to form SrO12 cuboctahedra that share corners with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Sr(1)O12 cuboctahedra, faces with four equivalent Nb(1)O6 octahedra, and faces with four equivalent Nb(2)O6 octahedra. All Sr(1)-O(2) bond lengths are 2.74 Å. All Sr(1)-O(3) bond lengths are 2.80 Å. All Sr(1)-O(5) bond lengths are 2.83 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(1), one O(5), and four equivalent O(2) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra, corners with five equivalent Nb(1)O6 octahedra, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-12°. The Nb(1)-O(1) bond length is 1.94 Å. The Nb(1)-O(5) bond length is 2.10 Å. All Nb(1)-O(2) bond lengths are 2.01 Å. In the second Nb site, Nb(2) is bonded to one O(4), one O(5), and four equivalent O(3) atoms to form NbO6 octahedra that share  a cornercorner with one Nb(1)O6 octahedra, corners with four equivalent Nb(2)O6 octahedra, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-11°. The Nb(2)-O(4) bond length is 1.90 Å. The Nb(2)-O(5) bond length is 2.14 Å. All Nb(2)-O(3) bond lengths are 2.01 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Sr(1) and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Sr(1) and two equivalent Nb(2) atoms. In the fourth O site, O(4) is bonded to four equivalent Li(1) and one Nb(2) atom to form distorted OLi4Nb trigonal bipyramids that share  a cornercorner with one O(5)Sr4Nb2 octahedra, corners with four equivalent O(4)Li4Nb trigonal bipyramids, and edges with four equivalent O(4)Li4Nb trigonal bipyramids. The corner-sharing octahedra are not tilted. In the fifth O site, O(5) is bonded to four equivalent Sr(1), one Nb(1), and one Nb(2) atom to form distorted OSr4Nb2 octahedra that share corners with four equivalent O(5)Sr4Nb2 octahedra,  a cornercorner with one O(4)Li4Nb trigonal bipyramid, and edges with four equivalent O(5)Sr4Nb2 octahedra. The corner-sharing octahedral tilt angles are 1°.