CsSr2Nb3O10 crystallizes in the tetragonal P4/mmm space group. Cs(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. Sr(1) is bonded to four equivalent O(2), four equivalent O(3), and four equivalent O(4) atoms to form distorted SrO12 cuboctahedra that share corners with eight equivalent Sr(1)O12 cuboctahedra, faces with five equivalent Sr(1)O12 cuboctahedra, and faces with four equivalent Nb(2)O6 octahedra. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), and four equivalent O(2) atoms. In the second Nb site, Nb(2) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form NbO6 octahedra that share corners with four equivalent Nb(2)O6 octahedra and faces with eight equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. There are four inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to four equivalent Cs(1) and one Nb(1) atom. In the second O site, O(2) is bonded to two equivalent Sr(1) and two equivalent Nb(1) atoms to form distorted OSr2Nb2 trigonal pyramids that share corners with four equivalent O(4)Sr4Nb2 octahedra, corners with four equivalent O(2)Sr2Nb2 trigonal pyramids, edges with four equivalent O(2)Sr2Nb2 trigonal pyramids, and faces with two equivalent O(4)Sr4Nb2 octahedra. The corner-sharing octahedral tilt angles are 53°. In the third O site, O(3) is bonded in a linear geometry to four equivalent Sr(1) and two equivalent Nb(2) atoms. In the fourth O site, O(4) is bonded to four equivalent Sr(1), one Nb(1), and one Nb(2) atom to form distorted OSr4Nb2 octahedra that share corners with five equivalent O(4)Sr4Nb2 octahedra, corners with eight equivalent O(2)Sr2Nb2 trigonal pyramids, edges with four equivalent O(4)Sr4Nb2 octahedra, and faces with four equivalent O(2)Sr2Nb2 trigonal pyramids. The corner-sharing octahedral tilt angles range from 0-12°.
CsSr2Nb3O10 crystallizes in the tetragonal P4/mmm space group. Cs(1) is bonded in a body-centered cubic geometry to eight equivalent O(1) atoms. All Cs(1)-O(1) bond lengths are 3.26 Å. Sr(1) is bonded to four equivalent O(2), four equivalent O(3), and four equivalent O(4) atoms to form distorted SrO12 cuboctahedra that share corners with eight equivalent Sr(1)O12 cuboctahedra, faces with five equivalent Sr(1)O12 cuboctahedra, and faces with four equivalent Nb(2)O6 octahedra. All Sr(1)-O(2) bond lengths are 2.65 Å. All Sr(1)-O(3) bond lengths are 3.03 Å. All Sr(1)-O(4) bond lengths are 2.84 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), and four equivalent O(2) atoms. The Nb(1)-O(1) bond length is 1.79 Å. The Nb(1)-O(4) bond length is 2.43 Å. All Nb(1)-O(2) bond lengths are 2.04 Å. In the second Nb site, Nb(2) is bonded to two equivalent O(4) and four equivalent O(3) atoms to form NbO6 octahedra that share corners with four equivalent Nb(2)O6 octahedra and faces with eight equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Nb(2)-O(4) bond lengths are 1.99 Å. All Nb(2)-O(3) bond lengths are 2.00 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to four equivalent Cs(1) and one Nb(1) atom. In the second O site, O(2) is bonded to two equivalent Sr(1) and two equivalent Nb(1) atoms to form distorted OSr2Nb2 trigonal pyramids that share corners with four equivalent O(4)Sr4Nb2 octahedra, corners with four equivalent O(2)Sr2Nb2 trigonal pyramids, edges with four equivalent O(2)Sr2Nb2 trigonal pyramids, and faces with two equivalent O(4)Sr4Nb2 octahedra. The corner-sharing octahedral tilt angles are 53°. In the third O site, O(3) is bonded in a linear geometry to four equivalent Sr(1) and two equivalent Nb(2) atoms. In the fourth O site, O(4) is bonded to four equivalent Sr(1), one Nb(1), and one Nb(2) atom to form distorted OSr4Nb2 octahedra that share corners with five equivalent O(4)Sr4Nb2 octahedra, corners with eight equivalent O(2)Sr2Nb2 trigonal pyramids, edges with four equivalent O(4)Sr4Nb2 octahedra, and faces with four equivalent O(2)Sr2Nb2 trigonal pyramids. The corner-sharing octahedral tilt angles range from 0-12°.