Ba5Nb2O10 crystallizes in the orthorhombic Cmc2_1 space group. There are five inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(6), one O(7), two equivalent O(2), two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Nb(1)O6 octahedra, and faces with three equivalent Nb(2)O6 octahedra. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one O(1), one O(6), one O(7), two equivalent O(2), and two equivalent O(3) atoms. In the third Ba site, Ba(3) is bonded in a 10-coordinate geometry to one O(1), one O(4), two equivalent O(5), two equivalent O(6), and four equivalent O(2) atoms. In the fourth Ba site, Ba(4) is bonded in a 10-coordinate geometry to one O(1), one O(4), two equivalent O(5), two equivalent O(7), and four equivalent O(3) atoms. In the fifth Ba site, Ba(5) is bonded in a 8-coordinate geometry to one O(6), one O(7), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(4), one O(6), two equivalent O(2), and two equivalent O(5) atoms to form distorted NbO6 octahedra that share faces with three equivalent Ba(1)O12 cuboctahedra and  a faceface with one Nb(2)O6 octahedra. In the second Nb site, Nb(2) is bonded to one O(4), one O(7), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share faces with three equivalent Ba(1)O12 cuboctahedra and  a faceface with one Nb(1)O6 octahedra. There are seven inequivalent O sites. In the first O site, O(5) is bonded to one Ba(3), one Ba(4), two equivalent Ba(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted corner and face-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 8-60°. In the second O site, O(6) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(3), and one Nb(1) atom. In the third O site, O(7) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(4), and one Nb(2) atom. In the fourth O site, O(1) is bonded in a 5-coordinate geometry to one Ba(2), one Ba(3), one Ba(4), and two equivalent Ba(5) atoms. In the fifth O site, O(2) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(3), and one Nb(1) atom. In the sixth O site, O(3) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(4), and one Nb(2) atom. In the seventh O site, O(4) is bonded to one Ba(3), one Ba(4), two equivalent Ba(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted corner and face-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 8-60°.
Ba5Nb2O10 crystallizes in the orthorhombic Cmc2_1 space group. There are five inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(6), one O(7), two equivalent O(2), two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms to form BaO12 cuboctahedra that share corners with six equivalent Ba(1)O12 cuboctahedra, faces with three equivalent Nb(1)O6 octahedra, and faces with three equivalent Nb(2)O6 octahedra. The Ba(1)-O(6) bond length is 3.22 Å. The Ba(1)-O(7) bond length is 3.02 Å. Both Ba(1)-O(2) bond lengths are 3.02 Å. Both Ba(1)-O(3) bond lengths are 3.13 Å. Both Ba(1)-O(4) bond lengths are 3.09 Å. There are two shorter (3.09 Å) and two longer (3.11 Å) Ba(1)-O(5) bond lengths. In the second Ba site, Ba(2) is bonded in a 7-coordinate geometry to one O(1), one O(6), one O(7), two equivalent O(2), and two equivalent O(3) atoms. The Ba(2)-O(1) bond length is 2.64 Å. The Ba(2)-O(6) bond length is 2.79 Å. The Ba(2)-O(7) bond length is 3.24 Å. Both Ba(2)-O(2) bond lengths are 2.56 Å. Both Ba(2)-O(3) bond lengths are 2.89 Å. In the third Ba site, Ba(3) is bonded in a 10-coordinate geometry to one O(1), one O(4), two equivalent O(5), two equivalent O(6), and four equivalent O(2) atoms. The Ba(3)-O(1) bond length is 2.57 Å. The Ba(3)-O(4) bond length is 2.95 Å. Both Ba(3)-O(5) bond lengths are 2.88 Å. Both Ba(3)-O(6) bond lengths are 3.12 Å. There are two shorter (2.97 Å) and two longer (3.24 Å) Ba(3)-O(2) bond lengths. In the fourth Ba site, Ba(4) is bonded in a 10-coordinate geometry to one O(1), one O(4), two equivalent O(5), two equivalent O(7), and four equivalent O(3) atoms. The Ba(4)-O(1) bond length is 2.57 Å. The Ba(4)-O(4) bond length is 2.85 Å. Both Ba(4)-O(5) bond lengths are 2.93 Å. Both Ba(4)-O(7) bond lengths are 3.09 Å. There are two shorter (3.01 Å) and two longer (3.22 Å) Ba(4)-O(3) bond lengths. In the fifth Ba site, Ba(5) is bonded in a 8-coordinate geometry to one O(6), one O(7), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Ba(5)-O(6) bond length is 2.79 Å. The Ba(5)-O(7) bond length is 2.50 Å. Both Ba(5)-O(1) bond lengths are 3.24 Å. Both Ba(5)-O(2) bond lengths are 3.13 Å. Both Ba(5)-O(3) bond lengths are 2.67 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(4), one O(6), two equivalent O(2), and two equivalent O(5) atoms to form distorted NbO6 octahedra that share faces with three equivalent Ba(1)O12 cuboctahedra and  a faceface with one Nb(2)O6 octahedra. The Nb(1)-O(4) bond length is 2.24 Å. The Nb(1)-O(6) bond length is 1.92 Å. Both Nb(1)-O(2) bond lengths are 1.94 Å. Both Nb(1)-O(5) bond lengths are 2.11 Å. In the second Nb site, Nb(2) is bonded to one O(4), one O(7), two equivalent O(3), and two equivalent O(5) atoms to form NbO6 octahedra that share faces with three equivalent Ba(1)O12 cuboctahedra and  a faceface with one Nb(1)O6 octahedra. The Nb(2)-O(4) bond length is 2.07 Å. The Nb(2)-O(7) bond length is 1.96 Å. Both Nb(2)-O(3) bond lengths are 1.93 Å. Both Nb(2)-O(5) bond lengths are 2.19 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded to one Ba(3), one Ba(4), two equivalent Ba(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted corner and face-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 8-60°. In the second O site, O(6) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(3), and one Nb(1) atom. In the third O site, O(7) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(4), and one Nb(2) atom. In the fourth O site, O(1) is bonded in a 5-coordinate geometry to one Ba(2), one Ba(3), one Ba(4), and two equivalent Ba(5) atoms. In the fifth O site, O(2) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(3), and one Nb(1) atom. In the sixth O site, O(3) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(2), one Ba(5), two equivalent Ba(4), and one Nb(2) atom. In the seventh O site, O(4) is bonded to one Ba(3), one Ba(4), two equivalent Ba(1), one Nb(1), and one Nb(2) atom to form a mixture of distorted corner and face-sharing OBa4Nb2 octahedra. The corner-sharing octahedral tilt angles range from 8-60°.