Ba3Nb2P4O18 crystallizes in the triclinic P-1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to one O(2), one O(5), one O(6), two equivalent O(3), two equivalent O(9), and three equivalent O(8) atoms. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to two equivalent O(4), two equivalent O(7), two equivalent O(9), and four equivalent O(2) atoms. Nb(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted NbO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(5), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-45°. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(9) atom to form PO4 tetrahedra that share corners with three equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-45°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Nb(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one P(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one Nb(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(2), one Nb(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ba(1), one Nb(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ba(1), one Nb(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ba(2), one Nb(1), and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one P(1) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one P(2) atom.
Ba3Nb2P4O18 crystallizes in the triclinic P-1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to one O(2), one O(5), one O(6), two equivalent O(3), two equivalent O(9), and three equivalent O(8) atoms. The Ba(1)-O(2) bond length is 2.95 Å. The Ba(1)-O(5) bond length is 3.03 Å. The Ba(1)-O(6) bond length is 2.82 Å. There is one shorter (2.89 Å) and one longer (3.23 Å) Ba(1)-O(3) bond length. There is one shorter (2.90 Å) and one longer (3.04 Å) Ba(1)-O(9) bond length. There are a spread of Ba(1)-O(8) bond distances ranging from 2.79-3.38 Å. In the second Ba site, Ba(2) is bonded in a 10-coordinate geometry to two equivalent O(4), two equivalent O(7), two equivalent O(9), and four equivalent O(2) atoms. Both Ba(2)-O(4) bond lengths are 2.86 Å. Both Ba(2)-O(7) bond lengths are 2.85 Å. Both Ba(2)-O(9) bond lengths are 3.19 Å. There are two shorter (2.81 Å) and two longer (3.31 Å) Ba(2)-O(2) bond lengths. Nb(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted NbO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Nb(1)-O(1) bond length is 1.99 Å. The Nb(1)-O(3) bond length is 1.78 Å. The Nb(1)-O(4) bond length is 2.29 Å. The Nb(1)-O(5) bond length is 2.03 Å. The Nb(1)-O(6) bond length is 2.05 Å. The Nb(1)-O(7) bond length is 2.06 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(5), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-45°. The P(1)-O(2) bond length is 1.53 Å. The P(1)-O(5) bond length is 1.57 Å. The P(1)-O(7) bond length is 1.58 Å. The P(1)-O(8) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(1), one O(4), one O(6), and one O(9) atom to form PO4 tetrahedra that share corners with three equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 34-45°. The P(2)-O(1) bond length is 1.56 Å. The P(2)-O(4) bond length is 1.54 Å. The P(2)-O(6) bond length is 1.58 Å. The P(2)-O(9) bond length is 1.53 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Nb(1) and one P(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one P(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one Nb(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ba(2), one Nb(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ba(1), one Nb(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ba(1), one Nb(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ba(2), one Nb(1), and one P(1) atom. In the eighth O site, O(8) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one P(1) atom. In the ninth O site, O(9) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one P(2) atom.