TaOPO4 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(6), one O(7), two equivalent O(2), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent P(2)O4 tetrahedra. The corner-sharing octahedra are not tilted. In the second Ta site, Ta(2) is bonded to one O(5), one O(8), two equivalent O(1), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent P(1)O4 tetrahedra. The corner-sharing octahedra are not tilted. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(6), one O(8), and two equivalent O(3) atoms to form PO4 tetrahedra that share  a cornercorner with one Ta(1)O6 octahedra and corners with three equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-20°. In the second P site, P(2) is bonded to one O(5), one O(7), and two equivalent O(4) atoms to form PO4 tetrahedra that share  a cornercorner with one Ta(2)O6 octahedra and corners with three equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-26°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Ta(2) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the third O site, O(3) is bonded in a linear geometry to one Ta(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Ta(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Ta(2) and one P(2) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Ta(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ta(1) and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Ta(2) and one P(1) atom.
TaOPO4 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(6), one O(7), two equivalent O(2), and two equivalent O(4) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent P(2)O4 tetrahedra. The corner-sharing octahedra are not tilted. The Ta(1)-O(6) bond length is 1.97 Å. The Ta(1)-O(7) bond length is 1.98 Å. Both Ta(1)-O(2) bond lengths are 1.89 Å. Both Ta(1)-O(4) bond lengths are 2.03 Å. In the second Ta site, Ta(2) is bonded to one O(5), one O(8), two equivalent O(1), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(2)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with three equivalent P(1)O4 tetrahedra. The corner-sharing octahedra are not tilted. The Ta(2)-O(5) bond length is 1.96 Å. The Ta(2)-O(8) bond length is 1.98 Å. Both Ta(2)-O(1) bond lengths are 1.90 Å. Both Ta(2)-O(3) bond lengths are 2.03 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(6), one O(8), and two equivalent O(3) atoms to form PO4 tetrahedra that share  a cornercorner with one Ta(1)O6 octahedra and corners with three equivalent Ta(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 11-20°. The P(1)-O(6) bond length is 1.53 Å. The P(1)-O(8) bond length is 1.53 Å. Both P(1)-O(3) bond lengths are 1.52 Å. In the second P site, P(2) is bonded to one O(5), one O(7), and two equivalent O(4) atoms to form PO4 tetrahedra that share  a cornercorner with one Ta(2)O6 octahedra and corners with three equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-26°. The P(2)-O(5) bond length is 1.53 Å. The P(2)-O(7) bond length is 1.53 Å. Both P(2)-O(4) bond lengths are 1.52 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Ta(2) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the third O site, O(3) is bonded in a linear geometry to one Ta(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Ta(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Ta(2) and one P(2) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Ta(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Ta(1) and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Ta(2) and one P(1) atom.