Na2CaTa(PO4)3 crystallizes in the monoclinic Cc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(4), one O(5), one O(7), and one O(9) atom. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to one O(10), one O(11), one O(12), one O(7), one O(8), and one O(9) atom. Ca(1) is bonded to one O(1), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form CaO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. Ta(1) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form TaO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(10), one O(5), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 18-44°. In the second P site, P(2) is bonded to one O(11), one O(2), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-36°. In the third P site, P(3) is bonded to one O(12), one O(3), one O(6), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-42°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Ca(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Ca(1), and one P(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ca(1) and one P(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Ta(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Na(1), one Ta(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ta(1) and one P(3) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Ca(1), and one P(2) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(2), one Ca(1), and one P(1) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ca(1), and one P(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal pyramidal geometry to one Na(1), one Na(2), one Ta(1), and one P(1) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Na(2), one Ta(1), and one P(2) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Na(2), one Ta(1), and one P(3) atom.
Na2CaTa(PO4)3 crystallizes in the monoclinic Cc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(4), one O(5), one O(7), and one O(9) atom. The Na(1)-O(1) bond length is 2.44 Å. The Na(1)-O(10) bond length is 2.40 Å. The Na(1)-O(2) bond length is 2.86 Å. The Na(1)-O(4) bond length is 2.93 Å. The Na(1)-O(5) bond length is 2.78 Å. The Na(1)-O(7) bond length is 2.50 Å. The Na(1)-O(9) bond length is 2.27 Å. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to one O(10), one O(11), one O(12), one O(7), one O(8), and one O(9) atom. The Na(2)-O(10) bond length is 2.64 Å. The Na(2)-O(11) bond length is 2.78 Å. The Na(2)-O(12) bond length is 2.65 Å. The Na(2)-O(7) bond length is 2.66 Å. The Na(2)-O(8) bond length is 2.52 Å. The Na(2)-O(9) bond length is 2.66 Å. Ca(1) is bonded to one O(1), one O(2), one O(3), one O(7), one O(8), and one O(9) atom to form CaO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. The Ca(1)-O(1) bond length is 2.25 Å. The Ca(1)-O(2) bond length is 2.14 Å. The Ca(1)-O(3) bond length is 2.14 Å. The Ca(1)-O(7) bond length is 2.29 Å. The Ca(1)-O(8) bond length is 2.23 Å. The Ca(1)-O(9) bond length is 2.29 Å. Ta(1) is bonded to one O(10), one O(11), one O(12), one O(4), one O(5), and one O(6) atom to form TaO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and corners with two equivalent P(3)O4 tetrahedra. The Ta(1)-O(10) bond length is 2.12 Å. The Ta(1)-O(11) bond length is 2.01 Å. The Ta(1)-O(12) bond length is 2.04 Å. The Ta(1)-O(4) bond length is 2.04 Å. The Ta(1)-O(5) bond length is 2.02 Å. The Ta(1)-O(6) bond length is 1.97 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(10), one O(5), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 18-44°. The P(1)-O(1) bond length is 1.50 Å. The P(1)-O(10) bond length is 1.60 Å. The P(1)-O(5) bond length is 1.64 Å. The P(1)-O(8) bond length is 1.50 Å. In the second P site, P(2) is bonded to one O(11), one O(2), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-36°. The P(2)-O(11) bond length is 1.59 Å. The P(2)-O(2) bond length is 1.49 Å. The P(2)-O(4) bond length is 1.63 Å. The P(2)-O(7) bond length is 1.52 Å. In the third P site, P(3) is bonded to one O(12), one O(3), one O(6), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-42°. The P(3)-O(12) bond length is 1.59 Å. The P(3)-O(3) bond length is 1.48 Å. The P(3)-O(6) bond length is 1.63 Å. The P(3)-O(9) bond length is 1.52 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Ca(1), and one P(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Ca(1), and one P(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ca(1) and one P(3) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Ta(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Na(1), one Ta(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ta(1) and one P(3) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Ca(1), and one P(2) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(2), one Ca(1), and one P(1) atom. In the ninth O site, O(9) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ca(1), and one P(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal pyramidal geometry to one Na(1), one Na(2), one Ta(1), and one P(1) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Na(2), one Ta(1), and one P(2) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Na(2), one Ta(1), and one P(3) atom.