Ca3Ti3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), one O(5), one O(7), and two equivalent O(3) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(8) atom to form distorted TiO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra. In the second Ti site, Ti(2) is bonded in a distorted square co-planar geometry to two equivalent O(5) and two equivalent O(7) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with three equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-60°. In the second As site, As(2) is bonded in a 3-coordinate geometry to one O(3), one O(5), and one O(7) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Ti(1), one Ti(2), and one As(2) atom. In the second O site, O(8) is bonded in a distorted trigonal planar geometry to one Ca(2), one Ti(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ti(1), and one As(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to one Ca(2) and one Ti(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one As(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ti(1), and one As(1) atom. In the seventh O site, O(5) is bonded to one Ca(1), one Ti(1), one Ti(2), and one As(2) atom to form corner-sharing OCaTi2As tetrahedra. In the eighth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(2) and one As(1) atom.
Ca3Ti3(AsO4)4 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to one O(1), one O(4), one O(5), one O(7), and two equivalent O(3) atoms. The Ca(1)-O(1) bond length is 2.37 Å. The Ca(1)-O(4) bond length is 2.47 Å. The Ca(1)-O(5) bond length is 2.39 Å. The Ca(1)-O(7) bond length is 2.57 Å. There is one shorter (2.29 Å) and one longer (2.39 Å) Ca(1)-O(3) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms. Both Ca(2)-O(2) bond lengths are 2.31 Å. Both Ca(2)-O(6) bond lengths are 2.42 Å. Both Ca(2)-O(8) bond lengths are 2.50 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(8) atom to form distorted TiO6 octahedra that share corners with three equivalent As(1)O4 tetrahedra. The Ti(1)-O(1) bond length is 2.17 Å. The Ti(1)-O(2) bond length is 1.73 Å. The Ti(1)-O(4) bond length is 1.99 Å. The Ti(1)-O(5) bond length is 2.11 Å. The Ti(1)-O(7) bond length is 2.05 Å. The Ti(1)-O(8) bond length is 2.19 Å. In the second Ti site, Ti(2) is bonded in a distorted square co-planar geometry to two equivalent O(5) and two equivalent O(7) atoms. Both Ti(2)-O(5) bond lengths are 2.14 Å. Both Ti(2)-O(7) bond lengths are 2.08 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded to one O(1), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with three equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-60°. The As(1)-O(1) bond length is 1.74 Å. The As(1)-O(4) bond length is 1.74 Å. The As(1)-O(6) bond length is 1.70 Å. The As(1)-O(8) bond length is 1.75 Å. In the second As site, As(2) is bonded in a 3-coordinate geometry to one O(3), one O(5), and one O(7) atom. The As(2)-O(3) bond length is 1.74 Å. The As(2)-O(5) bond length is 1.89 Å. The As(2)-O(7) bond length is 1.96 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), one Ti(1), one Ti(2), and one As(2) atom. In the second O site, O(8) is bonded in a distorted trigonal planar geometry to one Ca(2), one Ti(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ti(1), and one As(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to one Ca(2) and one Ti(1) atom. In the fifth O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one As(2) atom. In the sixth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ti(1), and one As(1) atom. In the seventh O site, O(5) is bonded to one Ca(1), one Ti(1), one Ti(2), and one As(2) atom to form corner-sharing OCaTi2As tetrahedra. In the eighth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(2) and one As(1) atom.