CaTiAsO5 crystallizes in the monoclinic P2_1 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(3), one O(4), one O(5), one O(9), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(3), one O(4), one O(6), and one O(8) atom. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(10), one O(2), one O(5), one O(8), and one O(9) atom to form distorted TiO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra and edges with two equivalent Ti(2)O6 octahedra. In the second Ti site, Ti(2) is bonded to one O(1), one O(10), one O(2), one O(6), one O(7), and one O(9) atom to form TiO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra and edges with two equivalent Ti(1)O6 octahedra. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 3-coordinate geometry to one O(1), one O(3), one O(5), and one O(7) atom. In the second As site, As(2) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-59°. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), one Ti(1), one Ti(2), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ti(1), one Ti(2), and one As(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(2), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Ca(1), one Ti(1), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(2), one Ti(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ti(2), and one As(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(2), one Ti(1), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ti(1), and one Ti(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one Ca(2), one Ti(1), and one Ti(2) atom.
CaTiAsO5 crystallizes in the monoclinic P2_1 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(3), one O(4), one O(5), one O(9), and two equivalent O(7) atoms. The Ca(1)-O(3) bond length is 2.43 Å. The Ca(1)-O(4) bond length is 2.36 Å. The Ca(1)-O(5) bond length is 2.44 Å. The Ca(1)-O(9) bond length is 2.46 Å. There is one shorter (2.46 Å) and one longer (2.82 Å) Ca(1)-O(7) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(3), one O(4), one O(6), and one O(8) atom. The Ca(2)-O(1) bond length is 2.40 Å. The Ca(2)-O(10) bond length is 2.49 Å. The Ca(2)-O(3) bond length is 2.37 Å. The Ca(2)-O(4) bond length is 2.55 Å. The Ca(2)-O(6) bond length is 2.45 Å. The Ca(2)-O(8) bond length is 2.55 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(10), one O(2), one O(5), one O(8), and one O(9) atom to form distorted TiO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra and edges with two equivalent Ti(2)O6 octahedra. The Ti(1)-O(1) bond length is 1.91 Å. The Ti(1)-O(10) bond length is 1.81 Å. The Ti(1)-O(2) bond length is 2.19 Å. The Ti(1)-O(5) bond length is 1.93 Å. The Ti(1)-O(8) bond length is 2.09 Å. The Ti(1)-O(9) bond length is 2.08 Å. In the second Ti site, Ti(2) is bonded to one O(1), one O(10), one O(2), one O(6), one O(7), and one O(9) atom to form TiO6 octahedra that share corners with two equivalent As(2)O4 tetrahedra and edges with two equivalent Ti(1)O6 octahedra. The Ti(2)-O(1) bond length is 1.88 Å. The Ti(2)-O(10) bond length is 2.09 Å. The Ti(2)-O(2) bond length is 2.11 Å. The Ti(2)-O(6) bond length is 2.15 Å. The Ti(2)-O(7) bond length is 1.94 Å. The Ti(2)-O(9) bond length is 1.82 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 3-coordinate geometry to one O(1), one O(3), one O(5), and one O(7) atom. The As(1)-O(1) bond length is 2.50 Å. The As(1)-O(3) bond length is 1.77 Å. The As(1)-O(5) bond length is 1.88 Å. The As(1)-O(7) bond length is 1.88 Å. In the second As site, As(2) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form AsO4 tetrahedra that share corners with two equivalent Ti(1)O6 octahedra and corners with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-59°. The As(2)-O(2) bond length is 1.74 Å. The As(2)-O(4) bond length is 1.70 Å. The As(2)-O(6) bond length is 1.73 Å. The As(2)-O(8) bond length is 1.72 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), one Ti(1), one Ti(2), and one As(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ti(1), one Ti(2), and one As(2) atom. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(2), and one As(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one As(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Ca(1), one Ti(1), and one As(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Ca(2), one Ti(2), and one As(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ti(2), and one As(1) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(2), one Ti(1), and one As(2) atom. In the ninth O site, O(9) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ti(1), and one Ti(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal non-coplanar geometry to one Ca(2), one Ti(1), and one Ti(2) atom.