Ca2Ti2O5 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 7-coordinate geometry to one O(1), one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(5) atoms. In the second Ti site, Ti(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 26°. In the third Ti site, Ti(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 26°. In the fourth Ti site, Ti(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(3), and one Ti(4) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Ti(2), and one Ti(3) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Ti(2), and one Ti(4) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), one Ti(1), and one Ti(3) atom to form distorted corner-sharing OCa3Ti2 trigonal bipyramids.
Ca2Ti2O5 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 7-coordinate geometry to one O(1), one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms. The Ca(1)-O(1) bond length is 2.46 Å. The Ca(1)-O(2) bond length is 2.34 Å. The Ca(1)-O(3) bond length is 2.67 Å. There is one shorter (2.38 Å) and one longer (2.74 Å) Ca(1)-O(4) bond length. There is one shorter (2.45 Å) and one longer (2.62 Å) Ca(1)-O(5) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), and two equivalent O(3) atoms. The Ca(2)-O(1) bond length is 2.43 Å. The Ca(2)-O(2) bond length is 2.45 Å. The Ca(2)-O(4) bond length is 2.54 Å. The Ca(2)-O(5) bond length is 2.61 Å. There is one shorter (2.42 Å) and one longer (2.67 Å) Ca(2)-O(3) bond length. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a square co-planar geometry to two equivalent O(2) and two equivalent O(5) atoms. Both Ti(1)-O(2) bond lengths are 1.94 Å. Both Ti(1)-O(5) bond lengths are 1.95 Å. In the second Ti site, Ti(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 26°. Both Ti(2)-O(2) bond lengths are 2.02 Å. Both Ti(2)-O(3) bond lengths are 1.95 Å. Both Ti(2)-O(4) bond lengths are 2.02 Å. In the third Ti site, Ti(3) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 26°. Both Ti(3)-O(1) bond lengths are 2.01 Å. Both Ti(3)-O(3) bond lengths are 1.95 Å. Both Ti(3)-O(5) bond lengths are 2.02 Å. In the fourth Ti site, Ti(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(4) atoms. Both Ti(4)-O(1) bond lengths are 1.94 Å. Both Ti(4)-O(4) bond lengths are 1.95 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(3), and one Ti(4) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Ca(1), two equivalent Ca(2), one Ti(2), and one Ti(3) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Ca(2), two equivalent Ca(1), one Ti(2), and one Ti(4) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), one Ti(1), and one Ti(3) atom to form distorted corner-sharing OCa3Ti2 trigonal bipyramids.