Cs2CaP2O7 is Pb(Zr_(1-x)Ti_x)O3-derived structured and crystallizes in the monoclinic Cm space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(4), and four equivalent O(2) atoms. Ca(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form CaO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(5), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-26°. In the second P site, P(2) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-23°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Cs(1), one Ca(1), and one P(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Cs(1), two equivalent Cs(2), one Ca(1), and one P(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Cs(2), two equivalent Cs(1), one Ca(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Cs(2), one Ca(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Cs(1), one P(1), and one P(2) atom.
Cs2CaP2O7 is Pb(Zr_(1-x)Ti_x)O3-derived structured and crystallizes in the monoclinic Cm space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to one O(5), two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. The Cs(1)-O(5) bond length is 3.40 Å. Both Cs(1)-O(2) bond lengths are 3.62 Å. Both Cs(1)-O(3) bond lengths are 3.12 Å. There are two shorter (3.16 Å) and two longer (3.17 Å) Cs(1)-O(1) bond lengths. In the second Cs site, Cs(2) is bonded in a 7-coordinate geometry to one O(3), two equivalent O(4), and four equivalent O(2) atoms. The Cs(2)-O(3) bond length is 3.60 Å. Both Cs(2)-O(4) bond lengths are 3.19 Å. There are two shorter (3.12 Å) and two longer (3.14 Å) Cs(2)-O(2) bond lengths. Ca(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form CaO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Ca(1)-O(3) bond length is 2.45 Å. The Ca(1)-O(4) bond length is 2.33 Å. Both Ca(1)-O(1) bond lengths are 2.35 Å. Both Ca(1)-O(2) bond lengths are 2.42 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(5), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 16-26°. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(5) bond length is 1.63 Å. Both P(1)-O(1) bond lengths are 1.53 Å. In the second P site, P(2) is bonded to one O(4), one O(5), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-23°. The P(2)-O(4) bond length is 1.53 Å. The P(2)-O(5) bond length is 1.63 Å. Both P(2)-O(2) bond lengths are 1.53 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent Cs(1), one Ca(1), and one P(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Cs(1), two equivalent Cs(2), one Ca(1), and one P(2) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Cs(2), two equivalent Cs(1), one Ca(1), and one P(1) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to two equivalent Cs(2), one Ca(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to one Cs(1), one P(1), and one P(2) atom.