Ca2B2O5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(3), two equivalent O(2), and three equivalent O(5) atoms to form a mixture of distorted corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles range from 63-74°. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(2), one O(4), two equivalent O(3), and three equivalent O(1) atoms. There are two inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(3), one O(4), and one O(5) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(4) atom. There are five inequivalent O sites. In the first O site, O(5) is bonded to three equivalent Ca(1) and one B(1) atom to form distorted corner-sharing OCa3B tetrahedra. In the second O site, O(1) is bonded in a 4-coordinate geometry to three equivalent Ca(2) and one B(2) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one B(2) atom. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one B(1) atom. In the fifth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(2), one B(1), and one B(2) atom.
Ca2B2O5 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(3), two equivalent O(2), and three equivalent O(5) atoms to form a mixture of distorted corner and edge-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles range from 63-74°. The Ca(1)-O(3) bond length is 2.35 Å. There is one shorter (2.32 Å) and one longer (2.34 Å) Ca(1)-O(2) bond length. There are a spread of Ca(1)-O(5) bond distances ranging from 2.38-2.41 Å. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(2), one O(4), two equivalent O(3), and three equivalent O(1) atoms. The Ca(2)-O(2) bond length is 2.38 Å. The Ca(2)-O(4) bond length is 2.47 Å. There is one shorter (2.42 Å) and one longer (2.52 Å) Ca(2)-O(3) bond length. There are a spread of Ca(2)-O(1) bond distances ranging from 2.30-2.61 Å. There are two inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(3), one O(4), and one O(5) atom. The B(1)-O(3) bond length is 1.36 Å. The B(1)-O(4) bond length is 1.43 Å. The B(1)-O(5) bond length is 1.36 Å. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(4) atom. The B(2)-O(1) bond length is 1.36 Å. The B(2)-O(2) bond length is 1.36 Å. The B(2)-O(4) bond length is 1.42 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded to three equivalent Ca(1) and one B(1) atom to form distorted corner-sharing OCa3B tetrahedra. In the second O site, O(1) is bonded in a 4-coordinate geometry to three equivalent Ca(2) and one B(2) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one B(2) atom. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one B(1) atom. In the fifth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(2), one B(1), and one B(2) atom.