Ca2Bi2O5 crystallizes in the orthorhombic Pbam space group. Ca(1) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(2), and three equivalent O(3) atoms. Bi(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted corner-sharing BiO5 square pyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ca(1) and two equivalent Bi(1) atoms to form distorted OCa4Bi2 octahedra that share corners with eight equivalent O(2)Ca2Bi2 tetrahedra, corners with four equivalent O(3)Ca3Bi2 trigonal bipyramids, edges with two equivalent O(1)Ca4Bi2 octahedra, edges with two equivalent O(2)Ca2Bi2 tetrahedra, and faces with four equivalent O(3)Ca3Bi2 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Ca(1) and two equivalent Bi(1) atoms to form distorted OCa2Bi2 tetrahedra that share corners with four equivalent O(1)Ca4Bi2 octahedra, corners with four equivalent O(2)Ca2Bi2 tetrahedra, corners with six equivalent O(3)Ca3Bi2 trigonal bipyramids,  an edgeedge with one O(1)Ca4Bi2 octahedra, and edges with two equivalent O(3)Ca3Bi2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 12-80°. In the third O site, O(3) is bonded to three equivalent Ca(1) and two equivalent Bi(1) atoms to form distorted OCa3Bi2 trigonal bipyramids that share corners with two equivalent O(1)Ca4Bi2 octahedra, corners with six equivalent O(2)Ca2Bi2 tetrahedra, corners with six equivalent O(3)Ca3Bi2 trigonal bipyramids, edges with two equivalent O(2)Ca2Bi2 tetrahedra,  an edgeedge with one O(3)Ca3Bi2 trigonal bipyramid, and faces with two equivalent O(1)Ca4Bi2 octahedra. The corner-sharing octahedral tilt angles are 55°.
Ca2Bi2O5 crystallizes in the orthorhombic Pbam space group. Ca(1) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(2), and three equivalent O(3) atoms. Both Ca(1)-O(1) bond lengths are 2.76 Å. Both Ca(1)-O(2) bond lengths are 2.59 Å. There are a spread of Ca(1)-O(3) bond distances ranging from 2.36-2.83 Å. Bi(1) is bonded to one O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted corner-sharing BiO5 square pyramids. The Bi(1)-O(1) bond length is 2.23 Å. There is one shorter (2.14 Å) and one longer (2.64 Å) Bi(1)-O(2) bond length. Both Bi(1)-O(3) bond lengths are 2.28 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Ca(1) and two equivalent Bi(1) atoms to form distorted OCa4Bi2 octahedra that share corners with eight equivalent O(2)Ca2Bi2 tetrahedra, corners with four equivalent O(3)Ca3Bi2 trigonal bipyramids, edges with two equivalent O(1)Ca4Bi2 octahedra, edges with two equivalent O(2)Ca2Bi2 tetrahedra, and faces with four equivalent O(3)Ca3Bi2 trigonal bipyramids. In the second O site, O(2) is bonded to two equivalent Ca(1) and two equivalent Bi(1) atoms to form distorted OCa2Bi2 tetrahedra that share corners with four equivalent O(1)Ca4Bi2 octahedra, corners with four equivalent O(2)Ca2Bi2 tetrahedra, corners with six equivalent O(3)Ca3Bi2 trigonal bipyramids,  an edgeedge with one O(1)Ca4Bi2 octahedra, and edges with two equivalent O(3)Ca3Bi2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 12-80°. In the third O site, O(3) is bonded to three equivalent Ca(1) and two equivalent Bi(1) atoms to form distorted OCa3Bi2 trigonal bipyramids that share corners with two equivalent O(1)Ca4Bi2 octahedra, corners with six equivalent O(2)Ca2Bi2 tetrahedra, corners with six equivalent O(3)Ca3Bi2 trigonal bipyramids, edges with two equivalent O(2)Ca2Bi2 tetrahedra,  an edgeedge with one O(3)Ca3Bi2 trigonal bipyramid, and faces with two equivalent O(1)Ca4Bi2 octahedra. The corner-sharing octahedral tilt angles are 55°.