CaB4O7 crystallizes in the orthorhombic Pmn2_1 space group. Ca(1) is bonded in a 9-coordinate geometry to one O(3), four equivalent O(1), and four equivalent O(2) atoms. There are two inequivalent B sites. In the first B site, B(1) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form corner-sharing BO4 tetrahedra. In the second B site, B(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing BO4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1), one B(1), and one B(2) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent Ca(1), one B(1), and one B(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and two equivalent B(2) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one B(2) and two equivalent B(1) atoms.
CaB4O7 crystallizes in the orthorhombic Pmn2_1 space group. Ca(1) is bonded in a 9-coordinate geometry to one O(3), four equivalent O(1), and four equivalent O(2) atoms. The Ca(1)-O(3) bond length is 2.48 Å. There are two shorter (2.43 Å) and two longer (2.85 Å) Ca(1)-O(1) bond lengths. There are two shorter (2.59 Å) and two longer (2.75 Å) Ca(1)-O(2) bond lengths. There are two inequivalent B sites. In the first B site, B(1) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form corner-sharing BO4 tetrahedra. The B(1)-O(1) bond length is 1.43 Å. The B(1)-O(2) bond length is 1.42 Å. There is one shorter (1.52 Å) and one longer (1.53 Å) B(1)-O(4) bond length. In the second B site, B(2) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing BO4 tetrahedra. The B(2)-O(1) bond length is 1.45 Å. The B(2)-O(2) bond length is 1.45 Å. The B(2)-O(3) bond length is 1.44 Å. The B(2)-O(4) bond length is 1.54 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Ca(1), one B(1), and one B(2) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to two equivalent Ca(1), one B(1), and one B(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and two equivalent B(2) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one B(2) and two equivalent B(1) atoms.