CaB8O15 crystallizes in the monoclinic P2_1 space group. Ca(1) is bonded in a 9-coordinate geometry to one O(10), one O(14), one O(15), one O(2), one O(3), one O(4), one O(6), one O(7), and one O(9) atom. There are eight inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(5), one O(8), and one O(9) atom. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(15), one O(4), and one O(7) atom. In the third B site, B(3) is bonded to one O(1), one O(10), one O(5), and one O(7) atom to form corner-sharing BO4 tetrahedra. In the fourth B site, B(4) is bonded in a trigonal planar geometry to one O(10), one O(2), and one O(3) atom. In the fifth B site, B(5) is bonded to one O(1), one O(11), one O(2), and one O(3) atom to form corner-sharing BO4 tetrahedra. In the sixth B site, B(6) is bonded to one O(1), one O(12), one O(15), and one O(4) atom to form corner-sharing BO4 tetrahedra. In the seventh B site, B(7) is bonded in a trigonal planar geometry to one O(14), one O(6), and one O(8) atom. In the eighth B site, B(8) is bonded in a trigonal planar geometry to one O(11), one O(12), and one O(13) atom. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one B(3), one B(5), and one B(6) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(4), and one B(5) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Ca(1), one B(4), and one B(5) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(2), and one B(6) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one B(1) and one B(3) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(1) and one B(7) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(2), and one B(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one B(1) and one B(7) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Ca(1) and one B(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(3), and one B(4) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one B(5) and one B(8) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one B(6) and one B(8) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one B(8) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one B(7) atom. In the fifteenth O site, O(15) is bonded in a bent 120 degrees geometry to one Ca(1), one B(2), and one B(6) atom.
CaB8O15 crystallizes in the monoclinic P2_1 space group. Ca(1) is bonded in a 9-coordinate geometry to one O(10), one O(14), one O(15), one O(2), one O(3), one O(4), one O(6), one O(7), and one O(9) atom. The Ca(1)-O(10) bond length is 2.50 Å. The Ca(1)-O(14) bond length is 2.48 Å. The Ca(1)-O(15) bond length is 2.66 Å. The Ca(1)-O(2) bond length is 2.63 Å. The Ca(1)-O(3) bond length is 2.77 Å. The Ca(1)-O(4) bond length is 2.49 Å. The Ca(1)-O(6) bond length is 2.60 Å. The Ca(1)-O(7) bond length is 2.56 Å. The Ca(1)-O(9) bond length is 2.44 Å. There are eight inequivalent B sites. In the first B site, B(1) is bonded in a trigonal planar geometry to one O(5), one O(8), and one O(9) atom. The B(1)-O(5) bond length is 1.34 Å. The B(1)-O(8) bond length is 1.41 Å. The B(1)-O(9) bond length is 1.36 Å. In the second B site, B(2) is bonded in a trigonal planar geometry to one O(15), one O(4), and one O(7) atom. The B(2)-O(15) bond length is 1.38 Å. The B(2)-O(4) bond length is 1.37 Å. The B(2)-O(7) bond length is 1.36 Å. In the third B site, B(3) is bonded to one O(1), one O(10), one O(5), and one O(7) atom to form corner-sharing BO4 tetrahedra. The B(3)-O(1) bond length is 1.53 Å. The B(3)-O(10) bond length is 1.47 Å. The B(3)-O(5) bond length is 1.46 Å. The B(3)-O(7) bond length is 1.45 Å. In the fourth B site, B(4) is bonded in a trigonal planar geometry to one O(10), one O(2), and one O(3) atom. The B(4)-O(10) bond length is 1.37 Å. The B(4)-O(2) bond length is 1.38 Å. The B(4)-O(3) bond length is 1.37 Å. In the fifth B site, B(5) is bonded to one O(1), one O(11), one O(2), and one O(3) atom to form corner-sharing BO4 tetrahedra. The B(5)-O(1) bond length is 1.53 Å. The B(5)-O(11) bond length is 1.47 Å. The B(5)-O(2) bond length is 1.46 Å. The B(5)-O(3) bond length is 1.46 Å. In the sixth B site, B(6) is bonded to one O(1), one O(12), one O(15), and one O(4) atom to form corner-sharing BO4 tetrahedra. The B(6)-O(1) bond length is 1.53 Å. The B(6)-O(12) bond length is 1.48 Å. The B(6)-O(15) bond length is 1.46 Å. The B(6)-O(4) bond length is 1.45 Å. In the seventh B site, B(7) is bonded in a trigonal planar geometry to one O(14), one O(6), and one O(8) atom. The B(7)-O(14) bond length is 1.35 Å. The B(7)-O(6) bond length is 1.36 Å. The B(7)-O(8) bond length is 1.41 Å. In the eighth B site, B(8) is bonded in a trigonal planar geometry to one O(11), one O(12), and one O(13) atom. The B(8)-O(11) bond length is 1.38 Å. The B(8)-O(12) bond length is 1.38 Å. The B(8)-O(13) bond length is 1.37 Å. There are fifteen inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one B(3), one B(5), and one B(6) atom. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(4), and one B(5) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Ca(1), one B(4), and one B(5) atom. In the fourth O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(2), and one B(6) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one B(1) and one B(3) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(1) and one B(7) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(2), and one B(3) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one B(1) and one B(7) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Ca(1) and one B(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one B(3), and one B(4) atom. In the eleventh O site, O(11) is bonded in a bent 120 degrees geometry to one B(5) and one B(8) atom. In the twelfth O site, O(12) is bonded in a bent 120 degrees geometry to one B(6) and one B(8) atom. In the thirteenth O site, O(13) is bonded in a single-bond geometry to one B(8) atom. In the fourteenth O site, O(14) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one B(7) atom. In the fifteenth O site, O(15) is bonded in a bent 120 degrees geometry to one Ca(1), one B(2), and one B(6) atom.