Ca5CAs3O12 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one C(1), one O(2), and four equivalent O(3) atoms. C(1) is bonded in a trigonal planar geometry to three equivalent Ca(2) atoms. As(1) is bonded in a tetrahedral geometry to one O(1), one O(2), and two equivalent O(3) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one As(1) atom. In the second O site, O(2) is bonded to one Ca(2), two equivalent Ca(1), and one As(1) atom to form distorted edge-sharing OCa3As tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one As(1) atom.
Ca5CAs3O12 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. All Ca(1)-O(1) bond lengths are 2.43 Å. All Ca(1)-O(2) bond lengths are 2.50 Å. All Ca(1)-O(3) bond lengths are 2.94 Å. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one C(1), one O(2), and four equivalent O(3) atoms. The Ca(2)-C(1) bond length is 2.59 Å. The Ca(2)-O(2) bond length is 2.36 Å. There are two shorter (2.35 Å) and two longer (2.52 Å) Ca(2)-O(3) bond lengths. C(1) is bonded in a trigonal planar geometry to three equivalent Ca(2) atoms. As(1) is bonded in a tetrahedral geometry to one O(1), one O(2), and two equivalent O(3) atoms. The As(1)-O(1) bond length is 1.71 Å. The As(1)-O(2) bond length is 1.74 Å. Both As(1)-O(3) bond lengths are 1.72 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one As(1) atom. In the second O site, O(2) is bonded to one Ca(2), two equivalent Ca(1), and one As(1) atom to form distorted edge-sharing OCa3As tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one As(1) atom.