CaCO3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted octahedral geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(4) atom. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(3) atoms. There are five inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one C(2) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one C(1) atom. In the third O site, O(5) is bonded in a trigonal planar geometry to two equivalent Ca(2) and one C(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ca(2) and one C(1) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one C(1) atom.
CaCO3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted octahedral geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Ca(1)-O(2) bond lengths are 2.39 Å. Both Ca(1)-O(3) bond lengths are 2.42 Å. Both Ca(1)-O(4) bond lengths are 2.32 Å. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms. The Ca(2)-O(2) bond length is 2.40 Å. The Ca(2)-O(3) bond length is 2.40 Å. The Ca(2)-O(4) bond length is 2.32 Å. The Ca(2)-O(5) bond length is 2.35 Å. There is one shorter (2.34 Å) and one longer (2.37 Å) Ca(2)-O(1) bond length. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(4) atom. The C(1)-O(1) bond length is 1.29 Å. The C(1)-O(2) bond length is 1.29 Å. The C(1)-O(4) bond length is 1.29 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(5) and two equivalent O(3) atoms. The C(2)-O(5) bond length is 1.29 Å. Both C(2)-O(3) bond lengths are 1.29 Å. There are five inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one C(2) atom. In the second O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one Ca(2), and one C(1) atom. In the third O site, O(5) is bonded in a trigonal planar geometry to two equivalent Ca(2) and one C(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ca(2) and one C(1) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Ca(2), and one C(1) atom.