K2Ca2(CO3)3 crystallizes in the trigonal R3 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to three equivalent O(2) and three equivalent O(4) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(1), one O(6), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(3), one O(5), two equivalent O(2), and two equivalent O(6) atoms to form distorted edge-sharing CaO7 pentagonal bipyramids. In the second Ca site, Ca(2) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(4), and three equivalent O(5) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one O(4), one O(5), and one O(6) atom. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(2), one Ca(1), one Ca(2), and one C(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1), two equivalent Ca(1), and one C(2) atom. In the third O site, O(3) is bonded to two equivalent K(2), one Ca(1), and one C(2) atom to form distorted corner-sharing OK2CaC tetrahedra. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), one Ca(2), and one C(1) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ca(1), one Ca(2), and one C(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one K(2), two equivalent Ca(1), and one C(1) atom.
K2Ca2(CO3)3 crystallizes in the trigonal R3 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to three equivalent O(2) and three equivalent O(4) atoms. All K(1)-O(2) bond lengths are 2.73 Å. All K(1)-O(4) bond lengths are 2.73 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(1), one O(6), two equivalent O(3), and two equivalent O(4) atoms. The K(2)-O(1) bond length is 2.80 Å. The K(2)-O(6) bond length is 2.81 Å. There is one shorter (2.68 Å) and one longer (2.78 Å) K(2)-O(3) bond length. There is one shorter (2.85 Å) and one longer (2.99 Å) K(2)-O(4) bond length. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(3), one O(5), two equivalent O(2), and two equivalent O(6) atoms to form distorted edge-sharing CaO7 pentagonal bipyramids. The Ca(1)-O(1) bond length is 2.45 Å. The Ca(1)-O(3) bond length is 2.40 Å. The Ca(1)-O(5) bond length is 2.40 Å. There is one shorter (2.40 Å) and one longer (2.59 Å) Ca(1)-O(2) bond length. There is one shorter (2.37 Å) and one longer (2.39 Å) Ca(1)-O(6) bond length. In the second Ca site, Ca(2) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(4), and three equivalent O(5) atoms. All Ca(2)-O(1) bond lengths are 2.41 Å. All Ca(2)-O(4) bond lengths are 2.46 Å. All Ca(2)-O(5) bond lengths are 2.56 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to one O(4), one O(5), and one O(6) atom. The C(1)-O(4) bond length is 1.29 Å. The C(1)-O(5) bond length is 1.29 Å. The C(1)-O(6) bond length is 1.30 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to one O(1), one O(2), and one O(3) atom. The C(2)-O(1) bond length is 1.30 Å. The C(2)-O(2) bond length is 1.29 Å. The C(2)-O(3) bond length is 1.29 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(2), one Ca(1), one Ca(2), and one C(2) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(1), two equivalent Ca(1), and one C(2) atom. In the third O site, O(3) is bonded to two equivalent K(2), one Ca(1), and one C(2) atom to form distorted corner-sharing OK2CaC tetrahedra. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one K(1), two equivalent K(2), one Ca(2), and one C(1) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to one Ca(1), one Ca(2), and one C(1) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one K(2), two equivalent Ca(1), and one C(1) atom.