Na2Ca(CO3)2 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 9-coordinate geometry to three equivalent O(1) and six equivalent O(2) atoms. In the second Na site, Na(2) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(2) atoms. Ca(1) is bonded in a 11-coordinate geometry to two equivalent C(2), three equivalent O(2), and six 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 three equivalent O(1) atoms. In the second C site, C(2) is bonded in a trigonal planar geometry to two equivalent Ca(1) and three equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), two equivalent Ca(1), and one C(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Na(2), two equivalent Na(1), one Ca(1), and one C(2) atom.
Na2Ca(CO3)2 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 9-coordinate geometry to three equivalent O(1) and six equivalent O(2) atoms. All Na(1)-O(1) bond lengths are 2.78 Å. All Na(1)-O(2) bond lengths are 2.68 Å. In the second Na site, Na(2) is bonded in an octahedral geometry to three equivalent O(1) and three equivalent O(2) atoms. All Na(2)-O(1) bond lengths are 2.36 Å. All Na(2)-O(2) bond lengths are 2.22 Å. Ca(1) is bonded in a 11-coordinate geometry to two equivalent C(2), three equivalent O(2), and six equivalent O(1) atoms. There is one shorter (2.58 Å) and one longer (3.19 Å) Ca(1)-C(2) bond length. All Ca(1)-O(2) bond lengths are 2.84 Å. All Ca(1)-O(1) bond lengths are 2.63 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded in a trigonal planar geometry to three equivalent O(1) atoms. All C(1)-O(1) bond lengths are 1.30 Å. In the second C site, C(2) is bonded in a trigonal planar geometry to two equivalent Ca(1) and three equivalent O(2) atoms. All C(2)-O(2) bond lengths are 1.30 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), two equivalent Ca(1), and one C(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Na(2), two equivalent Na(1), one Ca(1), and one C(2) atom.