K4CO4 crystallizes in the monoclinic Cm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the second K site, K(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(3) atoms. C(1) is bonded in a tetrahedral geometry to one O(1), one O(3), and two equivalent O(2) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent K(1), two equivalent K(2), and one C(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one C(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to two equivalent K(1), four equivalent K(2), and one C(1) atom.
K4CO4 crystallizes in the monoclinic Cm space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. The K(1)-O(1) bond length is 2.61 Å. The K(1)-O(3) bond length is 3.12 Å. There is one shorter (2.56 Å) and one longer (2.60 Å) K(1)-O(2) bond length. In the second K site, K(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), and two equivalent O(3) atoms. The K(2)-O(1) bond length is 2.53 Å. The K(2)-O(2) bond length is 2.53 Å. There is one shorter (2.82 Å) and one longer (2.85 Å) K(2)-O(3) bond length. C(1) is bonded in a tetrahedral geometry to one O(1), one O(3), and two equivalent O(2) atoms. The C(1)-O(1) bond length is 1.42 Å. The C(1)-O(3) bond length is 1.51 Å. Both C(1)-O(2) bond lengths are 1.41 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to two equivalent K(1), two equivalent K(2), and one C(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one C(1) atom. In the third O site, O(3) is bonded in a single-bond geometry to two equivalent K(1), four equivalent K(2), and one C(1) atom.