Ca3Co(SeO3)4 crystallizes in the tetragonal I4_1/a space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. In the second Ca site, Ca(2) is bonded in a distorted hexagonal bipyramidal geometry to four equivalent O(1) and four equivalent O(3) atoms. Co(1) is bonded in a tetrahedral geometry to four equivalent O(2) atoms. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Se(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Co(1), and one Se(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), and one Se(1) atom.
Ca3Co(SeO3)4 crystallizes in the tetragonal I4_1/a space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. Both Ca(1)-O(2) bond lengths are 2.58 Å. Both Ca(1)-O(3) bond lengths are 2.34 Å. There are two shorter (2.38 Å) and two longer (2.95 Å) Ca(1)-O(1) bond lengths. In the second Ca site, Ca(2) is bonded in a distorted hexagonal bipyramidal geometry to four equivalent O(1) and four equivalent O(3) atoms. All Ca(2)-O(1) bond lengths are 2.63 Å. All Ca(2)-O(3) bond lengths are 2.42 Å. Co(1) is bonded in a tetrahedral geometry to four equivalent O(2) atoms. All Co(1)-O(2) bond lengths are 1.99 Å. Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.71 Å. The Se(1)-O(2) bond length is 1.76 Å. The Se(1)-O(3) bond length is 1.72 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Se(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Ca(1), one Co(1), and one Se(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), and one Se(1) atom.