Cs3H(SeO4)2 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 6-coordinate geometry to one O(3), one O(6), two equivalent O(1), and two equivalent O(4) atoms. In the second Cs site, Cs(2) is bonded in a 10-coordinate geometry to one O(2), two equivalent O(1), three equivalent O(3), and four equivalent O(4) atoms. In the third Cs site, Cs(3) is bonded in a 10-coordinate geometry to one O(5), two equivalent O(4), three equivalent O(6), and four equivalent O(1) atoms. H(1) is bonded in a linear geometry to one O(2) and one O(5) atom. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a tetrahedral geometry to one O(2), one O(3), and two equivalent O(1) atoms. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(5), one O(6), and two equivalent O(4) atoms. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Cs(1), one Cs(2), two equivalent Cs(3), and one Se(1) atom. In the second O site, O(2) is bonded in a distorted water-like geometry to one Cs(2), one H(1), and one Se(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cs(1), three equivalent Cs(2), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Cs(1), one Cs(3), two equivalent Cs(2), and one Se(2) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Cs(3), one H(1), and one Se(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Cs(1), three equivalent Cs(3), and one Se(2) atom.
Cs3H(SeO4)2 crystallizes in the monoclinic P2_1/m space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 6-coordinate geometry to one O(3), one O(6), two equivalent O(1), and two equivalent O(4) atoms. The Cs(1)-O(3) bond length is 3.09 Å. The Cs(1)-O(6) bond length is 3.21 Å. Both Cs(1)-O(1) bond lengths are 3.21 Å. Both Cs(1)-O(4) bond lengths are 3.27 Å. In the second Cs site, Cs(2) is bonded in a 10-coordinate geometry to one O(2), two equivalent O(1), three equivalent O(3), and four equivalent O(4) atoms. The Cs(2)-O(2) bond length is 3.46 Å. Both Cs(2)-O(1) bond lengths are 3.27 Å. There are two shorter (3.40 Å) and one longer (3.53 Å) Cs(2)-O(3) bond length. There are two shorter (3.30 Å) and two longer (3.31 Å) Cs(2)-O(4) bond lengths. In the third Cs site, Cs(3) is bonded in a 10-coordinate geometry to one O(5), two equivalent O(4), three equivalent O(6), and four equivalent O(1) atoms. The Cs(3)-O(5) bond length is 3.45 Å. Both Cs(3)-O(4) bond lengths are 3.30 Å. There are two shorter (3.45 Å) and one longer (3.48 Å) Cs(3)-O(6) bond length. There are two shorter (3.20 Å) and two longer (3.27 Å) Cs(3)-O(1) bond lengths. H(1) is bonded in a linear geometry to one O(2) and one O(5) atom. The H(1)-O(2) bond length is 1.52 Å. The H(1)-O(5) bond length is 1.06 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a tetrahedral geometry to one O(2), one O(3), and two equivalent O(1) atoms. The Se(1)-O(2) bond length is 1.71 Å. The Se(1)-O(3) bond length is 1.67 Å. Both Se(1)-O(1) bond lengths are 1.68 Å. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(5), one O(6), and two equivalent O(4) atoms. The Se(2)-O(5) bond length is 1.78 Å. The Se(2)-O(6) bond length is 1.65 Å. Both Se(2)-O(4) bond lengths are 1.66 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Cs(1), one Cs(2), two equivalent Cs(3), and one Se(1) atom. In the second O site, O(2) is bonded in a distorted water-like geometry to one Cs(2), one H(1), and one Se(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cs(1), three equivalent Cs(2), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Cs(1), one Cs(3), two equivalent Cs(2), and one Se(2) atom. In the fifth O site, O(5) is bonded in a distorted water-like geometry to one Cs(3), one H(1), and one Se(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Cs(1), three equivalent Cs(3), and one Se(2) atom.