Cs3H(SeO4)2 crystallizes in the monoclinic Cc space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to one O(2), one O(4), one O(6), two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(5), two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms. In the third Cs site, Cs(3) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom. H(1) is bonded in a linear geometry to one O(5) and one O(6) atom. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a tetrahedral geometry to one O(1), one O(3), one O(5), and one O(7) atom. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(2), one O(4), one O(6), and one O(8) atom. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a distorted water-like geometry to one Cs(2), one H(1), and one Se(1) atom. In the second O site, O(6) is bonded in a 2-coordinate geometry to one Cs(1), one H(1), and one Se(2) atom. In the third O site, O(7) is bonded in a distorted single-bond geometry to one Cs(3), two equivalent Cs(1), and one Se(1) atom. In the fourth O site, O(8) is bonded in a distorted single-bond geometry to one Cs(3), two equivalent Cs(2), and one Se(2) atom. In the fifth O site, O(1) is bonded in a distorted single-bond geometry to one Cs(2), one Cs(3), two equivalent Cs(1), and one Se(1) atom. In the sixth O site, O(2) 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 seventh O site, O(3) is bonded in a distorted single-bond geometry to one Cs(2), one Cs(3), two equivalent Cs(1), and one Se(1) atom. In the eighth 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.
Cs3H(SeO4)2 crystallizes in the monoclinic Cc space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 9-coordinate geometry to one O(2), one O(4), one O(6), two equivalent O(1), two equivalent O(3), and two equivalent O(7) atoms. The Cs(1)-O(2) bond length is 3.27 Å. The Cs(1)-O(4) bond length is 3.18 Å. The Cs(1)-O(6) bond length is 3.29 Å. There is one shorter (3.27 Å) and one longer (3.38 Å) Cs(1)-O(1) bond length. There is one shorter (3.36 Å) and one longer (3.41 Å) Cs(1)-O(3) bond length. There is one shorter (3.28 Å) and one longer (3.42 Å) Cs(1)-O(7) bond length. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(5), two equivalent O(2), two equivalent O(4), and two equivalent O(8) atoms. The Cs(2)-O(1) bond length is 3.24 Å. The Cs(2)-O(3) bond length is 3.12 Å. The Cs(2)-O(5) bond length is 3.36 Å. There is one shorter (3.30 Å) and one longer (3.36 Å) Cs(2)-O(2) bond length. There is one shorter (3.34 Å) and one longer (3.45 Å) Cs(2)-O(4) bond length. There is one shorter (3.30 Å) and one longer (3.44 Å) Cs(2)-O(8) bond length. In the third Cs site, Cs(3) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom. The Cs(3)-O(1) bond length is 3.19 Å. The Cs(3)-O(2) bond length is 3.24 Å. The Cs(3)-O(3) bond length is 3.27 Å. The Cs(3)-O(4) bond length is 3.28 Å. The Cs(3)-O(7) bond length is 3.06 Å. The Cs(3)-O(8) bond length is 3.07 Å. H(1) is bonded in a linear geometry to one O(5) and one O(6) atom. The H(1)-O(5) bond length is 1.45 Å. The H(1)-O(6) bond length is 1.08 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a tetrahedral geometry to one O(1), one O(3), one O(5), and one O(7) atom. The Se(1)-O(1) bond length is 1.68 Å. The Se(1)-O(3) bond length is 1.67 Å. The Se(1)-O(5) bond length is 1.71 Å. The Se(1)-O(7) bond length is 1.67 Å. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(2), one O(4), one O(6), and one O(8) atom. The Se(2)-O(2) bond length is 1.66 Å. The Se(2)-O(4) bond length is 1.66 Å. The Se(2)-O(6) bond length is 1.77 Å. The Se(2)-O(8) bond length is 1.65 Å. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a distorted water-like geometry to one Cs(2), one H(1), and one Se(1) atom. In the second O site, O(6) is bonded in a 2-coordinate geometry to one Cs(1), one H(1), and one Se(2) atom. In the third O site, O(7) is bonded in a distorted single-bond geometry to one Cs(3), two equivalent Cs(1), and one Se(1) atom. In the fourth O site, O(8) is bonded in a distorted single-bond geometry to one Cs(3), two equivalent Cs(2), and one Se(2) atom. In the fifth O site, O(1) is bonded in a distorted single-bond geometry to one Cs(2), one Cs(3), two equivalent Cs(1), and one Se(1) atom. In the sixth O site, O(2) 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 seventh O site, O(3) is bonded in a distorted single-bond geometry to one Cs(2), one Cs(3), two equivalent Cs(1), and one Se(1) atom. In the eighth 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.