CaH4Se2O7 crystallizes in the triclinic P-1 space group. Ca(1) is bonded in a 8-coordinate geometry to one O(3), one O(4), one O(5), one O(6), two equivalent O(1), and two equivalent O(2) atoms. There are four inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to one O(3) and one O(7) atom. In the second H site, H(2) is bonded in a distorted linear geometry to one O(5) and one O(6) atom. In the third H site, H(3) is bonded in a single-bond geometry to one O(4) and one O(7) atom. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(7) atom. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ca(1) and one Se(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one H(1), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one H(3), and one Se(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one H(2), and one Se(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(1), one H(2), and one Se(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one H(1), one H(3), and one H(4) atom.
CaH4Se2O7 crystallizes in the triclinic P-1 space group. Ca(1) is bonded in a 8-coordinate geometry to one O(3), one O(4), one O(5), one O(6), two equivalent O(1), and two equivalent O(2) atoms. The Ca(1)-O(3) bond length is 2.44 Å. The Ca(1)-O(4) bond length is 2.51 Å. The Ca(1)-O(5) bond length is 2.56 Å. The Ca(1)-O(6) bond length is 2.49 Å. There is one shorter (2.43 Å) and one longer (2.62 Å) Ca(1)-O(1) bond length. There is one shorter (2.41 Å) and one longer (2.49 Å) Ca(1)-O(2) bond length. There are four inequivalent H sites. In the first H site, H(1) is bonded in a linear geometry to one O(3) and one O(7) atom. The H(1)-O(3) bond length is 1.05 Å. The H(1)-O(7) bond length is 1.55 Å. In the second H site, H(2) is bonded in a distorted linear geometry to one O(5) and one O(6) atom. The H(2)-O(5) bond length is 1.65 Å. The H(2)-O(6) bond length is 1.02 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(4) and one O(7) atom. The H(3)-O(4) bond length is 1.74 Å. The H(3)-O(7) bond length is 1.00 Å. In the fourth H site, H(4) is bonded in a single-bond geometry to one O(7) atom. The H(4)-O(7) bond length is 0.99 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a trigonal non-coplanar geometry to one O(1), one O(2), and one O(3) atom. The Se(1)-O(1) bond length is 1.70 Å. The Se(1)-O(2) bond length is 1.69 Å. The Se(1)-O(3) bond length is 1.83 Å. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one O(4), one O(5), and one O(6) atom. The Se(2)-O(4) bond length is 1.71 Å. The Se(2)-O(5) bond length is 1.73 Å. The Se(2)-O(6) bond length is 1.83 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Ca(1) and one Se(1) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Ca(1) and one Se(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one H(1), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Ca(1), one H(3), and one Se(2) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one H(2), and one Se(2) atom. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Ca(1), one H(2), and one Se(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one H(1), one H(3), and one H(4) atom.