Si2H2O5 crystallizes in the triclinic P1 space group. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(5), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(2), one O(4), one O(5), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(10), one O(2), one O(3), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. In the second H site, H(2) is bonded in a distorted single-bond geometry to one O(7) and one O(9) atom. In the third H site, H(3) is bonded in a linear geometry to one O(8) and one O(9) atom. In the fourth H site, H(4) is bonded in a linear geometry to one O(10) and one O(8) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Si(1), one Si(2), and one H(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Si(1) and one H(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Si(2), one H(3), and one H(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Si(3), one H(2), and one H(3) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Si(4) and one H(4) atom.
Si2H2O5 crystallizes in the triclinic P1 space group. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(6), and one O(7) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.78 Å. The Si(1)-O(3) bond length is 1.61 Å. The Si(1)-O(6) bond length is 1.60 Å. The Si(1)-O(7) bond length is 1.59 Å. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(5), and one O(8) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(1) bond length is 1.80 Å. The Si(2)-O(4) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.63 Å. The Si(2)-O(8) bond length is 1.57 Å. In the third Si site, Si(3) is bonded to one O(2), one O(4), one O(5), and one O(9) atom to form corner-sharing SiO4 tetrahedra. The Si(3)-O(2) bond length is 1.63 Å. The Si(3)-O(4) bond length is 1.64 Å. The Si(3)-O(5) bond length is 1.65 Å. The Si(3)-O(9) bond length is 1.62 Å. In the fourth Si site, Si(4) is bonded to one O(10), one O(2), one O(3), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(4)-O(10) bond length is 1.59 Å. The Si(4)-O(2) bond length is 1.64 Å. The Si(4)-O(3) bond length is 1.65 Å. The Si(4)-O(6) bond length is 1.64 Å. There are four inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.98 Å. In the second H site, H(2) is bonded in a distorted single-bond geometry to one O(7) and one O(9) atom. The H(2)-O(7) bond length is 1.00 Å. The H(2)-O(9) bond length is 1.67 Å. In the third H site, H(3) is bonded in a linear geometry to one O(8) and one O(9) atom. The H(3)-O(8) bond length is 1.45 Å. The H(3)-O(9) bond length is 1.05 Å. In the fourth H site, H(4) is bonded in a linear geometry to one O(10) and one O(8) atom. The H(4)-O(10) bond length is 1.02 Å. The H(4)-O(8) bond length is 1.57 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Si(1), one Si(2), and one H(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(4) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Si(1) and one H(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Si(2), one H(3), and one H(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Si(3), one H(2), and one H(3) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Si(4) and one H(4) atom.