Si5O8 crystallizes in the triclinic P1 space group. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one O(1), one O(10), one O(11), and one O(3) atom. In the second Si site, Si(2) is bonded to one O(12), one O(14), one O(2), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded in a trigonal non-coplanar geometry to one O(10), one O(13), and one O(15) atom. In the fourth Si site, Si(4) is bonded in a water-like geometry to one O(14) and one O(4) atom. In the fifth Si site, Si(5) is bonded in a distorted trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. In the sixth Si site, Si(6) is bonded to one O(12), one O(16), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. In the seventh Si site, Si(7) is bonded in a trigonal non-coplanar geometry to one O(11), one O(15), and one O(5) atom. In the eighth Si site, Si(8) is bonded in a tetrahedral geometry to one O(13), one O(5), one O(7), and one O(8) atom. In the ninth Si site, Si(9) is bonded in a water-like geometry to one O(16) and one O(2) atom. In the tenth Si site, Si(10) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(3), and one O(9) atom. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in an L-shaped geometry to one Si(1) and one Si(10) atom. In the second O site, O(2) is bonded in a linear geometry to one Si(2) and one Si(9) atom. In the third O site, O(3) is bonded in an L-shaped geometry to one Si(1) and one Si(10) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Si(4) and one Si(6) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(7) and one Si(8) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(5) and one Si(6) atom. In the seventh O site, O(7) is bonded in an L-shaped geometry to one Si(5) and one Si(8) atom. In the eighth O site, O(8) is bonded in an L-shaped geometry to one Si(5) and one Si(8) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(10) and one Si(2) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(7) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(6) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(8) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(7) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Si(6) and one Si(9) atom.
Si5O8 crystallizes in the triclinic P1 space group. There are ten inequivalent Si sites. In the first Si site, Si(1) is bonded in a tetrahedral geometry to one O(1), one O(10), one O(11), and one O(3) atom. The Si(1)-O(1) bond length is 1.69 Å. The Si(1)-O(10) bond length is 1.63 Å. The Si(1)-O(11) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.67 Å. In the second Si site, Si(2) is bonded to one O(12), one O(14), one O(2), and one O(9) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(12) bond length is 1.61 Å. The Si(2)-O(14) bond length is 1.63 Å. The Si(2)-O(2) bond length is 1.62 Å. The Si(2)-O(9) bond length is 1.65 Å. In the third Si site, Si(3) is bonded in a trigonal non-coplanar geometry to one O(10), one O(13), and one O(15) atom. The Si(3)-O(10) bond length is 1.66 Å. The Si(3)-O(13) bond length is 1.64 Å. The Si(3)-O(15) bond length is 1.66 Å. In the fourth Si site, Si(4) is bonded in a water-like geometry to one O(14) and one O(4) atom. The Si(4)-O(14) bond length is 1.66 Å. The Si(4)-O(4) bond length is 1.65 Å. In the fifth Si site, Si(5) is bonded in a distorted trigonal non-coplanar geometry to one O(6), one O(7), and one O(8) atom. The Si(5)-O(6) bond length is 1.63 Å. The Si(5)-O(7) bond length is 1.70 Å. The Si(5)-O(8) bond length is 1.70 Å. In the sixth Si site, Si(6) is bonded to one O(12), one O(16), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(6)-O(12) bond length is 1.62 Å. The Si(6)-O(16) bond length is 1.63 Å. The Si(6)-O(4) bond length is 1.62 Å. The Si(6)-O(6) bond length is 1.64 Å. In the seventh Si site, Si(7) is bonded in a trigonal non-coplanar geometry to one O(11), one O(15), and one O(5) atom. The Si(7)-O(11) bond length is 1.65 Å. The Si(7)-O(15) bond length is 1.66 Å. The Si(7)-O(5) bond length is 1.66 Å. In the eighth Si site, Si(8) is bonded in a tetrahedral geometry to one O(13), one O(5), one O(7), and one O(8) atom. The Si(8)-O(13) bond length is 1.63 Å. The Si(8)-O(5) bond length is 1.64 Å. The Si(8)-O(7) bond length is 1.67 Å. The Si(8)-O(8) bond length is 1.68 Å. In the ninth Si site, Si(9) is bonded in a water-like geometry to one O(16) and one O(2) atom. The Si(9)-O(16) bond length is 1.66 Å. The Si(9)-O(2) bond length is 1.65 Å. In the tenth Si site, Si(10) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(3), and one O(9) atom. The Si(10)-O(1) bond length is 1.70 Å. The Si(10)-O(3) bond length is 1.71 Å. The Si(10)-O(9) bond length is 1.63 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in an L-shaped geometry to one Si(1) and one Si(10) atom. In the second O site, O(2) is bonded in a linear geometry to one Si(2) and one Si(9) atom. In the third O site, O(3) is bonded in an L-shaped geometry to one Si(1) and one Si(10) atom. In the fourth O site, O(4) is bonded in a linear geometry to one Si(4) and one Si(6) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(7) and one Si(8) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Si(5) and one Si(6) atom. In the seventh O site, O(7) is bonded in an L-shaped geometry to one Si(5) and one Si(8) atom. In the eighth O site, O(8) is bonded in an L-shaped geometry to one Si(5) and one Si(8) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Si(10) and one Si(2) atom. In the tenth O site, O(10) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(7) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(6) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(8) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the fifteenth O site, O(15) is bonded in a bent 150 degrees geometry to one Si(3) and one Si(7) atom. In the sixteenth O site, O(16) is bonded in a bent 150 degrees geometry to one Si(6) and one Si(9) atom.