Cr(Si2O5)2 crystallizes in the triclinic P-1 space group. Cr(1) is bonded to one O(7), one O(8), one O(9), and two equivalent O(10) atoms to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and  an edgeedge with one Cr(1)O5 trigonal bipyramid. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Cr(1)O5 trigonal bipyramid. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Cr(1)O5 trigonal bipyramid. In the third Si site, Si(3) is bonded to one O(2), one O(3), one O(4), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Cr(1)O5 trigonal bipyramid. In the fourth Si site, Si(4) is bonded to one O(10), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Cr(1)O5 trigonal bipyramids. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(3) and one Si(4) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(4) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(2) and one Si(4) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cr(1) and one Si(1) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Cr(1) and one Si(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Cr(1) and one Si(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one Si(4) atom.
Cr(Si2O5)2 crystallizes in the triclinic P-1 space group. Cr(1) is bonded to one O(7), one O(8), one O(9), and two equivalent O(10) atoms to form distorted CrO5 trigonal bipyramids that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, corners with two equivalent Si(4)O4 tetrahedra, and  an edgeedge with one Cr(1)O5 trigonal bipyramid. The Cr(1)-O(7) bond length is 1.85 Å. The Cr(1)-O(8) bond length is 1.80 Å. The Cr(1)-O(9) bond length is 1.79 Å. There is one shorter (1.88 Å) and one longer (2.25 Å) Cr(1)-O(10) bond length. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Cr(1)O5 trigonal bipyramid. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.65 Å. The Si(1)-O(7) bond length is 1.62 Å. In the second Si site, Si(2) is bonded to one O(1), one O(2), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Cr(1)O5 trigonal bipyramid. The Si(2)-O(1) bond length is 1.64 Å. The Si(2)-O(2) bond length is 1.63 Å. The Si(2)-O(6) bond length is 1.64 Å. The Si(2)-O(8) bond length is 1.63 Å. In the third Si site, Si(3) is bonded to one O(2), one O(3), one O(4), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  a cornercorner with one Cr(1)O5 trigonal bipyramid. The Si(3)-O(2) bond length is 1.62 Å. The Si(3)-O(3) bond length is 1.63 Å. The Si(3)-O(4) bond length is 1.63 Å. The Si(3)-O(9) bond length is 1.64 Å. In the fourth Si site, Si(4) is bonded to one O(10), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and corners with two equivalent Cr(1)O5 trigonal bipyramids. The Si(4)-O(10) bond length is 1.68 Å. The Si(4)-O(4) bond length is 1.62 Å. The Si(4)-O(5) bond length is 1.62 Å. The Si(4)-O(6) bond length is 1.63 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(3) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(3) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(3) and one Si(4) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(4) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(2) and one Si(4) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one Cr(1) and one Si(1) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Cr(1) and one Si(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Cr(1) and one Si(3) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to two equivalent Cr(1) and one Si(4) atom.