Cs4CuSi2O7 crystallizes in the triclinic P-1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing SiO4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Cs(1), two equivalent Cs(2), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1), three equivalent Cs(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), one Cu(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Cs(2) and two equivalent Si(1) atoms.
Cs4CuSi2O7 crystallizes in the triclinic P-1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(2), and two equivalent O(3) atoms. The Cs(1)-O(1) bond length is 3.01 Å. There is one shorter (2.96 Å) and one longer (3.02 Å) Cs(1)-O(2) bond length. There is one shorter (3.02 Å) and one longer (3.05 Å) Cs(1)-O(3) bond length. In the second Cs site, Cs(2) is bonded in a 8-coordinate geometry to one O(4), two equivalent O(1), two equivalent O(3), and three equivalent O(2) atoms. The Cs(2)-O(4) bond length is 3.37 Å. There is one shorter (3.33 Å) and one longer (3.37 Å) Cs(2)-O(1) bond length. There is one shorter (3.16 Å) and one longer (3.19 Å) Cs(2)-O(3) bond length. There are a spread of Cs(2)-O(2) bond distances ranging from 2.98-3.58 Å. Cu(1) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(3) atoms. Both Cu(1)-O(1) bond lengths are 1.98 Å. Both Cu(1)-O(3) bond lengths are 1.96 Å. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.65 Å. The Si(1)-O(2) bond length is 1.60 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.66 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to one Cs(1), two equivalent Cs(2), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to two equivalent Cs(1), three equivalent Cs(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to two equivalent Cs(1), two equivalent Cs(2), one Cu(1), and one Si(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Cs(2) and two equivalent Si(1) atoms.