Na2Cu5(Si2O7)2 crystallizes in the triclinic P-1 space group. Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(7), and two equivalent O(5) atoms. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), one O(6), and one O(7) atom. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(6) and two equivalent O(7) atoms. In the third Cu site, Cu(3) is bonded in a rectangular see-saw-like geometry to one O(3), one O(5), and two equivalent O(4) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(5), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded to one Na(1), one Cu(1), one Cu(3), and one Si(2) atom to form distorted ONaCu2Si tetrahedra that share  a cornercorner with one O(5)Na2CuSi trigonal pyramid, corners with two equivalent O(7)NaCu2Si trigonal pyramids, and  an edgeedge with one O(5)Na2CuSi trigonal pyramid. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Cu(3) and one Si(2) atom. In the fifth O site, O(5) is bonded to two equivalent Na(1), one Cu(3), and one Si(1) atom to form distorted ONa2CuSi trigonal pyramids that share  a cornercorner with one O(3)NaCu2Si tetrahedra,  a cornercorner with one O(7)NaCu2Si trigonal pyramid,  an edgeedge with one O(3)NaCu2Si tetrahedra,  an edgeedge with one O(5)Na2CuSi trigonal pyramid, and  an edgeedge with one O(7)NaCu2Si trigonal pyramid. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Cu(1), one Cu(2), and one Si(2) atom. In the seventh O site, O(7) is bonded to one Na(1), one Cu(1), one Cu(2), and one Si(1) atom to form distorted ONaCu2Si trigonal pyramids that share corners with two equivalent O(3)NaCu2Si tetrahedra,  a cornercorner with one O(5)Na2CuSi trigonal pyramid,  a cornercorner with one O(7)NaCu2Si trigonal pyramid, and  an edgeedge with one O(5)Na2CuSi trigonal pyramid.
Na2Cu5(Si2O7)2 crystallizes in the triclinic P-1 space group. Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(3), one O(7), and two equivalent O(5) atoms. The Na(1)-O(1) bond length is 2.54 Å. The Na(1)-O(2) bond length is 2.35 Å. The Na(1)-O(3) bond length is 2.41 Å. The Na(1)-O(7) bond length is 2.53 Å. There is one shorter (2.35 Å) and one longer (2.36 Å) Na(1)-O(5) bond length. There are three inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), one O(6), and one O(7) atom. The Cu(1)-O(1) bond length is 1.92 Å. The Cu(1)-O(3) bond length is 1.98 Å. The Cu(1)-O(6) bond length is 1.96 Å. The Cu(1)-O(7) bond length is 1.98 Å. In the second Cu site, Cu(2) is bonded in a square co-planar geometry to two equivalent O(6) and two equivalent O(7) atoms. Both Cu(2)-O(6) bond lengths are 1.94 Å. Both Cu(2)-O(7) bond lengths are 1.97 Å. In the third Cu site, Cu(3) is bonded in a rectangular see-saw-like geometry to one O(3), one O(5), and two equivalent O(4) atoms. The Cu(3)-O(3) bond length is 2.02 Å. The Cu(3)-O(5) bond length is 1.89 Å. There is one shorter (1.94 Å) and one longer (2.00 Å) Cu(3)-O(4) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(5), and one O(7) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.62 Å. The Si(1)-O(2) bond length is 1.68 Å. The Si(1)-O(5) bond length is 1.63 Å. The Si(1)-O(7) bond length is 1.67 Å. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.66 Å. The Si(2)-O(4) bond length is 1.64 Å. The Si(2)-O(6) bond length is 1.65 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Cu(1), and one Si(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded to one Na(1), one Cu(1), one Cu(3), and one Si(2) atom to form distorted ONaCu2Si tetrahedra that share  a cornercorner with one O(5)Na2CuSi trigonal pyramid, corners with two equivalent O(7)NaCu2Si trigonal pyramids, and  an edgeedge with one O(5)Na2CuSi trigonal pyramid. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Cu(3) and one Si(2) atom. In the fifth O site, O(5) is bonded to two equivalent Na(1), one Cu(3), and one Si(1) atom to form distorted ONa2CuSi trigonal pyramids that share  a cornercorner with one O(3)NaCu2Si tetrahedra,  a cornercorner with one O(7)NaCu2Si trigonal pyramid,  an edgeedge with one O(3)NaCu2Si tetrahedra,  an edgeedge with one O(5)Na2CuSi trigonal pyramid, and  an edgeedge with one O(7)NaCu2Si trigonal pyramid. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Cu(1), one Cu(2), and one Si(2) atom. In the seventh O site, O(7) is bonded to one Na(1), one Cu(1), one Cu(2), and one Si(1) atom to form distorted ONaCu2Si trigonal pyramids that share corners with two equivalent O(3)NaCu2Si tetrahedra,  a cornercorner with one O(5)Na2CuSi trigonal pyramid,  a cornercorner with one O(7)NaCu2Si trigonal pyramid, and  an edgeedge with one O(5)Na2CuSi trigonal pyramid.