Na2W2O5 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(9), and two equivalent O(7) atoms. In the second Na site, Na(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(6), and two equivalent O(8) atoms. In the third Na site, Na(3) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(3), one O(4), one O(7), and two equivalent O(5) atoms. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(6), one O(9), and two equivalent O(8) atoms. There are four inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form WO6 octahedra that share corners with four equivalent W(2)O6 octahedra and  a cornercorner with one W(3)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 7-20°. In the second W site, W(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form WO6 octahedra that share corners with four equivalent W(1)O6 octahedra and  a cornercorner with one W(3)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 7-20°. In the third W site, W(3) is bonded to one O(10), one O(5), one O(8), and one O(9) atom to form corner-sharing WO4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 12-14°. In the fourth W site, W(4) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(6), one O(7), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one W(1), and one W(2) atom to form distorted ONa4W2 octahedra that share corners with two equivalent O(4)Na4W2 octahedra, corners with two equivalent O(10)Na2W2 trigonal pyramids, corners with two equivalent O(9)Na2W2 trigonal pyramids, and edges with two equivalent O(4)Na4W2 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Na(4), one W(1), and one W(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(3), one W(1), and one W(2) atom. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one W(1), and one W(2) atom to form distorted ONa4W2 octahedra that share corners with two equivalent O(1)Na4W2 octahedra, corners with two equivalent O(10)Na2W2 trigonal pyramids, corners with two equivalent O(9)Na2W2 trigonal pyramids, and edges with two equivalent O(1)Na4W2 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(3), one W(1), and one W(3) atom. In the sixth O site, O(6) is bonded in a distorted see-saw-like geometry to one Na(2), one Na(4), one W(1), and one W(4) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one Na(3), two equivalent Na(1), one W(2), and one W(4) atom. In the eighth O site, O(8) is bonded in a 6-coordinate geometry to two equivalent Na(2), two equivalent Na(4), one W(2), and one W(3) atom. In the ninth O site, O(9) is bonded to one Na(1), one Na(4), one W(3), and one W(4) atom to form distorted ONa2W2 trigonal pyramids that share corners with two equivalent O(1)Na4W2 octahedra, corners with two equivalent O(4)Na4W2 octahedra, and corners with two equivalent O(10)Na2W2 trigonal pyramids. The corner-sharing octahedral tilt angles range from 18-81°. In the tenth O site, O(10) is bonded to one Na(2), one Na(3), one W(3), and one W(4) atom to form ONa2W2 trigonal pyramids that share corners with two equivalent O(1)Na4W2 octahedra, corners with two equivalent O(4)Na4W2 octahedra, and corners with two equivalent O(9)Na2W2 trigonal pyramids. The corner-sharing octahedral tilt angles range from 45-59°.
Na2W2O5 crystallizes in the triclinic P1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(9), and two equivalent O(7) atoms. The Na(1)-O(1) bond length is 2.64 Å. The Na(1)-O(2) bond length is 2.96 Å. The Na(1)-O(3) bond length is 2.40 Å. The Na(1)-O(4) bond length is 2.87 Å. The Na(1)-O(5) bond length is 2.72 Å. The Na(1)-O(9) bond length is 2.48 Å. There is one shorter (2.64 Å) and one longer (3.00 Å) Na(1)-O(7) bond length. In the second Na site, Na(2) is bonded in a 8-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), one O(6), and two equivalent O(8) atoms. The Na(2)-O(1) bond length is 2.83 Å. The Na(2)-O(10) bond length is 2.36 Å. The Na(2)-O(2) bond length is 2.34 Å. The Na(2)-O(3) bond length is 2.76 Å. The Na(2)-O(4) bond length is 2.49 Å. The Na(2)-O(6) bond length is 2.65 Å. There is one shorter (2.78 Å) and one longer (2.90 Å) Na(2)-O(8) bond length. In the third Na site, Na(3) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(3), one O(4), one O(7), and two equivalent O(5) atoms. The Na(3)-O(1) bond length is 2.40 Å. The Na(3)-O(10) bond length is 2.35 Å. The Na(3)-O(3) bond length is 2.41 Å. The Na(3)-O(4) bond length is 2.60 Å. The Na(3)-O(7) bond length is 2.83 Å. There is one shorter (2.78 Å) and one longer (2.91 Å) Na(3)-O(5) bond length. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(6), one O(9), and two equivalent O(8) atoms. The Na(4)-O(1) bond length is 2.67 Å. The Na(4)-O(2) bond length is 2.43 Å. The Na(4)-O(4) bond length is 2.55 Å. The Na(4)-O(6) bond length is 2.63 Å. The Na(4)-O(9) bond length is 2.46 Å. There is one shorter (2.91 Å) and one longer (2.96 Å) Na(4)-O(8) bond length. There are four inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form WO6 octahedra that share corners with four equivalent W(2)O6 octahedra and  a cornercorner with one W(3)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 7-20°. The W(1)-O(1) bond length is 2.03 Å. The W(1)-O(2) bond length is 1.94 Å. The W(1)-O(3) bond length is 1.95 Å. The W(1)-O(4) bond length is 2.04 Å. The W(1)-O(5) bond length is 2.02 Å. The W(1)-O(6) bond length is 2.10 Å. In the second W site, W(2) is bonded to one O(1), one O(2), one O(3), one O(4), one O(7), and one O(8) atom to form WO6 octahedra that share corners with four equivalent W(1)O6 octahedra and  a cornercorner with one W(3)O4 trigonal pyramid. The corner-sharing octahedral tilt angles range from 7-20°. The W(2)-O(1) bond length is 2.04 Å. The W(2)-O(2) bond length is 2.12 Å. The W(2)-O(3) bond length is 2.11 Å. The W(2)-O(4) bond length is 2.05 Å. The W(2)-O(7) bond length is 2.09 Å. The W(2)-O(8) bond length is 2.03 Å. In the third W site, W(3) is bonded to one O(10), one O(5), one O(8), and one O(9) atom to form corner-sharing WO4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 12-14°. The W(3)-O(10) bond length is 1.98 Å. The W(3)-O(5) bond length is 1.98 Å. The W(3)-O(8) bond length is 1.97 Å. The W(3)-O(9) bond length is 2.08 Å. In the fourth W site, W(4) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(6), one O(7), and one O(9) atom. The W(4)-O(10) bond length is 2.17 Å. The W(4)-O(6) bond length is 1.92 Å. The W(4)-O(7) bond length is 1.92 Å. The W(4)-O(9) bond length is 1.98 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one W(1), and one W(2) atom to form distorted ONa4W2 octahedra that share corners with two equivalent O(4)Na4W2 octahedra, corners with two equivalent O(10)Na2W2 trigonal pyramids, corners with two equivalent O(9)Na2W2 trigonal pyramids, and edges with two equivalent O(4)Na4W2 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Na(4), one W(1), and one W(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), one Na(2), one Na(3), one W(1), and one W(2) atom. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one W(1), and one W(2) atom to form distorted ONa4W2 octahedra that share corners with two equivalent O(1)Na4W2 octahedra, corners with two equivalent O(10)Na2W2 trigonal pyramids, corners with two equivalent O(9)Na2W2 trigonal pyramids, and edges with two equivalent O(1)Na4W2 octahedra. The corner-sharing octahedral tilt angles range from 1-2°. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(3), one W(1), and one W(3) atom. In the sixth O site, O(6) is bonded in a distorted see-saw-like geometry to one Na(2), one Na(4), one W(1), and one W(4) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one Na(3), two equivalent Na(1), one W(2), and one W(4) atom. In the eighth O site, O(8) is bonded in a 6-coordinate geometry to two equivalent Na(2), two equivalent Na(4), one W(2), and one W(3) atom. In the ninth O site, O(9) is bonded to one Na(1), one Na(4), one W(3), and one W(4) atom to form distorted ONa2W2 trigonal pyramids that share corners with two equivalent O(1)Na4W2 octahedra, corners with two equivalent O(4)Na4W2 octahedra, and corners with two equivalent O(10)Na2W2 trigonal pyramids. The corner-sharing octahedral tilt angles range from 18-81°. In the tenth O site, O(10) is bonded to one Na(2), one Na(3), one W(3), and one W(4) atom to form ONa2W2 trigonal pyramids that share corners with two equivalent O(1)Na4W2 octahedra, corners with two equivalent O(4)Na4W2 octahedra, and corners with two equivalent O(9)Na2W2 trigonal pyramids. The corner-sharing octahedral tilt angles range from 45-59°.