Na2Bi4O7 crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(1), and two equivalent O(3) atoms. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(4), and two equivalent O(2) atoms. In the second Bi site, Bi(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), one Bi(1), and one Bi(2) atom to form a mixture of edge and corner-sharing ONa2Bi2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Bi(2) and two equivalent Bi(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1) and two equivalent Bi(2) atoms. In the fourth O site, O(4) is bonded to two equivalent Na(1) and two equivalent Bi(1) atoms to form a mixture of distorted edge and corner-sharing ONa2Bi2 tetrahedra.
Na2Bi4O7 crystallizes in the monoclinic C2/c space group. Na(1) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(1), and two equivalent O(3) atoms. The Na(1)-O(4) bond length is 2.32 Å. There is one shorter (2.28 Å) and one longer (2.45 Å) Na(1)-O(1) bond length. There is one shorter (2.35 Å) and one longer (2.50 Å) Na(1)-O(3) bond length. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(4), and two equivalent O(2) atoms. The Bi(1)-O(1) bond length is 2.23 Å. The Bi(1)-O(4) bond length is 2.11 Å. There is one shorter (2.14 Å) and one longer (2.30 Å) Bi(1)-O(2) bond length. In the second Bi site, Bi(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), and two equivalent O(3) atoms. The Bi(2)-O(1) bond length is 2.07 Å. The Bi(2)-O(2) bond length is 2.37 Å. There is one shorter (2.08 Å) and one longer (2.28 Å) Bi(2)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Na(1), one Bi(1), and one Bi(2) atom to form a mixture of edge and corner-sharing ONa2Bi2 trigonal pyramids. In the second O site, O(2) is bonded in a distorted T-shaped geometry to one Bi(2) and two equivalent Bi(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Na(1) and two equivalent Bi(2) atoms. In the fourth O site, O(4) is bonded to two equivalent Na(1) and two equivalent Bi(1) atoms to form a mixture of distorted edge and corner-sharing ONa2Bi2 tetrahedra.