Na2CaNb4Bi2O15 crystallizes in the orthorhombic Cmc2_1 space group. Na(1) is bonded in a 9-coordinate geometry to one O(8), two equivalent O(5), two equivalent O(7), and four equivalent O(2) atoms. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(4), two equivalent O(8), and four equivalent O(1) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(8) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 5-34°. In the second Nb site, Nb(2) is bonded to one O(2), one O(6), two equivalent O(5), and two equivalent O(7) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 5-27°. Bi(1) is bonded in a 6-coordinate geometry to two equivalent O(6) and four equivalent O(3) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ca(1) and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to four equivalent Na(1), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded to four equivalent Bi(1) atoms to form a mixture of corner and edge-sharing OBi4 tetrahedra. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to two equivalent Ca(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1) and two equivalent Nb(2) atoms. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Nb(2) and two equivalent Bi(1) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Na(1) and two equivalent Nb(2) atoms. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to one Na(1), one Ca(1), and two equivalent Nb(1) atoms.
Na2CaNb4Bi2O15 crystallizes in the orthorhombic Cmc2_1 space group. Na(1) is bonded in a 9-coordinate geometry to one O(8), two equivalent O(5), two equivalent O(7), and four equivalent O(2) atoms. The Na(1)-O(8) bond length is 2.55 Å. There is one shorter (2.51 Å) and one longer (2.71 Å) Na(1)-O(5) bond length. There is one shorter (2.34 Å) and one longer (2.90 Å) Na(1)-O(7) bond length. There are a spread of Na(1)-O(2) bond distances ranging from 2.69-2.93 Å. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(4), two equivalent O(8), and four equivalent O(1) atoms. There is one shorter (2.42 Å) and one longer (2.46 Å) Ca(1)-O(4) bond length. Both Ca(1)-O(8) bond lengths are 2.43 Å. There are two shorter (2.50 Å) and two longer (2.80 Å) Ca(1)-O(1) bond lengths. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(8) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 5-34°. The Nb(1)-O(2) bond length is 1.88 Å. The Nb(1)-O(4) bond length is 2.13 Å. There is one shorter (1.96 Å) and one longer (2.14 Å) Nb(1)-O(1) bond length. There is one shorter (1.95 Å) and one longer (2.11 Å) Nb(1)-O(8) bond length. In the second Nb site, Nb(2) is bonded to one O(2), one O(6), two equivalent O(5), and two equivalent O(7) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 5-27°. The Nb(2)-O(2) bond length is 2.27 Å. The Nb(2)-O(6) bond length is 1.90 Å. There is one shorter (1.94 Å) and one longer (2.08 Å) Nb(2)-O(5) bond length. There is one shorter (1.92 Å) and one longer (2.06 Å) Nb(2)-O(7) bond length. Bi(1) is bonded in a 6-coordinate geometry to two equivalent O(6) and four equivalent O(3) atoms. There is one shorter (2.54 Å) and one longer (2.62 Å) Bi(1)-O(6) bond length. There are a spread of Bi(1)-O(3) bond distances ranging from 2.21-2.53 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to two equivalent Ca(1) and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a 6-coordinate geometry to four equivalent Na(1), one Nb(1), and one Nb(2) atom. In the third O site, O(3) is bonded to four equivalent Bi(1) atoms to form a mixture of corner and edge-sharing OBi4 tetrahedra. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to two equivalent Ca(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Na(1) and two equivalent Nb(2) atoms. In the sixth O site, O(6) is bonded in a distorted single-bond geometry to one Nb(2) and two equivalent Bi(1) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Na(1) and two equivalent Nb(2) atoms. In the eighth O site, O(8) is bonded in a distorted see-saw-like geometry to one Na(1), one Ca(1), and two equivalent Nb(1) atoms.