Na2Ca2(SO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Ca(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 CaO6 octahedra that share corners with two equivalent S(2)O4 tetrahedra and corners with four equivalent S(1)O4 tetrahedra. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SO4 tetrahedra that share corners with four equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-38°. In the second S site, S(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form SO4 tetrahedra that share corners with four equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-39°. There are six inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Ca(1), and one S(1) atom. In the second O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ca(1), and one S(2) atom. In the third O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ca(1), and one S(1) atom. In the fourth O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Ca(1), and one S(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Ca(1) and one S(2) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Ca(1), and one S(1) atom.
Na2Ca2(SO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. Both Na(1)-O(1) bond lengths are 2.97 Å. Both Na(1)-O(3) bond lengths are 2.89 Å. Both Na(1)-O(5) bond lengths are 2.48 Å. Both Na(1)-O(6) bond lengths are 2.51 Å. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Both Na(2)-O(4) bond lengths are 2.79 Å. Both Na(2)-O(5) bond lengths are 2.72 Å. Both Na(2)-O(6) bond lengths are 2.75 Å. Ca(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 CaO6 octahedra that share corners with two equivalent S(2)O4 tetrahedra and corners with four equivalent S(1)O4 tetrahedra. The Ca(1)-O(1) bond length is 2.27 Å. The Ca(1)-O(2) bond length is 2.25 Å. The Ca(1)-O(3) bond length is 2.35 Å. The Ca(1)-O(4) bond length is 2.33 Å. The Ca(1)-O(5) bond length is 2.36 Å. The Ca(1)-O(6) bond length is 2.38 Å. There are two inequivalent S sites. In the first S site, S(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SO4 tetrahedra that share corners with four equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-38°. The S(1)-O(1) bond length is 1.48 Å. The S(1)-O(3) bond length is 1.49 Å. The S(1)-O(4) bond length is 1.48 Å. The S(1)-O(6) bond length is 1.50 Å. In the second S site, S(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form SO4 tetrahedra that share corners with four equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-39°. Both S(2)-O(2) bond lengths are 1.47 Å. Both S(2)-O(5) bond lengths are 1.50 Å. There are six inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Ca(1), and one S(1) atom. In the second O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ca(1), and one S(2) atom. In the third O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Ca(1), and one S(1) atom. In the fourth O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Ca(1), and one S(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Ca(1) and one S(2) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Ca(1), and one S(1) atom.