NaSmSe2O7 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 7-coordinate geometry to one O(3), one O(5), two equivalent O(6), and three equivalent O(7) atoms. Sm(1) is bonded in a 10-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(3), two equivalent O(4), and three equivalent O(2) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(2), one O(3), and one O(4) atom. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(1), one O(5), one O(6), and one O(7) atom. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Sm(1) and one Se(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Sm(1) and one Se(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(1), two equivalent Sm(1), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Sm(1) and one Se(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Sm(1), and one Se(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Na(1) and one Se(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to three equivalent Na(1) and one Se(2) atom.
NaSmSe2O7 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded in a 7-coordinate geometry to one O(3), one O(5), two equivalent O(6), and three equivalent O(7) atoms. The Na(1)-O(3) bond length is 2.94 Å. The Na(1)-O(5) bond length is 2.32 Å. There is one shorter (2.45 Å) and one longer (2.47 Å) Na(1)-O(6) bond length. There are a spread of Na(1)-O(7) bond distances ranging from 2.38-2.82 Å. Sm(1) is bonded in a 10-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(3), two equivalent O(4), and three equivalent O(2) atoms. The Sm(1)-O(5) bond length is 2.53 Å. There is one shorter (2.40 Å) and one longer (2.57 Å) Sm(1)-O(1) bond length. There is one shorter (2.45 Å) and one longer (3.08 Å) Sm(1)-O(3) bond length. There is one shorter (2.41 Å) and one longer (2.44 Å) Sm(1)-O(4) bond length. There are a spread of Sm(1)-O(2) bond distances ranging from 2.42-2.76 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted trigonal non-coplanar geometry to one O(2), one O(3), and one O(4) atom. The Se(1)-O(2) bond length is 1.74 Å. The Se(1)-O(3) bond length is 1.68 Å. The Se(1)-O(4) bond length is 1.72 Å. In the second Se site, Se(2) is bonded in a tetrahedral geometry to one O(1), one O(5), one O(6), and one O(7) atom. The Se(2)-O(1) bond length is 1.67 Å. The Se(2)-O(5) bond length is 1.66 Å. The Se(2)-O(6) bond length is 1.64 Å. The Se(2)-O(7) bond length is 1.64 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Sm(1) and one Se(2) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to three equivalent Sm(1) and one Se(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(1), two equivalent Sm(1), and one Se(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to two equivalent Sm(1) and one Se(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Sm(1), and one Se(2) atom. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Na(1) and one Se(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to three equivalent Na(1) and one Se(2) atom.