Nb2Se4O13 crystallizes in the monoclinic Pc space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(12), one O(13), one O(5), one O(6), and two equivalent O(4) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 32°. In the second Nb site, Nb(2) is bonded to one O(10), one O(7), one O(8), one O(9), and two equivalent O(11) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 32°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted T-shaped geometry to one O(2), one O(3), and one O(5) atom. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(10), and one O(3) atom. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one O(13), one O(6), and one O(7) atom. In the fourth Se site, Se(4) is bonded in a distorted trigonal non-coplanar geometry to one O(12), one O(8), and one O(9) atom. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Se(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Se(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Se(1) and one Se(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Nb(1) and one Se(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(1) and one Se(3) atom. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(2) and one Se(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(2) and one Se(4) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(2) and one Se(4) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Nb(2) and one Se(2) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to two equivalent Nb(2) atoms. In the twelfth O site, O(12) is bonded in a linear geometry to one Nb(1) and one Se(4) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Nb(1) and one Se(3) atom.
Nb2Se4O13 crystallizes in the monoclinic Pc space group. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to one O(12), one O(13), one O(5), one O(6), and two equivalent O(4) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 32°. The Nb(1)-O(12) bond length is 2.00 Å. The Nb(1)-O(13) bond length is 2.02 Å. The Nb(1)-O(5) bond length is 2.01 Å. The Nb(1)-O(6) bond length is 2.04 Å. There is one shorter (1.82 Å) and one longer (2.14 Å) Nb(1)-O(4) bond length. In the second Nb site, Nb(2) is bonded to one O(10), one O(7), one O(8), one O(9), and two equivalent O(11) atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 32°. The Nb(2)-O(10) bond length is 1.98 Å. The Nb(2)-O(7) bond length is 2.02 Å. The Nb(2)-O(8) bond length is 2.02 Å. The Nb(2)-O(9) bond length is 2.04 Å. There is one shorter (1.82 Å) and one longer (2.15 Å) Nb(2)-O(11) bond length. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted T-shaped geometry to one O(2), one O(3), and one O(5) atom. The Se(1)-O(2) bond length is 1.64 Å. The Se(1)-O(3) bond length is 1.84 Å. The Se(1)-O(5) bond length is 1.75 Å. In the second Se site, Se(2) is bonded in a distorted trigonal non-coplanar geometry to one O(1), one O(10), and one O(3) atom. The Se(2)-O(1) bond length is 1.64 Å. The Se(2)-O(10) bond length is 1.73 Å. The Se(2)-O(3) bond length is 1.82 Å. In the third Se site, Se(3) is bonded in a trigonal non-coplanar geometry to one O(13), one O(6), and one O(7) atom. The Se(3)-O(13) bond length is 1.72 Å. The Se(3)-O(6) bond length is 1.71 Å. The Se(3)-O(7) bond length is 1.70 Å. In the fourth Se site, Se(4) is bonded in a distorted trigonal non-coplanar geometry to one O(12), one O(8), and one O(9) atom. The Se(4)-O(12) bond length is 1.71 Å. The Se(4)-O(8) bond length is 1.73 Å. The Se(4)-O(9) bond length is 1.71 Å. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Se(2) atom. In the second O site, O(2) is bonded in a single-bond geometry to one Se(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Se(1) and one Se(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Nb(1) and one Se(1) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Nb(1) and one Se(3) atom. In the seventh O site, O(7) is bonded in a linear geometry to one Nb(2) and one Se(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Nb(2) and one Se(4) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Nb(2) and one Se(4) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Nb(2) and one Se(2) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to two equivalent Nb(2) atoms. In the twelfth O site, O(12) is bonded in a linear geometry to one Nb(1) and one Se(4) atom. In the thirteenth O site, O(13) is bonded in a bent 150 degrees geometry to one Nb(1) and one Se(3) atom.