Cs3Nb2AsSe11 crystallizes in the monoclinic Cc space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 11-coordinate geometry to one As(1), one Se(10), one Se(2), one Se(3), one Se(4), one Se(8), one Se(9), two equivalent Se(1), and two equivalent Se(6) atoms. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one Se(10), one Se(11), one Se(2), one Se(4), one Se(6), two equivalent Se(7), and two equivalent Se(8) atoms. In the third Cs site, Cs(3) is bonded in a 9-coordinate geometry to one As(1), one Se(11), one Se(4), one Se(8), one Se(9), two equivalent Se(3), and two equivalent Se(7) atoms. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to one Se(1), one Se(10), one Se(11), one Se(4), one Se(6), one Se(7), and one Se(9) atom. In the second Nb site, Nb(2) is bonded in a distorted pentagonal bipyramidal geometry to one Se(10), one Se(2), one Se(3), one Se(4), one Se(5), one Se(8), and one Se(9) atom. As(1) is bonded in a 3-coordinate geometry to one Cs(1), one Cs(3), one Se(1), one Se(3), and one Se(5) atom. There are eleven inequivalent Se sites. In the first Se site, Se(7) is bonded in a 5-coordinate geometry to two equivalent Cs(2), two equivalent Cs(3), and one Nb(1) atom. In the second Se site, Se(8) is bonded in a distorted single-bond geometry to one Cs(1), one Cs(3), two equivalent Cs(2), and one Nb(2) atom. In the third Se site, Se(9) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(3), one Nb(1), one Nb(2), and one Se(11) atom. In the fourth Se site, Se(10) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(2), one Nb(1), one Nb(2), and one Se(2) atom. In the fifth Se site, Se(11) is bonded in a 4-coordinate geometry to one Cs(2), one Cs(3), one Nb(1), and one Se(9) atom. In the sixth Se site, Se(1) is bonded in a 4-coordinate geometry to two equivalent Cs(1), one Nb(1), and one As(1) atom. In the seventh Se site, Se(2) is bonded in a 4-coordinate geometry to one Cs(1), one Cs(2), one Nb(2), and one Se(10) atom. In the eighth Se site, Se(3) is bonded in a distorted L-shaped geometry to one Cs(1), two equivalent Cs(3), one Nb(2), and one As(1) atom. In the ninth Se site, Se(4) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Nb(1), and one Nb(2) atom. In the tenth Se site, Se(5) is bonded in an L-shaped geometry to one Nb(2) and one As(1) atom. In the eleventh Se site, Se(6) is bonded in a distorted single-bond geometry to one Cs(2), two equivalent Cs(1), and one Nb(1) atom.
Cs3Nb2AsSe11 crystallizes in the monoclinic Cc space group. There are three inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 11-coordinate geometry to one As(1), one Se(10), one Se(2), one Se(3), one Se(4), one Se(8), one Se(9), two equivalent Se(1), and two equivalent Se(6) atoms. The Cs(1)-As(1) bond length is 4.28 Å. The Cs(1)-Se(10) bond length is 3.97 Å. The Cs(1)-Se(2) bond length is 3.84 Å. The Cs(1)-Se(3) bond length is 4.01 Å. The Cs(1)-Se(4) bond length is 4.26 Å. The Cs(1)-Se(8) bond length is 3.97 Å. The Cs(1)-Se(9) bond length is 4.14 Å. There is one shorter (3.68 Å) and one longer (3.89 Å) Cs(1)-Se(1) bond length. There is one shorter (3.87 Å) and one longer (4.27 Å) Cs(1)-Se(6) bond length. In the second Cs site, Cs(2) is bonded in a 9-coordinate geometry to one Se(10), one Se(11), one Se(2), one Se(4), one Se(6), two equivalent Se(7), and two equivalent Se(8) atoms. The Cs(2)-Se(10) bond length is 3.85 Å. The Cs(2)-Se(11) bond length is 3.74 Å. The Cs(2)-Se(2) bond length is 3.63 Å. The Cs(2)-Se(4) bond length is 3.82 Å. The Cs(2)-Se(6) bond length is 3.78 Å. There is one shorter (3.70 Å) and one longer (3.80 Å) Cs(2)-Se(7) bond length. Both Cs(2)-Se(8) bond lengths are 3.82 Å. In the third Cs site, Cs(3) is bonded in a 9-coordinate geometry to one As(1), one Se(11), one Se(4), one Se(8), one Se(9), two equivalent Se(3), and two equivalent Se(7) atoms. The Cs(3)-As(1) bond length is 3.80 Å. The Cs(3)-Se(11) bond length is 3.61 Å. The Cs(3)-Se(4) bond length is 4.28 Å. The Cs(3)-Se(8) bond length is 3.77 Å. The Cs(3)-Se(9) bond length is 4.12 Å. There is one shorter (4.01 Å) and one longer (4.02 Å) Cs(3)-Se(3) bond length. There is one shorter (3.55 Å) and one longer (3.81 Å) Cs(3)-Se(7) bond length. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 7-coordinate geometry to one Se(1), one Se(10), one Se(11), one Se(4), one Se(6), one Se(7), and one Se(9) atom. The Nb(1)-Se(1) bond length is 2.67 Å. The Nb(1)-Se(10) bond length is 2.94 Å. The Nb(1)-Se(11) bond length is 2.64 Å. The Nb(1)-Se(4) bond length is 2.65 Å. The Nb(1)-Se(6) bond length is 2.60 Å. The Nb(1)-Se(7) bond length is 2.37 Å. The Nb(1)-Se(9) bond length is 2.69 Å. In the second Nb site, Nb(2) is bonded in a distorted pentagonal bipyramidal geometry to one Se(10), one Se(2), one Se(3), one Se(4), one Se(5), one Se(8), and one Se(9) atom. The Nb(2)-Se(10) bond length is 2.62 Å. The Nb(2)-Se(2) bond length is 2.61 Å. The Nb(2)-Se(3) bond length is 2.74 Å. The Nb(2)-Se(4) bond length is 2.98 Å. The Nb(2)-Se(5) bond length is 2.65 Å. The Nb(2)-Se(8) bond length is 2.36 Å. The Nb(2)-Se(9) bond length is 2.77 Å. As(1) is bonded in a 3-coordinate geometry to one Cs(1), one Cs(3), one Se(1), one Se(3), and one Se(5) atom. The As(1)-Se(1) bond length is 2.42 Å. The As(1)-Se(3) bond length is 2.48 Å. The As(1)-Se(5) bond length is 2.41 Å. There are eleven inequivalent Se sites. In the first Se site, Se(7) is bonded in a 5-coordinate geometry to two equivalent Cs(2), two equivalent Cs(3), and one Nb(1) atom. In the second Se site, Se(8) is bonded in a distorted single-bond geometry to one Cs(1), one Cs(3), two equivalent Cs(2), and one Nb(2) atom. In the third Se site, Se(9) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(3), one Nb(1), one Nb(2), and one Se(11) atom. The Se(9)-Se(11) bond length is 2.40 Å. In the fourth Se site, Se(10) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(2), one Nb(1), one Nb(2), and one Se(2) atom. The Se(10)-Se(2) bond length is 2.38 Å. In the fifth Se site, Se(11) is bonded in a 4-coordinate geometry to one Cs(2), one Cs(3), one Nb(1), and one Se(9) atom. In the sixth Se site, Se(1) is bonded in a 4-coordinate geometry to two equivalent Cs(1), one Nb(1), and one As(1) atom. In the seventh Se site, Se(2) is bonded in a 4-coordinate geometry to one Cs(1), one Cs(2), one Nb(2), and one Se(10) atom. In the eighth Se site, Se(3) is bonded in a distorted L-shaped geometry to one Cs(1), two equivalent Cs(3), one Nb(2), and one As(1) atom. In the ninth Se site, Se(4) is bonded in a 2-coordinate geometry to one Cs(1), one Cs(2), one Cs(3), one Nb(1), and one Nb(2) atom. In the tenth Se site, Se(5) is bonded in an L-shaped geometry to one Nb(2) and one As(1) atom. In the eleventh Se site, Se(6) is bonded in a distorted single-bond geometry to one Cs(2), two equivalent Cs(1), and one Nb(1) atom.