Cs4Nb2Si8O23 crystallizes in the triclinic P-1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 12-coordinate geometry to one O(10), one O(11), one O(5), one O(6), one O(7), two equivalent O(2), two equivalent O(3), and three equivalent O(4) atoms. In the second Cs site, Cs(2) is bonded in a 14-coordinate geometry to one O(11), one O(12), one O(3), one O(5), one O(6), one O(7), two equivalent O(1), two equivalent O(10), two equivalent O(8), and two equivalent O(9) atoms. Nb(1) is bonded to one O(11), one O(3), one O(4), one O(6), one O(7), and one O(8) atom to form NbO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-40°. In the second Si site, Si(2) is bonded to one O(1), one O(10), one O(2), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. In the third Si site, Si(3) is bonded to one O(1), one O(12), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 8°. In the fourth Si site, Si(4) is bonded to one O(10), one O(11), one O(5), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Cs(2), one Si(2), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Cs(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cs(2), two equivalent Cs(1), and one Nb(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to three equivalent Cs(1), one Nb(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), one Si(1), and one Si(4) atom. In the sixth O site, O(6) is bonded in a 1-coordinate geometry to one Cs(1), one Cs(2), one Nb(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), one Nb(1), and one Si(1) atom. In the eighth O site, O(8) is bonded in a linear geometry to two equivalent Cs(2), one Nb(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to two equivalent Cs(2), one Si(3), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Cs(1), two equivalent Cs(2), one Si(2), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), one Nb(1), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a linear geometry to two equivalent Cs(2) and two equivalent Si(3) atoms.
Cs4Nb2Si8O23 crystallizes in the triclinic P-1 space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 12-coordinate geometry to one O(10), one O(11), one O(5), one O(6), one O(7), two equivalent O(2), two equivalent O(3), and three equivalent O(4) atoms. The Cs(1)-O(10) bond length is 3.70 Å. The Cs(1)-O(11) bond length is 3.48 Å. The Cs(1)-O(5) bond length is 3.19 Å. The Cs(1)-O(6) bond length is 3.03 Å. The Cs(1)-O(7) bond length is 3.46 Å. There is one shorter (3.29 Å) and one longer (3.74 Å) Cs(1)-O(2) bond length. There is one shorter (3.09 Å) and one longer (3.13 Å) Cs(1)-O(3) bond length. There are a spread of Cs(1)-O(4) bond distances ranging from 3.40-3.61 Å. In the second Cs site, Cs(2) is bonded in a 14-coordinate geometry to one O(11), one O(12), one O(3), one O(5), one O(6), one O(7), two equivalent O(1), two equivalent O(10), two equivalent O(8), and two equivalent O(9) atoms. The Cs(2)-O(11) bond length is 3.43 Å. The Cs(2)-O(12) bond length is 3.82 Å. The Cs(2)-O(3) bond length is 3.04 Å. The Cs(2)-O(5) bond length is 3.36 Å. The Cs(2)-O(6) bond length is 3.23 Å. The Cs(2)-O(7) bond length is 3.35 Å. There is one shorter (3.35 Å) and one longer (3.36 Å) Cs(2)-O(1) bond length. There is one shorter (3.50 Å) and one longer (3.76 Å) Cs(2)-O(10) bond length. Both Cs(2)-O(8) bond lengths are 3.56 Å. There is one shorter (3.23 Å) and one longer (3.79 Å) Cs(2)-O(9) bond length. Nb(1) is bonded to one O(11), one O(3), one O(4), one O(6), one O(7), and one O(8) atom to form NbO6 octahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The Nb(1)-O(11) bond length is 2.08 Å. The Nb(1)-O(3) bond length is 1.79 Å. The Nb(1)-O(4) bond length is 2.06 Å. The Nb(1)-O(6) bond length is 2.23 Å. The Nb(1)-O(7) bond length is 2.02 Å. The Nb(1)-O(8) bond length is 2.05 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Nb(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-40°. The Si(1)-O(2) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.66 Å. The Si(1)-O(7) bond length is 1.62 Å. In the second Si site, Si(2) is bonded to one O(1), one O(10), one O(2), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. The Si(2)-O(1) bond length is 1.65 Å. The Si(2)-O(10) bond length is 1.66 Å. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(6) bond length is 1.59 Å. In the third Si site, Si(3) is bonded to one O(1), one O(12), one O(8), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles are 8°. The Si(3)-O(1) bond length is 1.65 Å. The Si(3)-O(12) bond length is 1.63 Å. The Si(3)-O(8) bond length is 1.60 Å. The Si(3)-O(9) bond length is 1.65 Å. In the fourth Si site, Si(4) is bonded to one O(10), one O(11), one O(5), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Nb(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 40°. The Si(4)-O(10) bond length is 1.65 Å. The Si(4)-O(11) bond length is 1.61 Å. The Si(4)-O(5) bond length is 1.64 Å. The Si(4)-O(9) bond length is 1.65 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Cs(2), one Si(2), and one Si(3) atom. In the second O site, O(2) is bonded in a distorted linear geometry to two equivalent Cs(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cs(2), two equivalent Cs(1), and one Nb(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to three equivalent Cs(1), one Nb(1), and one Si(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), one Si(1), and one Si(4) atom. In the sixth O site, O(6) is bonded in a 1-coordinate geometry to one Cs(1), one Cs(2), one Nb(1), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), one Nb(1), and one Si(1) atom. In the eighth O site, O(8) is bonded in a linear geometry to two equivalent Cs(2), one Nb(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to two equivalent Cs(2), one Si(3), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Cs(1), two equivalent Cs(2), one Si(2), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a distorted bent 150 degrees geometry to one Cs(1), one Cs(2), one Nb(1), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a linear geometry to two equivalent Cs(2) and two equivalent Si(3) atoms.