Cs4Hf3Se14 crystallizes in the monoclinic C2/c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 10-coordinate geometry to one Se(1), one Se(3), one Se(4), two equivalent Se(5), two equivalent Se(7), and three equivalent Se(6) atoms. In the second Cs site, Cs(2) is bonded in a 10-coordinate geometry to one Se(4), one Se(5), one Se(6), one Se(7), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to one Se(2), one Se(3), one Se(4), one Se(6), one Se(7), and two equivalent Se(5) atoms to form distorted HfSe7 pentagonal bipyramids that share  an edgeedge with one Hf(1)Se7 pentagonal bipyramid and  a faceface with one Hf(2)Se8 hexagonal bipyramid. In the second Hf site, Hf(2) is bonded to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form distorted face-sharing HfSe8 hexagonal bipyramids. There are seven inequivalent Se sites. In the first Se site, Se(2) is bonded in a 2-coordinate geometry to two equivalent Cs(2), one Hf(1), one Hf(2), and one Se(7) atom. In the second Se site, Se(3) is bonded in a 2-coordinate geometry to one Cs(1), two equivalent Cs(2), one Hf(1), and one Hf(2) atom. In the third Se site, Se(4) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(2), one Hf(1), one Hf(2), one Se(1), and one Se(7) atom. In the fourth Se site, Se(5) is bonded in a 5-coordinate geometry to one Cs(2), two equivalent Cs(1), and two equivalent Hf(1) atoms. In the fifth Se site, Se(6) is bonded in a 1-coordinate geometry to one Cs(2), three equivalent Cs(1), and one Hf(1) atom. In the sixth Se site, Se(7) is bonded in a 6-coordinate geometry to one Cs(2), two equivalent Cs(1), one Hf(1), one Se(2), and one Se(4) atom. In the seventh Se site, Se(1) is bonded in a 1-coordinate geometry to one Cs(1), two equivalent Cs(2), one Hf(2), and one Se(4) atom.
Cs4Hf3Se14 crystallizes in the monoclinic C2/c space group. There are two inequivalent Cs sites. In the first Cs site, Cs(1) is bonded in a 10-coordinate geometry to one Se(1), one Se(3), one Se(4), two equivalent Se(5), two equivalent Se(7), and three equivalent Se(6) atoms. The Cs(1)-Se(1) bond length is 3.81 Å. The Cs(1)-Se(3) bond length is 4.05 Å. The Cs(1)-Se(4) bond length is 3.75 Å. There is one shorter (3.63 Å) and one longer (4.14 Å) Cs(1)-Se(5) bond length. There is one shorter (3.78 Å) and one longer (4.01 Å) Cs(1)-Se(7) bond length. There are a spread of Cs(1)-Se(6) bond distances ranging from 3.88-4.18 Å. In the second Cs site, Cs(2) is bonded in a 10-coordinate geometry to one Se(4), one Se(5), one Se(6), one Se(7), two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. The Cs(2)-Se(4) bond length is 3.77 Å. The Cs(2)-Se(5) bond length is 4.01 Å. The Cs(2)-Se(6) bond length is 3.70 Å. The Cs(2)-Se(7) bond length is 3.85 Å. There is one shorter (3.72 Å) and one longer (3.90 Å) Cs(2)-Se(1) bond length. There is one shorter (3.74 Å) and one longer (4.21 Å) Cs(2)-Se(2) bond length. There is one shorter (4.00 Å) and one longer (4.11 Å) Cs(2)-Se(3) bond length. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to one Se(2), one Se(3), one Se(4), one Se(6), one Se(7), and two equivalent Se(5) atoms to form distorted HfSe7 pentagonal bipyramids that share  an edgeedge with one Hf(1)Se7 pentagonal bipyramid and  a faceface with one Hf(2)Se8 hexagonal bipyramid. The Hf(1)-Se(2) bond length is 2.80 Å. The Hf(1)-Se(3) bond length is 2.75 Å. The Hf(1)-Se(4) bond length is 2.86 Å. The Hf(1)-Se(6) bond length is 2.65 Å. The Hf(1)-Se(7) bond length is 2.73 Å. There is one shorter (2.57 Å) and one longer (2.72 Å) Hf(1)-Se(5) bond length. In the second Hf site, Hf(2) is bonded to two equivalent Se(1), two equivalent Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form distorted face-sharing HfSe8 hexagonal bipyramids. Both Hf(2)-Se(1) bond lengths are 2.71 Å. Both Hf(2)-Se(2) bond lengths are 2.77 Å. Both Hf(2)-Se(3) bond lengths are 2.82 Å. Both Hf(2)-Se(4) bond lengths are 2.71 Å. There are seven inequivalent Se sites. In the first Se site, Se(2) is bonded in a 2-coordinate geometry to two equivalent Cs(2), one Hf(1), one Hf(2), and one Se(7) atom. The Se(2)-Se(7) bond length is 2.47 Å. In the second Se site, Se(3) is bonded in a 2-coordinate geometry to one Cs(1), two equivalent Cs(2), one Hf(1), and one Hf(2) atom. In the third Se site, Se(4) is bonded in a 6-coordinate geometry to one Cs(1), one Cs(2), one Hf(1), one Hf(2), one Se(1), and one Se(7) atom. The Se(4)-Se(1) bond length is 2.51 Å. The Se(4)-Se(7) bond length is 2.86 Å. In the fourth Se site, Se(5) is bonded in a 5-coordinate geometry to one Cs(2), two equivalent Cs(1), and two equivalent Hf(1) atoms. In the fifth Se site, Se(6) is bonded in a 1-coordinate geometry to one Cs(2), three equivalent Cs(1), and one Hf(1) atom. In the sixth Se site, Se(7) is bonded in a 6-coordinate geometry to one Cs(2), two equivalent Cs(1), one Hf(1), one Se(2), and one Se(4) atom. In the seventh Se site, Se(1) is bonded in a 1-coordinate geometry to one Cs(1), two equivalent Cs(2), one Hf(2), and one Se(4) atom.