K2PSe3 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. In the second K site, K(2) is bonded in a 8-coordinate geometry to one P(1), one Se(1), one Se(3), one Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. In the third K site, K(3) is bonded in a 6-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. In the fourth K site, K(4) is bonded in a 8-coordinate geometry to one P(2), one Se(2), one Se(3), one Se(4), one Se(5), one Se(6), and two equivalent Se(1) atoms. There are two inequivalent P sites. In the first P site, P(1) is bonded in a distorted trigonal non-coplanar geometry to one K(2), one Se(1), one Se(2), and one Se(3) atom. In the second P site, P(2) is bonded in a distorted trigonal non-coplanar geometry to one K(4), one Se(4), one Se(5), and one Se(6) atom. There are six inequivalent Se sites. In the first Se site, Se(3) is bonded in a 5-coordinate geometry to one K(2), one K(4), two equivalent K(3), and one P(1) atom. In the second Se site, Se(4) is bonded in a 5-coordinate geometry to one K(2), one K(4), two equivalent K(1), and one P(2) atom. In the third Se site, Se(5) is bonded in a 6-coordinate geometry to one K(4), two equivalent K(1), two equivalent K(2), and one P(2) atom. In the fourth Se site, Se(6) is bonded in a 6-coordinate geometry to one K(4), two equivalent K(1), two equivalent K(2), and one P(2) atom. In the fifth Se site, Se(1) is bonded in a 6-coordinate geometry to one K(2), two equivalent K(3), two equivalent K(4), and one P(1) atom. In the sixth Se site, Se(2) is bonded in a 4-coordinate geometry to one K(4), two equivalent K(3), and one P(1) atom.
K2PSe3 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to two equivalent Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. There is one shorter (3.32 Å) and one longer (3.40 Å) K(1)-Se(4) bond length. There is one shorter (3.35 Å) and one longer (3.44 Å) K(1)-Se(5) bond length. There is one shorter (3.34 Å) and one longer (3.43 Å) K(1)-Se(6) bond length. In the second K site, K(2) is bonded in a 8-coordinate geometry to one P(1), one Se(1), one Se(3), one Se(4), two equivalent Se(5), and two equivalent Se(6) atoms. The K(2)-P(1) bond length is 3.60 Å. The K(2)-Se(1) bond length is 3.35 Å. The K(2)-Se(3) bond length is 3.35 Å. The K(2)-Se(4) bond length is 3.42 Å. There is one shorter (3.36 Å) and one longer (3.84 Å) K(2)-Se(5) bond length. There is one shorter (3.36 Å) and one longer (3.70 Å) K(2)-Se(6) bond length. In the third K site, K(3) is bonded in a 6-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. There is one shorter (3.39 Å) and one longer (3.45 Å) K(3)-Se(1) bond length. There is one shorter (3.32 Å) and one longer (3.43 Å) K(3)-Se(2) bond length. There is one shorter (3.34 Å) and one longer (3.41 Å) K(3)-Se(3) bond length. In the fourth K site, K(4) is bonded in a 8-coordinate geometry to one P(2), one Se(2), one Se(3), one Se(4), one Se(5), one Se(6), and two equivalent Se(1) atoms. The K(4)-P(2) bond length is 3.48 Å. The K(4)-Se(2) bond length is 3.41 Å. The K(4)-Se(3) bond length is 3.39 Å. The K(4)-Se(4) bond length is 3.35 Å. The K(4)-Se(5) bond length is 3.72 Å. The K(4)-Se(6) bond length is 3.53 Å. There is one shorter (3.32 Å) and one longer (3.40 Å) K(4)-Se(1) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded in a distorted trigonal non-coplanar geometry to one K(2), one Se(1), one Se(2), and one Se(3) atom. The P(1)-Se(1) bond length is 2.19 Å. The P(1)-Se(2) bond length is 2.17 Å. The P(1)-Se(3) bond length is 2.19 Å. In the second P site, P(2) is bonded in a distorted trigonal non-coplanar geometry to one K(4), one Se(4), one Se(5), and one Se(6) atom. The P(2)-Se(4) bond length is 2.19 Å. The P(2)-Se(5) bond length is 2.19 Å. The P(2)-Se(6) bond length is 2.19 Å. There are six inequivalent Se sites. In the first Se site, Se(3) is bonded in a 5-coordinate geometry to one K(2), one K(4), two equivalent K(3), and one P(1) atom. In the second Se site, Se(4) is bonded in a 5-coordinate geometry to one K(2), one K(4), two equivalent K(1), and one P(2) atom. In the third Se site, Se(5) is bonded in a 6-coordinate geometry to one K(4), two equivalent K(1), two equivalent K(2), and one P(2) atom. In the fourth Se site, Se(6) is bonded in a 6-coordinate geometry to one K(4), two equivalent K(1), two equivalent K(2), and one P(2) atom. In the fifth Se site, Se(1) is bonded in a 6-coordinate geometry to one K(2), two equivalent K(3), two equivalent K(4), and one P(1) atom. In the sixth Se site, Se(2) is bonded in a 4-coordinate geometry to one K(4), two equivalent K(3), and one P(1) atom.