KPrNb4O12 crystallizes in the orthorhombic Amm2 space group. K(1) is bonded to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(4) atoms to form distorted KO12 cuboctahedra that share corners with four equivalent K(1)O12 cuboctahedra and faces with eight equivalent Nb(1)O6 octahedra. Pr(1) is bonded in a 12-coordinate geometry to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(5) atoms. Nb(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form NbO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and faces with two equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 12-20°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(1), one Pr(1), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Pr(1), and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one Pr(1), and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent K(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Pr(1) and two equivalent Nb(1) atoms.
KPrNb4O12 crystallizes in the orthorhombic Amm2 space group. K(1) is bonded to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(4) atoms to form distorted KO12 cuboctahedra that share corners with four equivalent K(1)O12 cuboctahedra and faces with eight equivalent Nb(1)O6 octahedra. Both K(1)-O(2) bond lengths are 2.62 Å. Both K(1)-O(3) bond lengths are 3.09 Å. All K(1)-O(1) bond lengths are 3.04 Å. There are two shorter (2.75 Å) and two longer (2.93 Å) K(1)-O(4) bond lengths. Pr(1) is bonded in a 12-coordinate geometry to two equivalent O(2), two equivalent O(3), four equivalent O(1), and four equivalent O(5) atoms. Both Pr(1)-O(2) bond lengths are 3.14 Å. Both Pr(1)-O(3) bond lengths are 2.55 Å. All Pr(1)-O(1) bond lengths are 2.58 Å. There are two shorter (2.73 Å) and two longer (2.97 Å) Pr(1)-O(5) bond lengths. Nb(1) is bonded to one O(2), one O(3), one O(4), one O(5), and two equivalent O(1) atoms to form NbO6 octahedra that share corners with six equivalent Nb(1)O6 octahedra and faces with two equivalent K(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 12-20°. The Nb(1)-O(2) bond length is 1.98 Å. The Nb(1)-O(3) bond length is 2.03 Å. The Nb(1)-O(4) bond length is 1.99 Å. The Nb(1)-O(5) bond length is 2.03 Å. There is one shorter (1.91 Å) and one longer (2.19 Å) Nb(1)-O(1) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(1), one Pr(1), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one K(1), one Pr(1), and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one Pr(1), and two equivalent Nb(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent K(1) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Pr(1) and two equivalent Nb(1) atoms.