KYP2O7 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded in a 10-coordinate geometry to two equivalent O(3) and eight equivalent O(1) atoms. Y(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form YO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent Y(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-43°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1), one Y(1), and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Y(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1) and two equivalent P(1) atoms.
KYP2O7 crystallizes in the orthorhombic Cmcm space group. K(1) is bonded in a 10-coordinate geometry to two equivalent O(3) and eight equivalent O(1) atoms. Both K(1)-O(3) bond lengths are 2.97 Å. There are four shorter (3.02 Å) and four longer (3.21 Å) K(1)-O(1) bond lengths. Y(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form YO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. Both Y(1)-O(2) bond lengths are 2.21 Å. All Y(1)-O(1) bond lengths are 2.25 Å. P(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent Y(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-43°. The P(1)-O(2) bond length is 1.50 Å. The P(1)-O(3) bond length is 1.63 Å. Both P(1)-O(1) bond lengths are 1.51 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to two equivalent K(1), one Y(1), and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Y(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1) and two equivalent P(1) atoms.