KNiAsO4 crystallizes in the trigonal R-3 space group. K(1) is bonded in a 7-coordinate geometry to three equivalent O(2) and four equivalent O(1) atoms. Ni(1) is bonded to six equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent As(1)O4 tetrahedra and edges with three equivalent Ni(1)O6 octahedra. As(1) is bonded to one O(1) and three equivalent O(2) atoms to form AsO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-56°. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent K(1) and one As(1) atom to form a mixture of distorted edge and corner-sharing OK4As trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(1), two equivalent Ni(1), and one As(1) atom.
KNiAsO4 crystallizes in the trigonal R-3 space group. K(1) is bonded in a 7-coordinate geometry to three equivalent O(2) and four equivalent O(1) atoms. All K(1)-O(2) bond lengths are 2.88 Å. There is one shorter (2.66 Å) and three longer (2.92 Å) K(1)-O(1) bond lengths. Ni(1) is bonded to six equivalent O(2) atoms to form NiO6 octahedra that share corners with six equivalent As(1)O4 tetrahedra and edges with three equivalent Ni(1)O6 octahedra. There are three shorter (2.08 Å) and three longer (2.10 Å) Ni(1)-O(2) bond lengths. As(1) is bonded to one O(1) and three equivalent O(2) atoms to form AsO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 54-56°. The As(1)-O(1) bond length is 1.70 Å. All As(1)-O(2) bond lengths are 1.74 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent K(1) and one As(1) atom to form a mixture of distorted edge and corner-sharing OK4As trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one K(1), two equivalent Ni(1), and one As(1) atom.