NiAs2 is Marcasite structured and crystallizes in the orthorhombic Pnnm space group. Ni(1) is bonded to six equivalent As(1) atoms to form NiAs6 octahedra that share corners with eight equivalent Ni(1)As6 octahedra, corners with six equivalent As(1)Ni3As tetrahedra, and edges with two equivalent Ni(1)As6 octahedra. The corner-sharing octahedral tilt angles are 58°. As(1) is bonded to three equivalent Ni(1) and one As(1) atom to form distorted AsNi3As tetrahedra that share corners with three equivalent Ni(1)As6 octahedra, corners with thirteen equivalent As(1)Ni3As tetrahedra, and  an edgeedge with one As(1)Ni3As tetrahedra. The corner-sharing octahedral tilt angles range from 74-77°.
NiAs2 is Marcasite structured and crystallizes in the orthorhombic Pnnm space group. Ni(1) is bonded to six equivalent As(1) atoms to form NiAs6 octahedra that share corners with eight equivalent Ni(1)As6 octahedra, corners with six equivalent As(1)Ni3As tetrahedra, and edges with two equivalent Ni(1)As6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are two shorter (2.35 Å) and four longer (2.39 Å) Ni(1)-As(1) bond lengths. As(1) is bonded to three equivalent Ni(1) and one As(1) atom to form distorted AsNi3As tetrahedra that share corners with three equivalent Ni(1)As6 octahedra, corners with thirteen equivalent As(1)Ni3As tetrahedra, and  an edgeedge with one As(1)Ni3As tetrahedra. The corner-sharing octahedral tilt angles range from 74-77°. The As(1)-As(1) bond length is 2.45 Å.