NiAs2 is Pyrite-like structured and crystallizes in the orthorhombic Pbca space group. Ni(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form NiAs6 octahedra that share corners with ten equivalent Ni(1)As6 octahedra, corners with three equivalent As(1)Ni3As tetrahedra, corners with three equivalent As(2)Ni3As tetrahedra, and  an edgeedge with one Ni(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 55-65°. There are two inequivalent As sites. In the first As site, As(1) is bonded to three equivalent Ni(1) and one As(2) atom to form distorted AsNi3As tetrahedra that share corners with three equivalent Ni(1)As6 octahedra, corners with six equivalent As(1)Ni3As tetrahedra, and corners with nine equivalent As(2)Ni3As tetrahedra. The corner-sharing octahedral tilt angles range from 71-80°. In the second As site, As(2) 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 four equivalent As(2)Ni3As tetrahedra, corners with nine equivalent As(1)Ni3As tetrahedra, and  an edgeedge with one As(2)Ni3As tetrahedra. The corner-sharing octahedral tilt angles range from 75-83°.
NiAs2 is Pyrite-like structured and crystallizes in the orthorhombic Pbca space group. Ni(1) is bonded to three equivalent As(1) and three equivalent As(2) atoms to form NiAs6 octahedra that share corners with ten equivalent Ni(1)As6 octahedra, corners with three equivalent As(1)Ni3As tetrahedra, corners with three equivalent As(2)Ni3As tetrahedra, and  an edgeedge with one Ni(1)As6 octahedra. The corner-sharing octahedral tilt angles range from 55-65°. There are a spread of Ni(1)-As(1) bond distances ranging from 2.36-2.40 Å. There are two shorter (2.37 Å) and one longer (2.38 Å) Ni(1)-As(2) bond length. There are two inequivalent As sites. In the first As site, As(1) is bonded to three equivalent Ni(1) and one As(2) atom to form distorted AsNi3As tetrahedra that share corners with three equivalent Ni(1)As6 octahedra, corners with six equivalent As(1)Ni3As tetrahedra, and corners with nine equivalent As(2)Ni3As tetrahedra. The corner-sharing octahedral tilt angles range from 71-80°. The As(1)-As(2) bond length is 2.45 Å. In the second As site, As(2) 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 four equivalent As(2)Ni3As tetrahedra, corners with nine equivalent As(1)Ni3As tetrahedra, and  an edgeedge with one As(2)Ni3As tetrahedra. The corner-sharing octahedral tilt angles range from 75-83°.