NpAs3 crystallizes in the tetragonal I4/mmm space group. Np(1) is bonded to four equivalent As(2) and eight equivalent As(1) atoms to form a mixture of corner, edge, and face-sharing NpAs12 cuboctahedra. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 8-coordinate geometry to four equivalent Np(1) and four equivalent As(1) atoms. In the second As site, As(2) is bonded in a square co-planar geometry to four equivalent Np(1) atoms.
NpAs3 crystallizes in the tetragonal I4/mmm space group. Np(1) is bonded to four equivalent As(2) and eight equivalent As(1) atoms to form a mixture of corner, edge, and face-sharing NpAs12 cuboctahedra. All Np(1)-As(2) bond lengths are 2.86 Å. All Np(1)-As(1) bond lengths are 3.16 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded in a 8-coordinate geometry to four equivalent Np(1) and four equivalent As(1) atoms. All As(1)-As(1) bond lengths are 2.86 Å. In the second As site, As(2) is bonded in a square co-planar geometry to four equivalent Np(1) atoms.