NpPa3 crystallizes in the hexagonal P6_3/mmc space group. Np(1) is bonded to twelve equivalent Pa(1) atoms to form NpPa12 cuboctahedra that share corners with six equivalent Np(1)Pa12 cuboctahedra, corners with twelve equivalent Pa(1)Np4Pa8 cuboctahedra, edges with eighteen equivalent Pa(1)Np4Pa8 cuboctahedra, faces with eight equivalent Np(1)Pa12 cuboctahedra, and faces with twelve equivalent Pa(1)Np4Pa8 cuboctahedra. Pa(1) is bonded to four equivalent Np(1) and eight equivalent Pa(1) atoms to form distorted PaNp4Pa8 cuboctahedra that share corners with four equivalent Np(1)Pa12 cuboctahedra, corners with fourteen equivalent Pa(1)Np4Pa8 cuboctahedra, edges with six equivalent Np(1)Pa12 cuboctahedra, edges with twelve equivalent Pa(1)Np4Pa8 cuboctahedra, faces with four equivalent Np(1)Pa12 cuboctahedra, and faces with sixteen equivalent Pa(1)Np4Pa8 cuboctahedra.
NpPa3 crystallizes in the hexagonal P6_3/mmc space group. Np(1) is bonded to twelve equivalent Pa(1) atoms to form NpPa12 cuboctahedra that share corners with six equivalent Np(1)Pa12 cuboctahedra, corners with twelve equivalent Pa(1)Np4Pa8 cuboctahedra, edges with eighteen equivalent Pa(1)Np4Pa8 cuboctahedra, faces with eight equivalent Np(1)Pa12 cuboctahedra, and faces with twelve equivalent Pa(1)Np4Pa8 cuboctahedra. There are six shorter (3.09 Å) and six longer (3.32 Å) Np(1)-Pa(1) bond lengths. Pa(1) is bonded to four equivalent Np(1) and eight equivalent Pa(1) atoms to form distorted PaNp4Pa8 cuboctahedra that share corners with four equivalent Np(1)Pa12 cuboctahedra, corners with fourteen equivalent Pa(1)Np4Pa8 cuboctahedra, edges with six equivalent Np(1)Pa12 cuboctahedra, edges with twelve equivalent Pa(1)Np4Pa8 cuboctahedra, faces with four equivalent Np(1)Pa12 cuboctahedra, and faces with sixteen equivalent Pa(1)Np4Pa8 cuboctahedra. There are a spread of Pa(1)-Pa(1) bond distances ranging from 3.07-3.33 Å.