NpCo3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Np(1) is bonded to twelve equivalent Co(1) atoms to form NpCo12 cuboctahedra that share corners with six equivalent Np(1)Co12 cuboctahedra, corners with twelve equivalent Co(1)Np4Co8 cuboctahedra, edges with eighteen equivalent Co(1)Np4Co8 cuboctahedra, faces with eight equivalent Np(1)Co12 cuboctahedra, and faces with twelve equivalent Co(1)Np4Co8 cuboctahedra. Co(1) is bonded to four equivalent Np(1) and eight equivalent Co(1) atoms to form distorted CoNp4Co8 cuboctahedra that share corners with four equivalent Np(1)Co12 cuboctahedra, corners with fourteen equivalent Co(1)Np4Co8 cuboctahedra, edges with six equivalent Np(1)Co12 cuboctahedra, edges with twelve equivalent Co(1)Np4Co8 cuboctahedra, faces with four equivalent Np(1)Co12 cuboctahedra, and faces with sixteen equivalent Co(1)Np4Co8 cuboctahedra.
NpCo3 is beta Cu3Ti-like structured and crystallizes in the hexagonal P6_3/mmc space group. Np(1) is bonded to twelve equivalent Co(1) atoms to form NpCo12 cuboctahedra that share corners with six equivalent Np(1)Co12 cuboctahedra, corners with twelve equivalent Co(1)Np4Co8 cuboctahedra, edges with eighteen equivalent Co(1)Np4Co8 cuboctahedra, faces with eight equivalent Np(1)Co12 cuboctahedra, and faces with twelve equivalent Co(1)Np4Co8 cuboctahedra. There are six shorter (2.61 Å) and six longer (2.68 Å) Np(1)-Co(1) bond lengths. Co(1) is bonded to four equivalent Np(1) and eight equivalent Co(1) atoms to form distorted CoNp4Co8 cuboctahedra that share corners with four equivalent Np(1)Co12 cuboctahedra, corners with fourteen equivalent Co(1)Np4Co8 cuboctahedra, edges with six equivalent Np(1)Co12 cuboctahedra, edges with twelve equivalent Co(1)Np4Co8 cuboctahedra, faces with four equivalent Np(1)Co12 cuboctahedra, and faces with sixteen equivalent Co(1)Np4Co8 cuboctahedra. There are a spread of Co(1)-Co(1) bond distances ranging from 2.54-2.68 Å.