Ta3Cu is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to four equivalent Ta(1), four equivalent Ta(2), and four equivalent Cu(1) atoms to form distorted TaTa8Cu4 cuboctahedra that share corners with twelve equivalent Ta(1)Ta8Cu4 cuboctahedra, edges with eight equivalent Ta(1)Ta8Cu4 cuboctahedra, edges with eight equivalent Ta(2)Ta8Cu4 cuboctahedra, edges with eight equivalent Cu(1)Ta12 cuboctahedra, faces with four equivalent Ta(2)Ta8Cu4 cuboctahedra, faces with four equivalent Cu(1)Ta12 cuboctahedra, and faces with ten equivalent Ta(1)Ta8Cu4 cuboctahedra. In the second Ta site, Ta(2) is bonded to eight equivalent Ta(1) and four equivalent Cu(1) atoms to form distorted TaTa8Cu4 cuboctahedra that share corners with four equivalent Ta(2)Ta8Cu4 cuboctahedra, corners with eight equivalent Cu(1)Ta12 cuboctahedra, edges with eight equivalent Ta(2)Ta8Cu4 cuboctahedra, edges with sixteen equivalent Ta(1)Ta8Cu4 cuboctahedra, faces with four equivalent Ta(2)Ta8Cu4 cuboctahedra, faces with six equivalent Cu(1)Ta12 cuboctahedra, and faces with eight equivalent Ta(1)Ta8Cu4 cuboctahedra. Cu(1) is bonded to four equivalent Ta(2) and eight equivalent Ta(1) atoms to form CuTa12 cuboctahedra that share corners with four equivalent Cu(1)Ta12 cuboctahedra, corners with eight equivalent Ta(2)Ta8Cu4 cuboctahedra, edges with eight equivalent Cu(1)Ta12 cuboctahedra, edges with sixteen equivalent Ta(1)Ta8Cu4 cuboctahedra, faces with four equivalent Cu(1)Ta12 cuboctahedra, faces with six equivalent Ta(2)Ta8Cu4 cuboctahedra, and faces with eight equivalent Ta(1)Ta8Cu4 cuboctahedra.
Ta3Cu is beta Cu3Ti-like structured and crystallizes in the tetragonal I4/mmm space group. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to four equivalent Ta(1), four equivalent Ta(2), and four equivalent Cu(1) atoms to form distorted TaTa8Cu4 cuboctahedra that share corners with twelve equivalent Ta(1)Ta8Cu4 cuboctahedra, edges with eight equivalent Ta(1)Ta8Cu4 cuboctahedra, edges with eight equivalent Ta(2)Ta8Cu4 cuboctahedra, edges with eight equivalent Cu(1)Ta12 cuboctahedra, faces with four equivalent Ta(2)Ta8Cu4 cuboctahedra, faces with four equivalent Cu(1)Ta12 cuboctahedra, and faces with ten equivalent Ta(1)Ta8Cu4 cuboctahedra. All Ta(1)-Ta(1) bond lengths are 2.84 Å. All Ta(1)-Ta(2) bond lengths are 2.91 Å. All Ta(1)-Cu(1) bond lengths are 2.91 Å. In the second Ta site, Ta(2) is bonded to eight equivalent Ta(1) and four equivalent Cu(1) atoms to form distorted TaTa8Cu4 cuboctahedra that share corners with four equivalent Ta(2)Ta8Cu4 cuboctahedra, corners with eight equivalent Cu(1)Ta12 cuboctahedra, edges with eight equivalent Ta(2)Ta8Cu4 cuboctahedra, edges with sixteen equivalent Ta(1)Ta8Cu4 cuboctahedra, faces with four equivalent Ta(2)Ta8Cu4 cuboctahedra, faces with six equivalent Cu(1)Ta12 cuboctahedra, and faces with eight equivalent Ta(1)Ta8Cu4 cuboctahedra. All Ta(2)-Cu(1) bond lengths are 2.84 Å. Cu(1) is bonded to four equivalent Ta(2) and eight equivalent Ta(1) atoms to form CuTa12 cuboctahedra that share corners with four equivalent Cu(1)Ta12 cuboctahedra, corners with eight equivalent Ta(2)Ta8Cu4 cuboctahedra, edges with eight equivalent Cu(1)Ta12 cuboctahedra, edges with sixteen equivalent Ta(1)Ta8Cu4 cuboctahedra, faces with four equivalent Cu(1)Ta12 cuboctahedra, faces with six equivalent Ta(2)Ta8Cu4 cuboctahedra, and faces with eight equivalent Ta(1)Ta8Cu4 cuboctahedra.