Ta2Co crystallizes in the hexagonal P6_3/mcm space group. There are five inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to six Ta(2,2,2,2) and six equivalent Co(1) atoms to form TaTa6Co6 cuboctahedra that share corners with eighteen equivalent Co(1)Ta9Co3 cuboctahedra; edges with six equivalent Ta(1)Ta6Co6 cuboctahedra; edges with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; faces with two equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six equivalent Co(1)Ta9Co3 cuboctahedra; and faces with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra. In the second Ta site, Ta(2) is bonded to two equivalent Ta(1), six equivalent Ta(2), and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six equivalent Ta(2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. In the third Ta site, Ta(2) is bonded to two equivalent Ta(1); six Ta(2,2); and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six Ta(2,2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. In the fourth Ta site, Ta(2) is bonded to two equivalent Ta(1), six equivalent Ta(2), and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six equivalent Ta(2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. In the fifth Ta site, Ta(2) is bonded to two equivalent Ta(1); six Ta(2,2); and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six Ta(2,2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. Co(1) is bonded to three equivalent Ta(1); six Ta(2,2,2,2); and three equivalent Co(1) atoms to form distorted CoTa9Co3 cuboctahedra that share corners with nine equivalent Ta(1)Ta6Co6 cuboctahedra; corners with nine equivalent Co(1)Ta9Co3 cuboctahedra; edges with six equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; faces with three equivalent Ta(1)Ta6Co6 cuboctahedra; faces with five equivalent Co(1)Ta9Co3 cuboctahedra; and faces with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra.
Ta2Co crystallizes in the hexagonal P6_3/mcm space group. There are five inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to six Ta(2,2,2,2) and six equivalent Co(1) atoms to form TaTa6Co6 cuboctahedra that share corners with eighteen equivalent Co(1)Ta9Co3 cuboctahedra; edges with six equivalent Ta(1)Ta6Co6 cuboctahedra; edges with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; faces with two equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six equivalent Co(1)Ta9Co3 cuboctahedra; and faces with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra. All Ta(1)-Ta(2,2,2,2) bond lengths are 2.84 Å. All Ta(1)-Co(1) bond lengths are 2.87 Å. In the second Ta site, Ta(2) is bonded to two equivalent Ta(1), six equivalent Ta(2), and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six equivalent Ta(2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. There are four shorter (2.81 Å) and two longer (2.99 Å) Ta(2)-Ta(2) bond lengths. All Ta(2)-Co(1) bond lengths are 2.77 Å. In the third Ta site, Ta(2) is bonded to two equivalent Ta(1); six Ta(2,2); and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six Ta(2,2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. There are two shorter (2.81 Å) and one longer (2.99 Å) Ta(2)-Ta(2) bond length. All Ta(2)-Co(1) bond lengths are 2.77 Å. In the fourth Ta site, Ta(2) is bonded to two equivalent Ta(1), six equivalent Ta(2), and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six equivalent Ta(2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. There are four shorter (2.81 Å) and two longer (2.99 Å) Ta(2)-Ta(2) bond lengths. All Ta(2)-Co(1) bond lengths are 2.77 Å. In the fifth Ta site, Ta(2) is bonded to two equivalent Ta(1); six Ta(2,2); and four equivalent Co(1) atoms to form distorted TaTa8Co4 cuboctahedra that share corners with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; edges with four equivalent Ta(1)Ta6Co6 cuboctahedra; edges with eight equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2)Ta8Co4 cuboctahedra; faces with four equivalent Ta(1)Ta6Co6 cuboctahedra; faces with six Ta(2,2)Ta8Co4 cuboctahedra; and faces with eight equivalent Co(1)Ta9Co3 cuboctahedra. There are two shorter (2.81 Å) and one longer (2.99 Å) Ta(2)-Ta(2) bond length. All Ta(2)-Co(1) bond lengths are 2.77 Å. Co(1) is bonded to three equivalent Ta(1); six Ta(2,2,2,2); and three equivalent Co(1) atoms to form distorted CoTa9Co3 cuboctahedra that share corners with nine equivalent Ta(1)Ta6Co6 cuboctahedra; corners with nine equivalent Co(1)Ta9Co3 cuboctahedra; edges with six equivalent Co(1)Ta9Co3 cuboctahedra; edges with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra; faces with three equivalent Ta(1)Ta6Co6 cuboctahedra; faces with five equivalent Co(1)Ta9Co3 cuboctahedra; and faces with twelve Ta(2,2,2,2)Ta8Co4 cuboctahedra. All Co(1)-Co(1) bond lengths are 2.87 Å.