Be17Ta2 crystallizes in the trigonal R-3m space group. There are four inequivalent Be sites. In the first Be site, Be(1) is bonded in a 14-coordinate geometry to one Be(1), three equivalent Be(2), three equivalent Be(4), six equivalent Be(3), and one Ta(1) atom. In the second Be site, Be(2) is bonded to two equivalent Be(1), four equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with four equivalent Be(3)Ta2Be10 cuboctahedra, edges with six equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with six equivalent Be(4)Ta3Be9 cuboctahedra, and faces with eight equivalent Be(3)Ta2Be10 cuboctahedra. In the third Be site, Be(3) is bonded to two equivalent Be(1), two equivalent Be(2), two equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(4)Ta3Be9 cuboctahedra, corners with twelve equivalent Be(3)Ta2Be10 cuboctahedra,  an edgeedge with one Be(3)Ta2Be10 cuboctahedra, edges with two equivalent Be(2)Ta2Be10 cuboctahedra, edges with two equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(3)Ta2Be10 cuboctahedra, and faces with ten equivalent Be(4)Ta3Be9 cuboctahedra. In the fourth Be site, Be(4) is bonded to one Be(1), two equivalent Be(2), two equivalent Be(4), four equivalent Be(3), and three equivalent Ta(1) atoms to form distorted BeTa3Be9 cuboctahedra that share corners with five equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with two equivalent Be(3)Ta2Be10 cuboctahedra, edges with three equivalent Be(2)Ta2Be10 cuboctahedra, edges with five equivalent Be(4)Ta3Be9 cuboctahedra, faces with three equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(4)Ta3Be9 cuboctahedra, and faces with ten equivalent Be(3)Ta2Be10 cuboctahedra. Ta(1) is bonded in a 19-coordinate geometry to one Be(1), three equivalent Be(2), six equivalent Be(3), and nine equivalent Be(4) atoms.
Be17Ta2 crystallizes in the trigonal R-3m space group. There are four inequivalent Be sites. In the first Be site, Be(1) is bonded in a 14-coordinate geometry to one Be(1), three equivalent Be(2), three equivalent Be(4), six equivalent Be(3), and one Ta(1) atom. The Be(1)-Be(1) bond length is 2.12 Å. All Be(1)-Be(2) bond lengths are 2.24 Å. All Be(1)-Be(4) bond lengths are 2.32 Å. All Be(1)-Be(3) bond lengths are 2.42 Å. The Be(1)-Ta(1) bond length is 2.58 Å. In the second Be site, Be(2) is bonded to two equivalent Be(1), four equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with four equivalent Be(3)Ta2Be10 cuboctahedra, edges with six equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with six equivalent Be(4)Ta3Be9 cuboctahedra, and faces with eight equivalent Be(3)Ta2Be10 cuboctahedra. All Be(2)-Be(3) bond lengths are 2.10 Å. All Be(2)-Be(4) bond lengths are 2.14 Å. Both Be(2)-Ta(1) bond lengths are 2.82 Å. In the third Be site, Be(3) is bonded to two equivalent Be(1), two equivalent Be(2), two equivalent Be(3), four equivalent Be(4), and two equivalent Ta(1) atoms to form distorted BeTa2Be10 cuboctahedra that share corners with four equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(4)Ta3Be9 cuboctahedra, corners with twelve equivalent Be(3)Ta2Be10 cuboctahedra,  an edgeedge with one Be(3)Ta2Be10 cuboctahedra, edges with two equivalent Be(2)Ta2Be10 cuboctahedra, edges with two equivalent Be(4)Ta3Be9 cuboctahedra, faces with four equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(3)Ta2Be10 cuboctahedra, and faces with ten equivalent Be(4)Ta3Be9 cuboctahedra. Both Be(3)-Be(3) bond lengths are 2.17 Å. There are two shorter (2.21 Å) and two longer (2.24 Å) Be(3)-Be(4) bond lengths. Both Be(3)-Ta(1) bond lengths are 2.60 Å. In the fourth Be site, Be(4) is bonded to one Be(1), two equivalent Be(2), two equivalent Be(4), four equivalent Be(3), and three equivalent Ta(1) atoms to form distorted BeTa3Be9 cuboctahedra that share corners with five equivalent Be(2)Ta2Be10 cuboctahedra, corners with eight equivalent Be(3)Ta2Be10 cuboctahedra, corners with ten equivalent Be(4)Ta3Be9 cuboctahedra, edges with two equivalent Be(3)Ta2Be10 cuboctahedra, edges with three equivalent Be(2)Ta2Be10 cuboctahedra, edges with five equivalent Be(4)Ta3Be9 cuboctahedra, faces with three equivalent Be(2)Ta2Be10 cuboctahedra, faces with seven equivalent Be(4)Ta3Be9 cuboctahedra, and faces with ten equivalent Be(3)Ta2Be10 cuboctahedra. Both Be(4)-Be(4) bond lengths are 2.10 Å. There is one shorter (2.62 Å) and two longer (2.77 Å) Be(4)-Ta(1) bond lengths. Ta(1) is bonded in a 19-coordinate geometry to one Be(1), three equivalent Be(2), six equivalent Be(3), and nine equivalent Be(4) atoms.