BC7 crystallizes in the cubic P-43m space group. B(1) is bonded to four equivalent C(2) atoms to form BC4 tetrahedra that share corners with twelve equivalent C(1)C4 tetrahedra. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent C(2) atoms to form CC4 tetrahedra that share corners with four equivalent B(1)C4 tetrahedra and corners with eight equivalent C(1)C4 tetrahedra. In the second C site, C(2) is bonded to one B(1) and three equivalent C(1) atoms to form distorted corner-sharing CBC3 tetrahedra.
BC7 crystallizes in the cubic P-43m space group. B(1) is bonded to four equivalent C(2) atoms to form BC4 tetrahedra that share corners with twelve equivalent C(1)C4 tetrahedra. All B(1)-C(2) bond lengths are 1.60 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded to four equivalent C(2) atoms to form CC4 tetrahedra that share corners with four equivalent B(1)C4 tetrahedra and corners with eight equivalent C(1)C4 tetrahedra. All C(1)-C(2) bond lengths are 1.56 Å. In the second C site, C(2) is bonded to one B(1) and three equivalent C(1) atoms to form distorted corner-sharing CBC3 tetrahedra.