Materials Data on BC7 by Materials Project

Abstract

BC7 is beta beryllia-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. B3+ is bonded to four C+0.43- atoms to form BC4 tetrahedra that share corners with six equivalent BC4 tetrahedra and corners with six CC4 tetrahedra. There is one shorter (1.61 Å) and three longer (1.63 Å) B–C bond length. There are seven inequivalent C+0.43- sites. In the first C+0.43- site, C+0.43- is bonded to four C+0.43- atoms to form corner-sharing CC4 tetrahedra. There is one shorter (1.54 Å) and three longer (1.56 Å) C–C bond length. In the second C+0.43- site, C+0.43- is bonded to one B3+ and three equivalent C+0.43- atoms to form corner-sharing CBC3 tetrahedra. All C–C bond lengths are 1.56 Å. In the third C+0.43- site, C+0.43- is bonded to four C+0.43- atoms to form CC4 tetrahedra that share corners with three equivalent BC4 tetrahedra and corners with nine CC4 tetrahedra. The C–C bond length is 1.51 Å. In the fourth C+0.43- site, C+0.43- is bonded to three equivalent B3+ and one C+0.43- atom to form distorted corner-sharing CB3C tetrahedra. In the fifth C+0.43- site, C+0.43- is bonded to four C+0.43- atoms to form CC4 tetrahedra that share corners with three equivalent BC4 tetrahedra and corners with nine CC4 tetrahedra. The C–C bond length is 1.55 Å. In the sixth C+0.43- site, C+0.43- is bonded to four C+0.43- atoms to form corner-sharing CC4 tetrahedra. All C–C bond lengths are 1.55 Å. In the seventh C+0.43- site, C+0.43- is bonded to four C+0.43- atoms to form corner-sharing CC4 tetrahedra.