Carbon-rich icosahedral boron carbide designed from first principles

The carbon-rich boron-carbide (B11C)C-C has been designed from first principles within the density functional theory. With respect to the most common boron carbide at 20% carbon concentration B4C, the structural modification consists in removing boron atoms from the chains linking (B11C) icosahedra. With C-C instead of C-B-C chains, the formation of vacancies is shown to be hindered, leading to enhanced mechanical strength with respect to B4C. The phonon frequencies and elastic constants turn out to prove the stability of the carbon-rich phase, and important fingerprints for its characterization have been identified.