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.