Computational Modeling of Crystal Structures, Mechanical Properties, and Vibrational Spectra of Superhard B-C and B-N systems *

Superhard materials with a Vickers hardness larger than ~40 GPa have a wide range of industrial applications such as cutting tools and protective coatings. Superhard boron-carbon (B-C) and boron-nitride (B-N) composites are especially important because of their superior high-temperature performance as compared to diamond and their low reactivity with ferrous metals. Here we employ the powerful evolutionary algorithm as implemented efficiently in the USPEX software to predict the crystal structures of superhard B-C and B-N composites. The mechanical properties, electronic structures, phonon and Raman spectra of these predicted structures are computed accordingly also from first principles using density functional theory. Comparison of our calculations and available experimental data will also be discussed.