First principles calculation on the newly superhard materials of W-B-C ternary system

W-B-C ternary systems were potential superhard materials because of the strong covalent bonds. Herein, a global crystal structure search was performed using the ab initio evolutionary algorithm implemented in the USPEX code, and 9 potential stable compounds were obtained. Then the structure, mechanical, electronic and lattice dynamic properties of these compounds were systematically calculated. The results show that all these compounds were thermodynamic, mechanical and dynamical stable by checking the formation enthalpy, elastic constants and phonon spectra, respectively. The Vickers hardness of R3m-W2B2C and R3m-W3B2C2 reached 36.75 GPa and 37.92 GPa, respectively, which was very close to the hardness of superhard materials (≥40 GPa), and the Vickers hardness of Rm-W3B2C2 and Cm- W4B2C3 also reached 32.26 GPa and 31.71 GPa. Then the electronic and crystal structure of R3m-W2B2C, R3m-W3B2C2, R3‾m-W3B2C2 and Cm-W4B2C3 were analysed, the results show that all these compounds have significant electron localization phenomenon around B and C atoms, this strong interaction between transition metal W and B, C atoms and the layered structure with robust W-B bonds were the just reason why these compounds were so hard. •9 potential superhard materials were uncovered in W-B-C ternary systems.•The Vickers hardness of R3m-W2B2C and R3m-W3B2C2 reached 36.75 GPa and 37.92 GPa, respectively.•The hardness was obviously increased due to the strong covalent bond between the B and C atoms.