Prediction of a sandwichlike conducting superhard boron carbide: First-principles calculations

Our first principles calculations predict a tetragonal BC3 (t-BC3) phase originating from the cubic diamond structure. The t-BC3 structure is formed by alternately stacking sequence of metallic CBC and insulating CCC blocks, exhibiting a sandwichlike metal and/or insulator layered structure with the anisotropic conductivity on the basal planes formed by the metallic CBC blocks. Its stability has been confirmed by our calculations of the total energy, elastic constants, and phonon frequencies. A low critical pressure of similar to 4 GPa for a synthesis of the t-BC3 from the graphitelike BC3 (g-BC3) is expected.