A revisit to the electronic and elastic properties of B4C: A DFT study

Globally known as one of the hardest covalent material, the application of boron carbide (B4C) on many technology fronts are hindered by high brittleness and uncertainties on its structural and electronic mechanisms. Here, we investigated seven polytypes of B4C and supercell structure containing two polytypes based on SCAN functional of density functional theory (DFT) technique. All of calculated parameters have better accuracy compared to previous studies. From electronic and elastic perspectives, we determine that supercell structure formed by combining B11Cp-CBC and B11Ce-CCB polytypes is the most realistic out of all considered polytypes. The insulating behavior due to the mid-gap states is calculated to be 1.98 eV. The gap can be increased while retaining its characteristics by increasing the ratio of B11Cp-CBC polytype, emulating a disordered nature of B4C system. The suggested structure is second hardest system at 34 GPa, slightly lower than the major polytype of B11Cp-CBC.