Prediction of stabilities phase and elastic properties of Palladium Carbide

First-principles calculations are carried out to investigate the stabilities and mechanical properties of ideal stoichiometric palladium monocarbide (PdC) in the five different phases, the rocksalt (B1), the zinc blende (B3), cesium chloride (B2), the tungsten carbide (WC), and the nickel arsenide (B8). Our calculations confirm only for the two hexagonal phases namely B8-PdC and WC-PdC, the PdC is mechanically stable and in the nickel arsenide (B8) structure the PdC is found most energetically favourable phase than the other phases with a large bulk modulus (B = 329 GPa, B′ = 4.006) and very high shear modulus (501.3 GPa), while in three cubic phases (B1, B2 and B3) is mechanically unstable. In the two hexagonal phases, the incompressibility along the c-axis is demonstrated very high. The different ground state properties such as the equilibrium lattice constant, electronic structure, elastic constants, the bulk modulus and its pressure derivate of PdC in these phases are systematically predicted by calculations from first-principles. The elastic constants and their pressure dependence are calculated in both phases mechanically stables (B8 and WC): we found a linear dependence of elastic stiffness on the pressure. From the total and partial (DOS), we found that PdC in both hexagonal phases (B8 and WC) is metallic. In addition, we estimated the Debye temperature of this compound from the average sound velocity in the two hexagonal phases mechanically stables (B8 and WC). We also present results of the hardness of PdC: we found that the PdC is superhard material in B8 phase and is hard material in WC phase.