First-principles study of the effect of pressure on the physical properties of PbC

Silicon carbide has been used as a cutting material and as a semiconductor in lighting and power electronics. Results from some studies, carried out on IV-IV group carbides like GeC and SnC, allow to identify potential technological applications of these carbides in extreme environments, opening the possibility to find new carbides for similar applications. For this work, the PbC was studied under hydrostatic pressure in the framework of the Density Functional Theory, obtaining relevant information on its structural, electronic, mechanical, vibrational, thermodynamical, and optical properties. The optimized lattice parameter and volume, and electronic bands structures type agree with the available theoretical data at zero GPa. The calculated enthalpy values show a phase transition, from the B3 structure (CsCl-type) to the B1 structure (rocksalt or NaCl-type), at 23.5 GPa. The PbC is energetically, mechanically, and dynamically stable for all the pressure values in the studied range; it is a metallic, anisotropic, and brittle material with paramagnetic ionic-covalent bonds and good hardness (the highest mechanical resistance was found above T = 370 K). As the pressure increases, it was noted: (i) the increase of the electronic cloud around the C and Pb atoms, (ii) the DOS spread, (iii) the change to be a ductile material with a tendency to the metallic bonds and (iv) an increase of the hardness and the Young modulus, due to C 2p and Pb 6p-orbitals. Our results show that the PbC is a promising material for applications in the development of optical and optoelectronic devices, and to be used as a protective coating against the low frequencies in the UV and infrared and visible regions.