A first-principles study of the electronic, mechanical, vibrational, and optical properties of the zirconium carbide under high pressure

Abstract

Zirconium carbide is a compound widely used in cutting tools, nuclear reactors, field emitter arrays and solar energy receivers; additionally, combined with other materials, it can be used in rocket technology and the aerospace industry. For this work was studied the effect of the high hydrostatic pressure on the electronic, mechanical, vibrational, and optical properties of the ZrC, from first principles calculations based on the Density Functional Theory. The calculated enthalpy and cohesive energy data show a B1 (NaCl) to B2 (CsCl) phase transition at 297 GPa. Besides, results for the calculated equilibrium lattice parameters, bands structure, electron and phonon densities of states, elastic moduli constants, entropy, enthalpy, Gibbs free energy, heat capacity, reflectivity, loss function, conductivity, and dielectric function are consistent with the available experimental and theoretical data. The B1 phase is dynamically stable; in contrast, the B2 phase is not stable. Furthermore, when pressure is applied, the C 2p-orbitals around the Fermi energy contribute significantly to the conduction band, turning ductile the material, with a mixture of metallic and ionic-covalent bonds. On the other hand, ZrC exhibits its highest mechanical resistance, and maximum thermal absorption, above 356° K and 638° K, respectively; but these switch to higher temperatures as pressure is applied. Finally, this compound is a good coating material and a photon detector at low frequencies in the UV region, but also at the visible and infrared regions; although, increasing the pressure, the values of the optical properties increase. The parameters values’ increase of the studied properties, as the pressure increases, indicates that zirconium carbide at high pressures can be used in a greater range of applications more efficiently.

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

“…The free energy dependence of the structure is completely contained in E a i { }if anharmonic effects are neglected, consequently the structure is independent of T. However, if the phonon frequencies depend on the structural parameters (quasi-harmonic approximation), the equilibrium structure could be obtained at any temperature T as described in [52]. The vibrational entropy (S), and the lattice contribution to the heat capacity (C v ) can be calculated as [53]; for the case of the Cv can be obtained as a function of the empirical Debye temperature (Θ D ) [54].…”

Theoretical study on the structural, electronic, mechanical, vibrational, thermodynamical, and optical properties of the two-dimensional PbC nanomaterials

“…The equilibrium structure of a crystal without pressure can be found by minimizing the Helmholtz free energy (F). Considering a perfectly harmonic crystal, the internal energy is the sum of the ground state total energy and the vibrational free energy [52]; moreover, considering the dependence of the phonon frequencies on the structural parameters, the equilibrium structure (at any T ) can be obtained as described in [53]. Vibrational parameters such as the entropy (S) and the heat capacity (C v ) can be calculated in [54], and the Debye q D in [55].…”