Humaira Takia^1,, Md. Afjalur Rahman², Rahman Moshiur³, M.M. Rahaman⁴, Khokon Hossen¹

In the impending lesson, we explore the substantive features of PbX (S, Se and Te) such as structural, elastic, electronic and optical properties using first principle calculations based on the density functional theory. Generalized gradient approximation (GGA-PBEsol) is used as an exchange-correlation functional for the structural properties of the different crystal phases. For all phases, the optimized lattice parameters display a strong covenant with the available experimental data. The three independent elastic constants (C₁₁, C₁₂, and C₄₄) for all three compounds are positive and fulfill the Born stability criteria, which ensures that all phases possess the mechanical stability in nature. The most significant elastic properties like Bulk modulus (B), shear modulus (G), Young’s modulus (Y), Poisson’s ratio (ν) and elastic anisotropy (A) of the cubic-type structure of PbX (X=S, Se and Te) are estimated and observed under ambient pressure. The Cauchy pressure and Pugh’s ratio reveals that all compounds exhibit brittle nature and the band structure analysis ensures the semi-metallic character with a narrow band gap of all these phases. The obtained values of band gap are 0.23 for PbS, 0.15 eV for PbSe, and 0.58 eV for PbTe respectively. At last, it has been obtained and smeared the several optical properties such as absorption, conductivity, reflectivity, loss function, dielectric function and refractive index at the polarization vector [100] of PbX (X=S,Se and Te) in details. The higher reflectivity spectra of these compounds in the Infrared and ultraviolet regions demonstrate promise as excellent shielding materials for avoiding solar heating.

Pb-based compounds, first principle study, density functional theory, generalized gradient approximation, pseudo-potential, geometry optimization