A detailed computational study to investigate the influence of metals (Bi, Sn, Tl) substitution on phase transition, electronic band structure and their implications on optical, elastic, anisotropic and mechanical properties of PbHfO3

By using first-principles calculations in line with density functional theory, the structural, electronic, optical, elastic and mechanical properties of pure and substituted PbHfO3 have been investigated. Here the substituated elements are Bi, Sn and Tl. To express the effect of substitution, all computations are determined by a generalized gradient approximation and an ultra-soft pseudopotential. In the current research, Bi, Sn, and Tl are substituted at the Pb-site which is preferable to the Hf-site due to the stability of cubic perovskites. According to the structural properties, cubic to pseudo-cubic transition is obvious. Moreover, the decline in band gap is noticed, when specific concentration of impurities (Bi, Sn) atoms are substituated. However, substitution of Tl increases the gap between conduction/valence bands. It is not just the change in band gap that increases or decreases, the nature is also shifted from indirect to direct. Moreover, this behaviour is explained by the different density of states. Since then, a significant alteration in band gap is mainly due to the p-states. As a result, our material is a favourable choice for optoelectronic devices. The changes in electronic characteristics also influence the optical properties including the complex dielectric functions, absorption, reflectivity, loss function, and refractive index. We also explored the elastic constants (C-ij), stability criteria, and mechanical attributes like Bulk modulus (B), Young's modulus (Y), shear modulus (G), Poisson's ratio (upsilon) and anisotropic factor (A). Furthermore, we came to the conclusion that our material is elastically stable, ductile and stiff.