First-principles prediction of outstanding mechanical and thermodynamic properties of YX2Si2 (X = Pd and Rh) superconductors

Abstract

Superconductivity is a macroscopic quantum phenomenon with unprecedented applications in high-efficient power transmission, electric motors, generators, transportation, particle accelerators, and computing. Although the superconducting capabilities of YX2Si2 (X = Pd, and Rh) compounds have been experimentally realized, the physical aspects of these two superconductors are yet to be understood. Herein, employing first-principle-based Density Functional Theory (DFT) calculations, we realized the excellent mechanical strength of the YRh2Si2 compound. Firstly, the estimated X-ray diffraction, as well as unit cell parameters of both superconductors, show excellent conformity with prior experimental data. Also, mechanical parameters which are most fundamental, including bulk modulus, shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, ductility, and Vickers hardness factors of both superconductors have been evaluated. Despite the brittle nature, YRh2Si2 shows excellent mechanical strength compared to that of YPd2Si2. Besides, the assessment of the density of states, Mulliken atomic populations, and charge density map reveals a complex chemical bonding in both superconductors including ionic, covalent, and metallic features. Furthermore, charge density data suggest that Si-Si, Si-Pd, and Si-Rh bonds are indeed covalent while Pd-Pd and Rh-Rh demonstrate metallic features. Afterward, different optical parameters such as dielectric functions, reflectivity, absorption coefficient, refractive index, photoconductivity, and loss function of both superconductors have been anticipated. Notably, it has been unveiled that both superconductors show excellent absorption and photoconductivity in the ultraviolet region of the electromagnetic spectrum. Additionally, sound velocity, Debye temperature, melting point, and minimum thermal conductivity of both superconductors have been estimated from DFT computation. Interestingly, most of the thermodynamic parameters of YRh2Si2 are notably higher compared to those of the YPd2Si2 compound. Remarkably, the DFT results suggest that YRh2Si2 exhibits excellent mechanical as well as thermodynamic properties compared to other reported superconductors of identical classes.