Comparative study of the structural, mechanical, electronic, optical and thermodynamic properties of superconducting disilicide YT2Si2 (T=Co, Ni, Ru, Rh, Pd, Ir) by DFT simulation

Abstract

DFT simulation-based ab-initio approach has been executed for examining the relative physical properties of superconducting disilicide materials YT2Si2 (T = Co, Ni, Ru, Rh, Pd, Ir). This is the first comparative theoretical investigation of these materials, which is done through Cambridge Serial Total Energy Package module. Extremely good relation has been observed between the synthesized and calculated structural parameters of all the superconductors. Mechanical structural stability of all the phases has been confirmed from the investigated elastic stiffness parameter. The phonon dispersion curve indicates that the YT2Si2 compounds with T = Co, Ni, Ru, and Ir are dynamically stable, but those with T = Rh and Pd are dynamically unstable. The investigated elastic moduli show good agreement with previously calculated data where available. Also, the fundamental polycrystalline features such as bulk modulus, shear modulus, Young's modulus, Pugh's and Poison's ratios, ductile/brittle nature and hardness of superconducting YT2Si2 (T = Co, Ni, Ru, Rh, Pd, Ir) have been examined. Ductile nature of YRh2Si2, YPd2Si2 and brittle nature of YCo2Si2, YNi2Si2, and YIr2Si2 have been observed from analyzing of polycrystalline elastic parameters where YRu2Si2 lies on the border line of ductile/brittle nature. The high bulk modulus, Young's modulus, and hardness of YIr2Si2 ensured that this phase has high ability to resist volume and plastic deformation and suitable in industrial applications. On the other hand, the small Young's modulus of YPd2Si2 ensured its application as a thermal barrier coating (TBC) material. Metallic nature of YT2Si2 (T = Co, Ni, Ru, Rh, Pd, Ir) has been confirmed from the band structure and DOS calculations. Mulliken atomic populations and charge density map reveal the existing of covalent and ionic bond inYT2Si2 (T = Co, Ni, Ru, Rh, Pd, Ir). Different optical features like dielectric function, refractive index, photo conductivity, reflectivity, absorption and loss function of YT2Si2 (T = Co, Ni, Ru, Rh, Pd, Ir) have been executed through CASTEP code directly. The elevated reflectivity in the UV energy site of these phases ensured their application as good solar reflector in this energy site. Furthermore, the thermodynamic properties of superconducting YT2Si2 (T = Co, Ni, Ru, Rh, Pd, Ir) have been determined from the elastic stiffness constants. The high conductivity of YCo2Si2 is ensured from its high Debye and melting temperature. The minimum thermal conductivity of YPd2Si2 ensured that it is suitable to use as a thermal barrier coating (TBC) material.