First-principles calculations to investigate strain effects on structural, electronic, elastic and transport properties of Cs2PdBr6

Abstract

In this work, we have investigated the structural, electronic, elastic and transport features of the Cesium Hexabromopalladate (IV) Cs2PdBr6 using density functional theory (DFT) and Boltzmann transport theory implemented in Quantum Espresso and BoltzTraP simulation software. The findings suggest that the unconstrained Cs2PdBr6 is a direct semiconductor (Eg = 0.75 eV) and that the electronic band gap can be tuned by applying an external compressive or tensile strain. The structural properties of the Cs2PdBr6 compound have shown that the pressure and the uniaxial stretch produce a subtle distortion in the primitive unit cell. In the elastic properties, we focused on elastic constants, Pugh factor, Poisson ratio, and Young modulus. The examination of the elastic stabilities of Cs2PdBr6 shows that is mechanically stable because the elastic coefficients satisfy the Born's mechanical stability condition. Furthermore, the transport properties are simulated through the generalized gradient approximation presented by Perdew–Burke–Ernzerhof (GGA-PBE). It is observed that the Seebeck coefficient is very responsive to strain and that the studied compound has undergone a transformation from n-type to p-type conducting behavior. More interestingly, the figure of merit can be enhanced or attenuated under strains and the highest value (ZT ≈ 1) is found at room temperature at −6%. Our results show that the Cs2PdBr6 compound is an excellent candidate for thermoelectric applications.