Ab initio study of strain and electric field dependent variation in electronic and thermoelectric properties of PdS2

Abstract

Ab initio calculations based on plane wave methods show that the band gap of PdS2 is strongly dependent upon the thickness of layers including van der Waals (vdW) interactions. The valence band maximum (VBM) is sensitive to the out-of-plane, and the conduction band minimum (CBM) to the in-plane lattice constants. The out of plane bonding is enhanced by the vdW force, which in turn affects the in-plane bonding. On application of biaxial compressive and tensile strain, the band gap decreases from 1.03 eV to 0.27 eV & 0.14 eV and 0.04 eV & 0.32 eV in case of bilayers with different stackings (AA & AB) respectively. The band gap is found to decrease from 1.03 eV to 0.0 eV (0.03 eV) and 0.0 eV (0.05 eV) on applying an electric field in the z direction on AA (AB) bilayers of PdS2. The effects of strain on the thermoelectric properties of PdS2 monolayer and bilayer were also studied. The electrical conductivity increases with the increase in tensile strain while it decreases with compressive strain in bilayers. As expected for thermoelectric application, the trend in the variation of the Seebeck coefficient is of opposite nature. The present work demonstrates the flexibility available for modulating the electronic and thermoelectric properties of this material for a variety of different applications.