Theoretical study of the layer number and strain effects on the structural and electronic properties of Platinum diselenide (PtSe2) material

In recent years, two-dimensional materials have attracted great interest due to their exceptional properties, which differ significantly from bulk materials. Platinum diselenide (PtSe₂) material has shown various electronic features when going from bulk to monolayer (ML). In this work, density functional theory (DFT) plus van der Waals (vdW) corrections have been considered to study the structural and electronic properties of different PtSe₂ systems, namely ML, bilayer (BL), trilayer (TL), ourlayer (FL), and bulk. In particular, various vdW corrections, have been tested to describe the inter-layer interaction of PtSe₂ material. The accuracy of these corrections is evaluated according to the comparison with the available experimental results. Our results show that while vdW corrections have no significant effect on the electronic structure of bulk PtSe₂, they significantly alter that of PtSe₂ BL, TL and FL materials. In fact, in the case of these three latter systems, a correlation between the inter-layer distance and the bandgap feature was obtained. Indeed, the bandgap of PtSe₂ increases with the increase of the inter-layer distance. According to our calculations, PtSe₂ ML and BL-PtSe₂ are indirect gap semiconductors with gap energies of approximately 1.34 and 0.21eV, respectively. Furthermore, the control of the inter-layer distance via vertical strain is considered. The electronic properties of bulk can be obtained for PtSe₂ BL under -17 % vertical strain. Our work shows a deep understanding of the correlation between the structural and electronic properties, and thus a possibility to tune the band gap by strain means.