First-principles Study On The Electronic Structures And Optical Properties Of WTe₂ Under Different Pressure

In order to study the pressure effect on the electronic structure and optical properties of WTe₂ by using density functional theory, firstly the full-potential local-orbital minimum-basis band-structure scheme is used to study the band structures of WTe₂ under the pressure of 1.22 GPa,2.4 GPa and 13.0 GPa. Then the full-potential linearized-augmented-plane-wave method is used to investigate the Fermi surfaces of WTe₂ under the pressure of 1.22 GPa,2.4 GPa and 13.0 GPa. Finally the projector augmented-wave method is used to study the optical properties of WTe₂ under the pressure of 1.22 GPa,2.4 GPa and 13.0 GPa. According to the band structures that we have calculated, we have found that WTe₂ has a semimetal-to-metal transition when the pressure increases from 2.4 GPa to 13.0 GPa. Otherwise, according to the Fermi surfaces that we have calculated, we have observed that a pair of hole-like Fermi surfaces along the Γ-X direction has disappeared when the pressure increases from 1.22 GPa to 2.4 GPa. Finally, according to the optical conductivity spectra, the reflectivity spectra and the electron energy loss spectra that we have calculated, we have observed that whether along x direction or along z direction, the reflectivity spectra coincides well with the corresponding electron energy loss spectra with respect to the peak positions. Furthermore, we have observed that whether along x direction or along z direction, the optical conductivity spectra of WTe₂ under the pressure of 2.4 GPa is roughly same as the optical conductivity spectra of WTe₂ under the pressure of 1.22 GPa. But the optical conductivity spectra of WTe₂ under the pressure of 13.0 GPa is different from the optical conductivity spectra of WTe₂ under the pressure of 2.4 GPa. Consequently we hold the view that when the pressure increases from 1.22 GPa to 2.4 GPa, although the pressure effect on the band structure of WTe₂ is very small, the pressure effect on the energy bands of WTe₂ near the Fermi level is relatively large. Then when the pressure continues to increase from 2.4 GPa to 13.0 GPa, the pressure has a large effect on the band structure of WTe₂. Correspondingly, the pressure has a large effect on the energy bands of WTe₂ near the Fermi level.