Stabilization of charge-density waves in 1T-TaX2(X=S,Se,Te):: First-principles total energy calculations -: art. no. 195101

The quasi-two-dimensional transition-metal dichalcogenide compounds 1T-TaX2(X=S,Se,Te) at low temperature form charge-density waves (CDW), manifested in periodic lattice distortions. In order to investigate the effect of the CDW on the Fermi surface (FS) of these compounds, the FS cross sections in various planes are calculated and the nesting vectors are determined. The CDW is treated as single q commensurate frozen phonons of wave vectors around the candidate FS nesting vectors. The lattice distortions caused by the CDW are then reproduced using the total energy and force calculations performed within these supercells using the full potential linearized augumented plane-wave method. It was found that these compounds are unstable towards the CDW state. Our FS calculations for the CDW distorted state confirm the presence of gaping in the FS indicating that electron-phonon coupling plays an important role in the stabilization of the CDW in the compounds under investigation.