Electronic structure and Fermi-surface-related instabilities in1T−TaS2and1T−TaSe2

Abstract

The electronic-energy-band structure and full-Brillouin-zone Fermi surfaces of the layered dichalcogenides, $1T-\mathrm{T}\mathrm{a}{\mathrm{S}}_2$ and $1T-\mathrm{T}\mathrm{a}{\mathrm{Se}}_2$, have been calculated using the Korringa-Kohn-Rostoker method in the muffin-tin approximation. We find that the Fermi surfaces for both systems away from symmetry points and lines have cross sections which are approximately constant along the $z$ direction. Strong nesting features of the Fermi surface are found for a spanning vector parallel to the $\Gamma M$ direction in reciprocal space with values in good agreement with the charge-density-wave results found by Wilson, Di Salvo, and Mahajan for these compounds.