Atomic and electronic structure ofWSe2fromab initiotheory: Bulk crystal and thin film systems

Abstract

We report on ab initio bulk and surface atomic and electronic structure calculations of ${\mathrm{WSe}}_{2}.$ The calculations are based on the local-density approximation employing nonlocal, normconserving pseudopotentials together with Gaussian orbital basis sets. We have carried out a fairly general case study including analyses of the effects of basis set, k integration, structure parameters, and relativistic corrections on the band structure and the atomic properties. We find that the energy of particular band-edge states is extremely sensitive with respect to the lattice parameters and to spin-orbit coupling. Our results for the bulk atomic and electronic structure resolve recent controversies in these quantities, as discussed in the literature, and shed light on their origins. In particular, it had been suggested that surface effects might be the cause of the deviations. To resolve this issue, we have studied surface atomic and electronic properties for a number of ${\mathrm{WSe}}_{2}$ thin films. Our results allow us to quantitatively interpret experimental results from angle-resolved photoemission spectroscopy and to predict the influence of the film thickness on electronic properties.