inverted optical band gaps tagged posts

Various configurations of oxygen adsorption with corresponding energies. (a) Sulphur, molybdenum, and oxygen are represented by yellow, blue, and red spheres, respectively. The sulphur vacancy site is represented by the cross. (b) Nudged elastic band calculation of the energy barrier for migration of an oxygen molecule towards a sulphur vacancy and respective trapping. The energy barrier, measured from the starting point, is 56 meV. The calculation was performed in the spin-averaged state. (c) Calculated ionization levels for relevant defects (all energies are in eV). VBM and CBM refer to the valence band maximum and conduction band minima, respectively. (d) Representation of the charge density of the trapped electrons at sulfur vacancies.