First principles investigations of the influence of O-adsorption on the structural and electronic properties of TiC(111) surfaces with vacancies

We used ab initio calculations to systematically investigate the adsorption of atomic oxygen on non-stoichiometric polar TiC(111) and Ti xC y(111) with Ti/C vacancies surface simulating its potential tructions with laser radiation. Local atomic structures of O/Ti xC y(111) polar surfaces were studied in the selected models as well as their thermodynamic and electronic properties based on the density functional theory. The bond length and adsorption energy for various reconstructions of the O/Ti xC y(111) surface atomic structure were established. We also have examined the effects of oxygen adsorption upon the band and electron spectra of TiC(111) surface in its various reconstructions. We have established a correlation between the energy level of flat bands (- 5.1 eV and - 5.7 eV) responsible for the doublet of singular peaks corresponding to partial densities of oxygen 2p electrons and the energy of oxygen adsorption in non-stoichiometric O/TiC y(111) systems. Effective charges of the oxygen atom and the titanium and carbon atoms nearest to it were identified in the examined adsorption models. We have established charge transfer from titanium atom to oxygen and carbon atoms determined by the reconstruction of local atomic and electronic structures. Charge transfer correlates with the electronegativity values of titanium, carbon, and oxygen atoms, and chemisorption processes. Calculated values of structural parameters in the studied models of ultrathin O/TiC(111) and O/Ti xC y(111) films correlate well with experimental findings and other theoretical results. © 2016 Elsevier B.V.