Model studies of the structure and optical properties of the TiO2(110) surface with an adsorbed Ag atom

ABSTRACT

The present studies of the atomic Ag adsorbate on the substrate TiO₂(110) explore the importance of dispersion (or van der Waals) energies for determining the structure of the adsorbed Ag atom, using density functional theory (DFT) supplemented by a dispersion energy treatment, within the PBE-D3 treatment. It is also of interest to explore electronic excitation by light absorption. Electronic density of states (EDOS) are obtained without and with Ag adsorbed on the TiO₂(110), to find the extent of change on the density of valence, conduction and intraband states. This is done using the hybrid HSE06 functional, which is known to provide good values for the energy band gap of the substrate. A computationally efficient PBE?+?BG procedure for these structures, which corrects the PBE band gap, is implemented to generate accurate EDOSs and light absorption intensities versus photon energies. This is followed by a reduced density matrix treatment of the dissipative dynamics of light absorption, generating state-to-state oscillator strengths and photoabsorbances for the pure and nanostructured TiO₂(110) surfaces. Adsorption of Ag leads to a noticeable increase in light absorption at visible wavelengths, and very large increases in the UV region of the spectrum.