Growth and organization of an organic molecular monolayer on TiO2: catechol on anatase (101).

Anatase TiO(2) is a widely used photocatalytic material, and catechol (1,2-benzendiol) is a model organic sensitizer for dye-sensitized solar cells. The growth and the organization of a catecholate monolayer on the anatase (101) surface were investigated with scanning tunneling microscopy and density functional theory calculations. Isolated molecules adsorb preferentially at steps.

Hydroxide ions at the water/anatase TiO2(101) interface: structure and electronic states from first principles molecular dynamics.

Hydroxide (OH(-)) ions at or near the interface between water and titanium dioxide (TiO(2)) have an important role in many surface photocatalytic reactions, possibly including the photo-oxidation of water. Using first principles molecular dynamics (FPMD) simulations on the time scale of 30-40 ps, we have investigated the structure and electronic properties of a solvated or adsorbed OH(-) at the interface between liquid water and a stoichiometric anatase TiO(2)(101) slab. We observed that a solvated hydroxide ion diffuses spontaneously from bulk water toward the anatase surface, a result consistent with the known point of zero charge for TiO(2) in water.

Energetics and diffusion of intrinsic surface and subsurface defects on anatase TiO2(101).

We report on density functional theory (DFT) calculations of the formation energies and diffusion pathways of oxygen vacancies and Ti interstitials at and near the (101) surface and in the bulk of the anatase polymorph of TiO(2). At the generalized gradient approximation level, both defects are found to be energetically more stable by approximately 0.5 eV or more at bulk and subsurface sites than on the surface.

Evidence for the predominance of subsurface defects on reduced anatase TiO2(101).

Scanning tunneling microscopy (STM) images taken on a freshly cleaved anatase TiO2(101) sample show an almost perfect surface with very few subsurface impurities and adsorbates. Surface oxygen vacancies are not typically present but can be induced by electron bombardment. In contrast, a reduced anatase (101) crystal shows isolated as well as ordered intrinsic subsurface defects in STM, consistent with density functional theory (DFT) calculations which predict that O vacancies (V_{O}'s) at subsurface and bulk sites are significantly more stable than on the surface.

Semiclassical dynamics of electron transfer at metal surfaces.

In this Letter, we demonstrate that nonadiabatic dynamics of molecular scattering from metal surfaces can be efficiently simulated by semiclassical Gaussian wave packet propagation on a local complex potential. The method relies on the wideband limit decoupling of the nuclear equations of motion on different electronic states. If the continuum diabatic potential surfaces are assumed to be parallel, the number of Gaussian wave packets spawned scales at most linearly with propagation time, allowing efficient propagation of nuclear dynamics.