Cristiana Di Valentin

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The removal of lattice O atoms, as well as the addition of interstitial H atoms, in TiO(2) is known to cause the reduction in the material and the formation of "Ti(3+)" ions. By means of electronic structure calculations we have studied the nature of such oxygen vacancy and hydrogen impurity states in the bulk of the anatase polymorph of TiO(2). The spin(More)
Nitrogen-doped titanium dioxide (N-TiO2), a photocatalytic material active in visible light, has been investigated by a combined experimental and theoretical approach. The material contains single-atom nitrogen impurities that form either diamagnetic (Nb-) or paramagnetic (Nb*) bulk centers. Both types of Nb centers give rise to localized states in the band(More)
Electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations are combined for the first time in an effort to characterize the paramagnetic species present in N-doped anatase TiO2 powders obtained by sol-gel synthesis. The experimental hyperfine coupling constants are well reproduced by two(More)
It has been experimentally observed that a bridging oxygen vacancy on the rutile TiO2(110) surface introduces localized Ti3+ 3d1 states about 1 eV below the conduction band which are not removed upon dissociation of a water molecule and formation of a pair of hydroxyl groups. Density functional calculations based on pure exchange-correlation functionals(More)
A hybrid density functional study based on a periodic approach with localized atomic orbital basis functions has been performed in order to compute the optical and thermodynamic transition levels between different charge states of defect impurities in bulk ZnO. The theoretical approach presented allows the accurate computation of transition levels starting(More)
The "catalysis under cover" involves chemical processes which take place in the confined zone between a 2D material, such as graphene, h-BN, or MoS2, and the surface of an underlying support, such as a metal or a semiconducting oxide. The hybrid interface between graphene and anatase TiO2 is extremely important for photocatalytic and catalytic applications(More)
This paper deals with the microscopic mechanism of nanolithography of self-assembled monolayers (SAM) of alkanethiol molecules on Au(111) induced by the exposure of the film to a beam of "cold" Cs atoms. Density functional theory calculations have been carried out to elucidate the mechanism of interaction of the Cs atoms with the SAM. We found that the film(More)
We investigate the long-standing problem of hole localization at the Al impurity in quartz SiO2, using a relatively recent DFT hybrid-functional method in which the exchange fraction is obtained ab initio, based on an analogy with the static many-body COHSEX approximation to the electron self-energy. As the amount of the admixed exact exchange in hybrid(More)
We investigate the behavior of oxygen vacancies in three different metal-oxide semiconductors (rutile and anatase TiO2, monoclinic WO3, and tetragonal ZrO2) using a recently proposed hybrid density-functional method in which the fraction of exact exchange is material-dependent but obtained ab initio in a self-consistent scheme. In particular, we calculate(More)
An important step in oxide photochemistry, the loading of electrons into shallow trap states, was studied using infrared (IR) spectroscopy on both, rutile TiO2 powders and single-crystal, r-TiO2(110) oriented samples. After UV-irradiation or n-doping by exposure to H-atoms broad IR absorption lines are observed for the powders at around 940 cm(-1). For the(More)