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Theory of oxide surfaces, interfaces, and supported clusters

Cristiana Di Valentin, Livia Giordano, Sergio Tosoni, Gianfranco Pacchioni

The understanding of the structure-properties relationship is of fundamental importance for the design of new materials. In our group various models are employed to study the electronic structure of inorganic and ceramic materials in combination with highly accurate quantum-mechanical techniques.

Particularly important is the role of theory in the study of local sites or phenomena like atomic and molecular chemisorption, point defects, impurities in solids, active sites or functional groups on surfaces, ultrathin films, supported clusters, light-matter interactions, and for the interpretation of various spectroscopies, IR and Raman, X-ray absorption and photoemission, EPR and NMR, optical transitions, STM etc.

Thin oxide films
Ultrathin oxide films grown on metal supports represent a new class of materials with unprecedented properties. Our activity is directed towards the determination of the electronic and structural properties of these systems, in particular work function changes, presence of nanoholes or regular arrays of adsorption sites, reactive sites, etc.

Supported clusters
Metal nanoclusters as models of supported catalysts. We study the interaction and stabilization of the metal clusters at specific sites of the support like oxygen vacancies and other defects. We investigate the possible electronic modification of metal clusters on ultrathin insulating films due to electron tunneling phenomena from the metal support (charging, change in shape and reactivity, etc.). We also study the reactivity of supported clusters in elementary steps of catalytic reactions.

Gruppo Pacchioni

Oxide surfaces
Structure and properties of oxide surfaces and of their interaction with adsorbed molecules. Materials of technological interest in catalysis include very ionic solids like MgO and CaO, more covalent oxides like SiO2, and intermediate cases like TiO2 and Al2O3. The group is specialized in the study of chemisorption and reactivity, especially at surface defects, and in the characterization of surface morphology.

Defects and dopants in oxides

Nature of point defects in oxide materials for photocatalysis, photoelectrochemistry, microelectronics, fiber optics, , etc. in particular amorphous and crystalline TiO2, ZnO, WO3, SiO2, alkaline earth oxides. The activity is directed toward the determination of stability, structure, and spectral properties of intrinsic and extrinsic point defects (vacancies, metal and non-metal dopants, codopants, hydroxyl groups, trapped electrons, etc.) and their interplay through charge transfer processes. Particular attention is devoted to the study of optical absorption for activation in the visible region and of electron spin resonance spectra for identification of paramagnetic centres.