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Accurate description of thermodynamic, structural, and electronic properties for bulk and surfaces of ceria (CeO2) necessitates the inclusion of the Hubbard parameter (U) in the density functional theory (DFT) calculations to precisely account for the strongly correlated 4f electrons. Such treatment is a daunting task when attempting to draw a potential energy surface for CeO2-catalyzed reaction. This is due to the inconsistent change in thermo-kinetics parameters of the reaction in reference to the variation in the U values. As an illustrative example, we investigate herein the discrepancy in activation and reaction energies for steps underlying the partial and full hydrogenation of acetylene over the Ce[O.sub.2](111) surface. Overall, we find that both activation and reaction energies positively correlate with the increase in the U value. In addition to benchmarking against more accurate theoretical methodologies, we suggest that U values are better optimized against kinetics modelling of experimentally observed profiles of products from the catalytic-assisted system of reactions. Key words: ceria, DFT + U, reaction barriers, hydrogenation of acetylene, catalysts, transition state, Hubbard parameter (U). Une description precise des proprietes thermodynamiques, structurelles et electroniques de volume et de surface de l'oxyde de cerium (CeO2) requiert l'inclusion du parametre de Hubbard (U) dans le cadre d'un calcul en theorie de la fonctionnelle de densite (TFD), afin de tenir compte de facon precise des electrons 4f fortement correles. Un tel calcul est un defi important lorsqu'on tente d'obtenir la surface d'energie potentielle pour une reaction catalysee par Ce[O.sub.2]. Ceci est du au changement incoherent dans les parametres de reaction face a la variation de la valeur de U. Comme exemple illustratif, nous examinons ici le desaccord entre les energies d'activation et de reaction dans les etapes sous-jacentes a l'hydrogenation partielle et complete de l'acetylene sur une surface (111) de Ce[O.sub.2]. En resume, nous trouvons que ces deux energies sont correlees positivement avec l'augmentation de U. De plus, comme reference face a des methodes theoriques plus precises, nous suggerons d'optimiser les valeurs de U selon la modelisation cinetique des profils experimentaux de produits de reactions assistees par catalyse. [Traduit par la Redaction] Mots-cles : oxyde de cerium, hydrogenation, barriere de reaction, TFD, catalyse., 1. Introduction Cerium oxide (CeO2, ceria) and materials based on it are essential in many strategic catalytic industrial applications [1-3]. As oxygen-storage ingredients [4], they are utilized in three-way catalysts [...]

Abstract Ce/Ti mixed metal oxide thin films have well known optoelectrical properties amongst several other physio-chemical properties. Changes in the structural and mechanical properties of magnetron sputtered Ce/Ti oxide thin films on Si (100) wafers with different Ce:Ti ratios are investigated experimentally and by modelling. X-ray Photoemission Spectroscopy (XPS) and X-ray diffraction (XRD) confirm the primary phases as trigonal Ce 2 O 3 and rutile form of TiO 2 with SiO 2 present in all prepared materials. FESEM imaging delivers information based on the variation of grain size, the mixed Ce/Ti oxides providing much smaller grain sizes in the thin film/substrate composite. Nanoindentation analysis concludes that the pure cerium oxide film has the highest hardness value (20.1 GPa), while the addition of excess titanium oxide decreases the hardness of the film coatings. High temperature in-situ XRD (up to 1000 °C) results indicate high thermal phase stability for all materials studied. The film with Ce:Ti = 68%:32% has a new additional minor oxide phase above 800 °C. Contact angle experiments suggest that the chemical composition of the surface is insignificant affecting the water contact angle. Results show a narrow band of 87.7–95.7° contact angle. The finite element modelling (FEM) modelling of Ce/Ti thin film coatings based on Si(100); Si(110); silica and steel substrates shows a variation in stress concentration. [ABSTRACT FROM AUTHOR]