First-Principles-Based Deterministic Structure Search for Nitrogen Dioxide Adsorption on Titania Anatase Surfaces

Abstract

Structure searches using first-principles calculations were performed for the NO₂ adsorption on the TiO₂ anatase surfaces. The stable and metastable structures were enumerated for uni- and bimolecular adsorptions on the (101) and (001) anatase surfaces. In this study, exhaustive structure searches were performed using tDIRECT, which is based on the global optimization algorithm, DIRECT. This is in contrast to the structure searches based on chemical intuition in the literature, which exclusively targeted the unimolecular adsorptions. The number of enumerated structures was much larger in the bimolecular adsorption systems than in the unimolecular adsorption ones, indicating the importance of an exhaustive, rather than empirical, structure search for multiple adsorption systems. The adsorption energy of the obtained stable structure was −0.38 and −1.06 eV in the unimolecular adsorption, and −1.46 and −3.26 eV in the bimolecular adsorption on the (101) and (001) surfaces, respectively. Vibrational analyses showed that the eigenfrequencies and/or the IR-activity of the vibrational modes in the adsorption structures depended on the surface structures and the number of adsorbates.