A Hybrid Density Functional Theory Investigation of the $$({\text {CeO}}_2)_{6}$$ ( CeO 2 ) 6 Clusters in the Cati
- PDF / 1,555,551 Bytes
- 8 Pages / 595.276 x 790.866 pts Page_size
- 72 Downloads / 159 Views
(0123456789().,-volV)(0123456789().,-volV)
ORIGINAL PAPER
A Hybrid Density Functional Theory Investigation of the (CeO2 Þ6 Clusters in the Cationic, Neutral, and Anionic States Mailde S. Ozo´rio1 • Augusto C. H. Da Silva1 • Juarez L. F. Da Silva1 Received: 4 June 2019 Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract We report a quantum-chemistry investigation of the cationic, neutral, and anionic ðCeO2 Þ6 clusters to obtain an atom-level understanding of the effects induced by the release or addition of a single electron on the physical and chemical properties of small oxide clusters. Our ab initio calculations are based on density functional theory (DFT) within the hybrid Heyd– Scuseria–Ernzerhof (HSE06) and semilocal Perdew–Burke–Ernzerhof (PBE) functional. Compared with PBE, the HSE06 functional changes the relative stability of the neutral ðCeO2 Þ6 isomers, in particular, for structures with small total energy differences, e.g., about 100 meV/fu, which can be explained by the enhancement of the exchange interactions. The addition of an electron to the ðCeO2 Þ6 clusters change the oxidation state of a single Ce atom from ? IV to ? III, which drives a local distortion and the formation of a small polaron near to the CeIII cation. In contrast, the release of an electron induces the formation of a localized hole on one of the O atoms combined with local structural distortions. For the anionic and cationic clusters in the putative global minimum configurations, we found a strain energy induced by the distortion of 1.00 and 1.31 eV, respectively. Keywords Cerium oxide Clusters Density functional theory Abbreviations DFT density functional theory PBE Perdew–Burke–Ernzerhof HSE06 Heyd–Scuseria–Ernzerhof FHI-aims Fritz–Haber Institute ab initio molecular simulations
Electronic supplementary material The online version of this article ( https://doi.org/10.1007/s10876-019-01728-z ) contains supplementary material, which is available to authorized users. & Juarez L. F. Da Silva [email protected] 1
Sa˜o Carlos Institute of Chemistry, University of Sa˜o Paulo, PO Box 780, Sa˜o Carlos, SP 13560-970, Brazil
Introduction Cerium oxides (CeO2x , 0 x 12) have a special role in catalysis as support for transition-metal (TM) particles for water-gas-shift reactions [1, 2], three-way catalysts, [3, 4] ethanol dehydrogenation [5]. Furthermore, CeO2x clusters have been employed as catalysts for the oxidation of small molecules, e.g., SO2 [6], C2 H2 [7], etc. [8, 9]. The figure of merits of CeO2x is related to the high thermodynamic stability and to the oxygen storage/release capacity [2, 4, 10], which is connected to the behavior of the Ce fstates. For example, the Ce f-states can change their behavior from delocalized (CeþIV ) to localized (CeþIII ) by tuning the magnitude of the charge transfer among the Ce and O atoms using the presence of oxygen vacancies, [11, 12] CeO2x composition [13], TM atoms supported on CeO2 ð111Þ [14, 15]. Thus, a wide range of experimental [1, 2, 8, 9,
Data Loading...
