Theoretical investigation of (La₄O₆)_n, (La₂Ce₂O₇)_n, and (Ce₄O₈)_n nanoclusters (n=10, 18): Temperature effects and O-vacancy formation

Author(s)

Mocelim, Mauricio ; Santos, Mylena N. ; Bittencourt, Albert F. B. ; Lourenco, Tuanan C. ; Da Silva, Juarez L. F.

• Document type: Journal article
• Source: Journal of Chemical Physics; v. 160, n. 18, p. 14-pg., 2024-05-14.

Abstract

We report a theoretical investigation of temperature, size, and composition effects on the structural, energetic, and electronic properties of the (La4O6)(n), (La2Ce2O7)(n), and (Ce4O8)(n) nanoclusters (NCs) for n = 10, 18. Furthermore, we investigated the single O vacancy formation energy as a function of the geometric location within the NC. Our calculations are based on the combination of force-field molecular dynamics (MD) simulations and density functional theory calculations. We identified a phase transition from disordered to ordered structures for all NCs via MD simulations and structural analysis, e.g., radius changes, radial distribution function, common neighbor analysis, etc. The transition is sharp for La36Ce36O126, La20Ce20O70, and Ce72O144 due to the crystalline domains in the core and less abrupt for Ce40O80, La40O60, and La72O108. As expected, radius changes are abrupt at the transition temperature, as are morphological differences between NCs located below and above the transition temperature. We found a strong dependence on the O vacancy formation energy (E-vac) and its location within the NCs. For example, for La40O60, E-vac decreases almost linearly as the distance from the geometric center increases; however, the same trend was not observed for Ce40O80, while there are large deviations from the linear trend for La20Ce20O70. E-vac has smaller values for Ce40O80 and higher values for La40O60, that is, almost three times, while E-vac has intermediate values for mixed oxides, as expected from weighted averages. Therefore, the mixture of one formula unit of La2O3 with two formula units of CeO2 has the effect of increasing the stability of CeO2 (binding energy), which increases the magnitude of the formation energy of the O vacancy. (AU)

• FAPESP's process: 22/12778-5 - Computational material science applied to the screening of materials
• Grantee: Albert Frederico Barbosa Bittencourt
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 19/23681-0 - From ab initio to continuum methods to the screening of sodium-ion battery materials
• Grantee: Tuanan da Costa Lourenço
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 18/21401-7 - Multi-User Equipment approved in grant 2017/11631-2: cluster computational de alto desempenho - ENIAC
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Multi-user Equipment Program
• FAPESP's process: 22/05652-5 - Polarizable force fields for the Investigation of sodium-ion battery materials
• Grantee: Tuanan da Costa Lourenço
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• FAPESP's process: 20/10532-3 - Study of the structural and energetic properties of nanoligas formed by CeO2-ZrO2 via molecular dynamics calculations
• Grantee: Mylena Novaes Santos
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• FAPESP's process: 17/11631-2 - CINE: computational materials design based on atomistic simulations, meso-scale, multi-physics, and artificial intelligence for energy applications
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Research Grants - Research Centers in Engineering Program
• FAPESP's process: 17/11937-4 - A sustainable path to methane conversion by advanced electrochemical technologies
• Grantee: Fabio Coral Fonseca
• Support Opportunities: Research Grants - Research Centers in Engineering Program