Multiscale Modeling of Agglomerated Ceria Nanoparticles: Interface Stability and Oxygen Vacancy Formation

Abstract

The interface formation and its effect on redox processes in agglomerated ceria nanoparticles (NPs) have been investigated using a multiscale simulation approach with standard density functional theory (DFT), the self-consistent-charge density functional tight binding (SCC-DFTB) method, and a DFT-parameterized reactive force-field (ReaxFF). In particular, we have modeled Ce40O80 NP pairs, using SCC-DFTB and DFT, and longer chains and networks formed by Ce40O80 or Ce132O264 NPs, using ReaxFF molecular dynamics simulations. We find that the most stable (111)/(111) interface structure is coherent whereas the stable (100)/(100) structures can be either coherent or incoherent. The formation of (111)/(111) interfaces is found to have only a very small effect on the oxygen vacancy formation energy, Evac. The opposite holds true for (100)/(100) interfaces, which exhibit significantly lower Evac values than the bare surfaces, despite the fact that the interface formation eliminates reactive (100) facets. Our results pave the way for an increased understanding of ceria NP agglomeration. © 2019 Kim, Kullgren, Wolf, Hermansson and Broqvist.