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.
Highlights
Synthesized ceria samples often appear in the form of agglomerates of nanoparticles (NPs) (Wang and Feng, 2003; Mai et al, 2005; Du et al, 2007; Lin et al, 2012; Liu et al, 2015; Schlick et al, 2016; Lykaki et al, 2017)
In Kullgren et al (2017), the DFTB model was subjected to an extended validation process, and passed the test of reproducing the reference density functional theory (DFT) results with respect to NP structures as well as oxygen vacancy formation energies in ceria bulk and at the low-index surfaces
The DFTB model was further validated for some of the interface structures, and we find that calculated energies, such as the interface formation energy, Einterface, and the oxygen vacancy formation energy, Evac, from SCC-DFTB are in reasonably good agreement with those from DFT
Summary
Synthesized ceria samples often appear in the form of agglomerates of nanoparticles (NPs) (Wang and Feng, 2003; Mai et al, 2005; Du et al, 2007; Lin et al, 2012; Liu et al, 2015; Schlick et al, 2016; Lykaki et al, 2017). In Kullgren et al (2017), the DFTB model was subjected to an extended validation process, and passed the test of reproducing the reference DFT results with respect to NP structures as well as oxygen vacancy formation energies in ceria bulk and at the low-index surfaces.
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