Dynamic structure in supported Pt nanoclusters: Real-time density functional theory and x-ray spectroscopy simulations

Vila, Fernando D.; Rehr, J. J.; Kas, J. J.; Nuzzo, Ralph G.; Frenkel, Anatoly I.

doi:10.1103/physrevb.78.121404

Cited by 84 publications

(143 citation statements)

References 21 publications

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“…Thus, there is a minimum in the encapsulation energy of TM m inside C n as a function of the TM m size for a particular value of n. For TM m @C 80 , our encapsulated TM m clusters were not large enough to reach a minimum in the encapsulation energy; however, our results indicate that the same trends can be obtained. These results lead to the following question: Why is the stability larger for TM 3 and TM 4 than for TM 2 ? From our analysis, we found that the number of TM atoms that bind to the inside C n surface plays a crucial role in increasing the stability of the TM m @C n systems.…”

Section: Encapsulation Energymentioning

confidence: 99%

“…For example, Rh, Pd, and Pt particles supported on oxides such as CeO 2 (Refs. 1 and 2) and Al 2 O 3 are widely used in catalysis, 3,4 Au nanorods have been studied for selective release of drugs, 5 Rh nanoparticles (NPs) confined inside carbon nanotubes (CNTs) have been studied for ethanol production from syngas, 6 and Co NPs inside CNTs have been studied for tailoring the band gap of CNTs. 7 Furthermore, magnetic iron-oxide NPs and rare-earth atoms have been investigated as contrast agents for magnetic resonance imaging, 8,9 which is important for cancer therapy.…”

Section: Introductionmentioning

confidence: 99%

“…All those studies can be separated into three groups, namely, TM particles supported on oxides, 3,4 protected by ligands, 5 and encapsulated inside fullerenes and CNTs. 6,7 Thus, for real applications, clusters and NPs are in direct contact with an external environment, which can affect their atomic structure, relative stability, magnetic moments, and optical properties compared with isolated TM m clusters.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Encapsulation of small magnetic clusters in fullerene cages: A density functional theory investigation within van der Waals corrections

Tereshchuk

Silva

2012

Phys. Rev. B

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The encapsulation of magnetic transition-metal (TM) clusters inside carbon cages (fullerenes, nanotubes) has been of great interest due to the wide range of applications, which spread from medical sensors in magnetic resonance imaging to photonic crystals. Several theoretical studies have been reported; however, our atomistic understanding of the physical properties of encapsulated magnetic TM 3d clusters is far from satisfactory. In this work, we will report general trends, derived from density functional theory within the generalized gradient approximation proposed by Perdew, Burke, and Ernzerhof (PBE), for the encapsulation properties of the TM m @C n (TM = Fe, Co, Ni; m = 2−6, n = 60,70,80,90) systems. Furthermore, to understand the role of the van der Waals corrections to the physical properties, we employed the empirical Grimme's correction (PBE + D2). We found that both PBE and PBE + D2 functionals yield almost the same geometric parameters, magnetic and electronic properties, however, PBE + D2 strongly enhances the encapsulation energy. We found that the center of mass of the TM m clusters is displaced towards the inside C n surfaces, except for large TM m clusters (m = 5 and 6). For few cases, e.g., Co 4 and Fe 4 , the encapsulation changes the putative lowest-energy structure compared to the isolated TM m clusters. We identified few physical parameters that play an important role in the sign and magnitude of the encapsulation energy, namely, cluster size, fullerene equatorial diameter, shape, curvature of the inside C n surface, number of TM atoms that bind directly to the inside C n surface, and the van der Waals correction. The total magnetic moment of encapsulated TM m clusters decreases compared with the isolated TM m clusters, which is expected due to the hybridization of the d-p states, and strongly depends on the size and shape of the fullerene cages.

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Section: Encapsulation Energymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Encapsulation of small magnetic clusters in fullerene cages: A density functional theory investigation within van der Waals corrections

Tereshchuk

Silva

2012

Phys. Rev. B

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“…Metal nanoparticles (NPs) have been shown to display anomalous electronic and thermodynamic properties, including metal to non-metal transitions, 1, 2 superheating, 3 and negative thermal expansion [4][5][6][7] . However, despite decades of intense research, the origin of these effects is still heavily debated.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic properties of Pt nanoparticles: Size, shape, support, and adsorbate effects

et al. 2011

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“…1,2,8 These approaches are based on calculating EXAFS spectral contribution from each atom in the cluster, and then performing temporal averaging of the results. As this and other approaches continue to evolve, the need for a good experimental model against which to judge theoretical treatments has become critical.…”

Section: Introductionmentioning

confidence: 99%

A theoretical and experimental examination of systematic ligand-induced disorder in Au dendrimer-encapsulated nanoparticles

Yancey¹,

Chill

Zhang

et al. 2013

Chem. Sci.

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In this paper we present a new methodology for the analysis of 1-2 nm nanoparticles using extended X-ray absorption fine structure (EXAFS) spectroscopy. Different numbers of thiols were introduced onto the surfaces of dendrimer-encapsulated Au nanoparticles, consisting of an average of 147 atoms, to systematically tune the nanoparticle disorder. An analogous system was investigated using density functional theory molecular dynamics (DFT-MD) simulations to produce theoretical EXAFS signals that could be directly compared to the experimental results. Validation of the theoretical results by comparing to experiment allows us to infer previously unknown details of structure and dynamics of the nanoparticles. Additionally, the structural information that is learned from theoretical studies can be compared with traditional EXAFS fitting results to identify and rationalize any errors in the experimental fit. This study demonstrates that DFT-MD simulations accurately depict complex experimental systems in which we have control over nanoparticle disorder, and shows the advantages of using a combined experimental/theoretical approach over standard EXAFS fitting methodologies for determining the structural parameters of metallic nanoparticles.

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Dynamic structure in supported Pt nanoclusters: Real-time density functional theory and x-ray spectroscopy simulations

Cited by 84 publications

References 21 publications

Encapsulation of small magnetic clusters in fullerene cages: A density functional theory investigation within van der Waals corrections

Encapsulation of small magnetic clusters in fullerene cages: A density functional theory investigation within van der Waals corrections

Thermodynamic properties of Pt nanoparticles: Size, shape, support, and adsorbate effects

A theoretical and experimental examination of systematic ligand-induced disorder in Au dendrimer-encapsulated nanoparticles

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