Thermodynamics of small platinum clusters

Sebetci, Ali; Güvenç, Zi̇ya B.; Kökten, Hatice

doi:10.1016/j.commatsci.2004.08.016

Cited by 8 publications

(7 citation statements)

References 32 publications

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“…However, for clusters and nanoparticles ranging in size from several atoms to thousands of atoms, the transition from one equilibrium phase to another equilibrium phase occurs gradually in a wider temperature range. 6,11,12,22,23 Within this range the two phases are in equilibrium with each other. Therefore, the phase change in finite systems has to be characterized by two temperatures, T 1 and T 2 with T 2 > T 1 .…”

Section: Introductionmentioning

confidence: 96%

“…In a strict sense, since the transition is gradual, there is no melting point at all. Since clusters and nanoparticles are often a mixture of many isomers with similar energies equilibrating with each other, 6,18,22,23,29,37,[45][46][47][48] their melting transitions have the same ambiguity. The distinction between clusters and nanoparticles is not strict, and we use the generic name particles to refer to both of them.…”

Section: Introductionmentioning

confidence: 99%

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Nanosolids, Slushes, and Nanoliquids: Characterization of Nanophases in Metal Clusters and Nanoparticles

Truhlar

2008

J. Am. Chem. Soc.

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One of the keys to understanding the emergent behavior of complex materials and nanoparticles is understanding their phases. Understanding the phases of nanomaterials involves new concepts not present in bulk materials; for example, the phases of nanoparticles are quantum mechanical even when no hydrogen or helium is present. To understand these phases better, molecular dynamics (MD) simulations on size-selected particles employing a realistic analytic many-body potential based on quantum mechanical nanoparticle calculations have been performed to study the temperature-dependent properties and melting transitions of free Al n clusters and nanoparticles with n = 10-300 from 200 to 1700 K. By analyzing properties of the particles such as specific heat capacity (c), radius of gyration, volume, coefficient of thermal expansion (beta), and isothermal compressibility (kappa), we developed operational definitions of the solid, slush, and liquid states of metal clusters and nanoparticles. Applying the definitions, which are based on the temperature dependences of c, beta, and ln kappa, we determined the temperature domains of the solid, slush, and liquid states of the Al n particles. The results show that Al n clusters ( n or= 19, diameter of more than 1 nm) do have a melting transition and are in the liquid state above 900-1000 K. However, all aluminum nanoparticles have a wide temperature interval corresponding to the slush state in which the solid and liquid states coexist in equilibrium, unlike a bulk material where coexistence occurs only at a single temperature (for a given pressure). The commonly accepted operational marker of the melting temperature, namely, the peak position of c, is not unambiguous and not appropriate for characterizing the melting transition for aluminum particles with the exception of a few particle sizes that have a single sharp peak (as a function of temperature) in each of the three properties, c, beta, and ln kappa.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Nanosolids, Slushes, and Nanoliquids: Characterization of Nanophases in Metal Clusters and Nanoparticles

Truhlar

2008

J. Am. Chem. Soc.

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“…For comparison purposes, the few theoretical onset transition temperatures of small (<100 atoms) transition-metal NPs (metal = Au, Pt, Ni, Pd, and Ag) found in the literature are given here: T m = 525 K for Ag 55 , 40 700 K for Ni 85 , 41 908 K for Pd 55 , 42 900 K for Pt 19 , 43 and 300 K for Au 54 . 44 The comparison of these results with those from Figure 5 is difficult because the geometry, number of atoms, and interaction model used were different in both cases, with the exception of Ni 85 , where at least the number of atoms were the same and a better agreement is found.…”

Section: Phase Transitionsmentioning

confidence: 99%

The Concept of Localized Atomic Mobility: Unraveling Properties of Nanoparticles

2014

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The concept of short time scale mean-square displacement (MSD) was used to get a picture of the distribution of atomic mobilities in different layers and regions of Au and Pt nanoparticles (NPs). The NPs were simulated in vacuum at different temperatures using molecular dynamics and the embedded-atom model. The calculated atomic mobilities were greater for atoms located at corner positions, followed by atoms on edges and planes, independently of the layer analyzed. The short time scale MSD was revealed to be an excellent alternative to predict melting temperatures of small (<100 atoms) transition-metal NPs. Finally, the combination of classical (MSD) and quantum (density of states) properties brought some insight into how the catalytic activity may locally change over the NP surface. The trends found for subnanometer-sized NPs indicate that corner, kinks, and defect regions play a major role for the catalytic activity of these particles.

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“…[17]. He atoms were used as buffer gas, with Pt-He and He-He interactions described by Lennard-Jones potential 6 …”

Section: MD Simulationsmentioning

confidence: 99%

“…And Pt, Rh and Pd have been used very extensively in heterogeneous catalysis, especially for reactions involving CO and H 2 . To predict stable configuration of Pt nanoparticles, theoretical simulations have been focused on the potential energy and thermal evolution [4][5][6]. In theoretical point of view, the growth and isomerization of nanoparticles belong to thermal-driven atomic migrations.…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of thermodynamic balance between cluster isomers and statistical model for predicting isomerization rate

Lin

2013

J Nanopart Res

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-By molecular dynamics simulations and free energy calculations based on MonteCarlo method, the detailed balance between Pt cluster isomers was investigated. For clusters of n≤50, stationary equilibrium is achieved in 100 ns in the canonical ensemble, while longer time is needed for n>50. Then, a statistical mechanical model was built to evaluate unimolecular isomerization rate and simplify the prediction of isomer formation probability. This model is simpler than transition state theory and can be easily applied on ab initio calculations to predict the lifetime of nanostructures.

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Thermodynamics of small platinum clusters

Cited by 8 publications

References 32 publications

Nanosolids, Slushes, and Nanoliquids: Characterization of Nanophases in Metal Clusters and Nanoparticles

Nanosolids, Slushes, and Nanoliquids: Characterization of Nanophases in Metal Clusters and Nanoparticles

The Concept of Localized Atomic Mobility: Unraveling Properties of Nanoparticles

Theoretical investigation of thermodynamic balance between cluster isomers and statistical model for predicting isomerization rate

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