Reversed size-dependent stabilization of ordered nanophases

Pirart, Jérome; Front, Alexis; Rapetti, Daniele; Andreazza‐Vignolle, C.; Andreazza, Pascal; Mottet, C.; Ferrando, Riccardo

doi:10.1038/s41467-019-09841-3

Cited by 52 publications

(54 citation statements)

References 27 publications

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“…This is effect becomes nonnegligible for very small nanoparticles (~2-3 nm in size) i.e. clusters [82][83][84]. The large curvature of small nanoparticles is responsible of the strain which gives a volume contribution into the excess Gibbs energy of nanoparticles.…”

Section: Phase Diagrams Of Npsmentioning

confidence: 99%

Advances in thermodynamic modelling of nanoparticles

Guisbiers

2019

Advances in Physics: X

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Among all the computational techniques (Density Functional Theory, Molecular Dynamics, Monte-Carlo Simulations, Nanothermodynamics) used to investigate the properties of nanoparticles, nanothermodynamics is the most unusual one. Indeed, most people still thing that thermodynamics does not apply at the nanoscale; nonetheless, thermodynamic concepts can still be applied at the nanoscale to predict various properties of nanoparticles like melting temperature, energy bandgap . . . In this review, we first introduce the fundamental concepts and methods of nanothermodynamics starting from Hill's contributions to the most recent developments focusing specifically on the relationship between the material property and the following parameters as quantum statistics (Fermi-Dirac or Bose-Einstein), size and shape of the nanoparticle. ARTICLE HISTORY

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Section: Phase Diagrams Of Npsmentioning

confidence: 99%

Advances in thermodynamic modelling of nanoparticles

Guisbiers

2019

Advances in Physics: X

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“…Specifically, the study of growth processes in very clean environments, such as the gas phase [7], is essential to unravel the dominant pathways leading to the growth of nanoparticles of different shapes. These studies often take advantage of combined experiment-simulation efforts [8][9][10][11][12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Octahedral Growth of PtPd Nanocrystals

et al. 2021

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PtPd nanoparticles are among the most widely studied nanoscale systems, mainly because of their applications as catalysts in chemical reactions. In this work, a combined experimental-theoretical study is presented about the dependence of growth shape of PtPd alloy nanocrystals on their composition. The particles are grown in the gas phase and characterized by STEM-HRTEM. PtPd nanoalloys present a bimodal size distribution. The size of the larger population can be tuned between 3.8 ± 0.4 and 14.1 ± 2.0 nm by controlling the deposition parameters. A strong dependence of the particle shape on the composition is found: Pd-rich nanocrystals present more rounded shapes whereas Pt-rich ones exhibit sharp tips. Molecular dynamics simulations and excess energy calculations show that the growth structures are out of equilibrium. The growth simulations are able to follow the growth shape evolution and growth pathways at the atomic level, reproducing the structures in good agreement with the experimental results. Finally the optical absorption properties are calculated for PtPd nanoalloys of the same shapes and sizes grown in our experiments.

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“…The less intense stabilization of the ordered inner-phase L1 1 with increasing the NPs size is consistent with the reversed size-dependent stabilization of the L1 1 ordering observed for AgPt NPs. 16 However, stabilization of the L1 1 ordering with respect to LEH ones for AgPt NPs (see Table 2 for values and Figure S1 for structures) was calculated to be several times stronger, 17 indicating a notably decreased propensity of AgPd NPs to form the peculiar L1 1 ordering compared to analogous AgPt NPs.…”

Section: Resultsmentioning

confidence: 98%

“…15 However, an intriguing counterexample to this trend has been recently demonstrated by the formation of a peculiar ordered layered phase L1 1 inside AgPt NPs smaller than 2.5 nm, whereas in larger NPs the ordering disappeared. 16 The L1 1 - phase stabilization in small NPs was associated with the formation of a monolayer-thick Ag outermost shell preventing Pt from occupying surface sites. This Ag shell has been calculated to exert increasing stress on the L1 1 layered domains with increasing particle size making the alternating −Ag–Ag– and −Pt–Pt– layers energetically unfavorable, when the NP exceeds the critical size of ca.…”

Section: Introductionmentioning

confidence: 99%

AgPd, AuPd, and AuPt Nanoalloys with Ag- or Au-Rich Compositions: Modeling Chemical Ordering and Optical Properties

et al. 2021

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Bimetallic nanoparticles have a myriad of technological applications, but investigations of their chemical and physical properties are precluded due to their structural complexity. Here, the chemical ordering and optical properties of AgPd, AuPd, and AuPt nanoparticles have been studied computationally. One of the main aims was to clarify whether layered ordered phases similar to L1 1 one observed in the core of AgPt nanoparticles [ Pirart J. Pirart J. 1982 31040272 Nat. Commun. 2019 10 ] are also stabilized in other nanoalloys of coinage metals with platinum-group metals, or the remarkable ordering is a peculiarity only of AgPt nanoparticles. Furthermore, the effects of different chemical orderings and compositions of the nanoalloys on their optical properties have been explored. Particles with a truncated octahedral geometry containing 201 and 405 atoms have been modeled. For each particle, the studied stoichiometries of the Ag- or Au-rich compositions, ca. 4:1 for 201-atomic particles and ca. 3:1 for 405-atomic particles, corresponded to the layered structures L1 1 and L1 0 inside the monatomic coinage-metal skins. Density functional theory (DFT) calculations combined with a recently developed topological (TOP) approach [ Kozlov S. M. Kozlov S. M. 29218158 Chem. Sci. 2015 6 3868 3880 ] have been performed to study the chemical ordering of the particles, whose optical properties have been investigated using the time-dependent DFT method. The obtained results revealed that the remarkable ordering L1 1 of inner atoms can be noticeably favored only in small AgPt particles and much less in AgPd ones, whereas this L1 1 ordering in analogous Au-containing nanoalloys is significantly less stable compared to other calculated lowest-energy orderings. Optical properties were found to be more dependent on the composition (concentration of two metals) than on the chemical ordering. Both Pt and Pd elements promote the quenching of the plasmon.

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Reversed size-dependent stabilization of ordered nanophases

Cited by 52 publications

References 27 publications

Advances in thermodynamic modelling of nanoparticles

Advances in thermodynamic modelling of nanoparticles

Octahedral Growth of PtPd Nanocrystals

AgPd, AuPd, and AuPt Nanoalloys with Ag- or Au-Rich Compositions: Modeling Chemical Ordering and Optical Properties

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