Octahedral Growth of PtPd Nanocrystals

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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Adsorption of helium on a charged propeller molecule: hexaphenylbenzene

The European Physical Journal D ◽

10.1140/epjd/s10053-021-00301-6 ◽

2021 ◽

Vol 75 (11) ◽

Author(s):

Siegfried Kollotzek ◽

Florent Calvo ◽

Serge Krasnokutski ◽

Fabio Zappa ◽

Paul Scheier ◽

...

Keyword(s):

Mass Spectra ◽

Theoretical Study ◽

Crystalline Solid ◽

Aromatic Rings ◽

Helium Nanodroplets ◽

Helium Atoms ◽

Dissociation Energies ◽

Propeller Blades ◽

Dynamics Simulations ◽

Good Agreement

Abstract Physisorption on planar or curved graphitic surfaces or aromatic rings has been investigated by various research groups, but in these studies, the substrate was usually strictly rigid. Here, we report a combined experimental and theoretical study of helium adsorption on cationic hexaphenylbenzene (HPB), a propeller-shaped molecule. The orientation of its propeller blades is known to be sensitive to the environment, with substantial differences between the molecule in the gas phase and in the crystalline solid. Mass spectra of He$$_{n}$$ n HPB$$^{+}$$ + , synthesized in helium nanodroplets, indicate enhanced stability for ions containing $$n = 2, 4, 14, 28, 42, 44$$ n = 2 , 4 , 14 , 28 , 42 , 44 , or 46 helium atoms. Path-integral molecular dynamics simulations reveal a significant dependence of the dissociation energy on the details of the HPB geometry. Good agreement between the experimental data and calculated dissociation energies is obtained, provided that the symmetry of HPB$$^{+}$$ + is reduced from $$D_{6}$$ D 6 to $$D_{2}$$ D 2 , such a lower symmetry being suggested from quantum chemical calculations as arising upon electron removal. Graphic Abstract

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Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44457 ◽

2011 ◽

Author(s):

Toshihiro Kaneko ◽

Kenji Yasuoka ◽

Ayori Mitsutake ◽

Xiao Cheng Zeng

Keyword(s):

Molecular Dynamics ◽

Heat Capacity ◽

Transition Temperature ◽

Peak Position ◽

Temperature Curve ◽

Dynamics Simulation ◽

Lennard Jones ◽

Dynamics Simulations ◽

First Time ◽

Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

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Efficient Numerical Evaluation of Thermodynamic Quantities on Infinite (Semi-)classical Chains

Journal of Statistical Physics ◽

10.1007/s10955-021-02736-y ◽

2021 ◽

Vol 182 (3) ◽

Author(s):

Christian B. Mendl ◽

Folkmar Bornemann

Keyword(s):

Transfer Operator ◽

Classical System ◽

Free Energy Density ◽

Classical Particle ◽

Thermodynamic Quantities ◽

Nls Equation ◽

Classical Systems ◽

Particle Chain ◽

Dynamics Simulations ◽

Good Agreement

AbstractThis work presents an efficient numerical method to evaluate the free energy density and associated thermodynamic quantities of (quasi) one-dimensional classical systems, by combining the transfer operator approach with a numerical discretization of integral kernels using quadrature rules. For analytic kernels, the technique exhibits exponential convergence in the number of quadrature points. As demonstration, we apply the method to a classical particle chain, to the semiclassical nonlinear Schrödinger (NLS) equation and to a classical system on a cylindrical lattice. A comparison with molecular dynamics simulations performed for the NLS model shows very good agreement.

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Explanation of the Influence of Inflow Air Content on the Lift of Cavitating Hydrofoils

Journal of Fluids Engineering ◽

10.1115/1.4039252 ◽

2018 ◽

Vol 140 (8) ◽

Cited By ~ 1

Author(s):

Eduard Amromin

Keyword(s):

Experimental Data ◽

Theoretical Study ◽

Lift Coefficient ◽

Cavity Surface ◽

Air Bubbles ◽

Incoming Flow ◽

Fluid Density ◽

Air Content ◽

Theoretical Results ◽

Good Agreement

According to several known experiments, an increase of the incoming flow air content can increase the hydrofoil lift coefficient. The presented theoretical study shows that such increase is associated with the decrease of the fluid density at the cavity surface. This decrease is caused by entrainment of air bubbles to the cavity from the surrounding flow. The theoretical results based on such explanation are in a good agreement with the earlier published experimental data for NACA0015.

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Size-Dependent Elasticity of Silicon Nanowires

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.60-61.315 ◽

2009 ◽

Vol 60-61 ◽

pp. 315-319 ◽

Cited By ~ 3

Author(s):

W.W. Zhang ◽

Qing An Huang ◽

H. Yu ◽

L.B. Lu

Keyword(s):

Molecular Dynamics ◽

Molecular Dynamics Simulations ◽

Silicon Nanowires ◽

First Principles ◽

Si Nanowires ◽

Size Dependent ◽

Reconstructed Surfaces ◽

Strain Relationship ◽

Dynamics Simulations ◽

Good Agreement

Molecular dynamics simulations are carried out to characterize the mechanical properties of [001] and [110] oriented silicon nanowires, with the thickness ranging from 1.05nm to 3.24 nm. The nanowires are taken to have ideal surfaces and (2×1) reconstructed surfaces, respectively. A series of simulations for square cross-section Si nanowires have been performed and Young’s modulus is calculated from energy–strain relationship. The results show that the elasticity of Si nanowires is strongly depended on size and surface reconstruction. Furthermore, the physical origin of above results is analyzed, consistent with the bond loss and saturation concept. The results obtained from the molecular dynamics simulations are in good agreement with the values of first-principles. The molecular dynamics simulations combine the accuracy and efficiency.

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Computer-Generated Structural Models for a-Si:H

MRS Proceedings ◽

10.1557/proc-141-71 ◽

1988 ◽

Vol 141 ◽

Author(s):

Laurent J. Lewis ◽

Normand Mousseau ◽

FranÇois Drolet

Keyword(s):

Molecular Dynamics ◽

Boundary Conditions ◽

Amorphous Silicon ◽

Periodic Boundary ◽

Hydrogenated Amorphous Silicon ◽

Structural Models ◽

Periodic Boundary Conditions ◽

Dynamics Simulations ◽

Hydrogenated Amorphous ◽

Good Agreement

AbstractA new algorithm for generating fully-coordinated hydrogenated amorphous silicon models with periodic boundary conditions is presented. The hydrogen is incorporated into an a-Si matrix by a bond-switching process similar to that proposed by Wooten, Winer, and Weaire, making sure that four-fold coordination is preserved and that no rings with less than 5 members are created. After each addition of hydrogen, the structure is fully relaxed. The models so obtained, to be used as input to molecular dynamics simulations, are found to be in good agreement with experiment. A model with 12 at.% H is discussed in detail.

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