Molecular dynamics study of surface nucleation and growth mechanism in Cu-based CuPtPd ternary alloy system

https://doi.org/10.1016/j.ssc.2021.114307Get rights and content

Highlights

  • The tendency of crystallization increase with increasing of annealing temperature.

  • The surface nucleation is occurred for CuPtPd system at lower annealing temperatures.

  • The volume nucleation and two-dimensional growth occur in Cu70Pt20Pd10 system at 500 K.

Abstract

This study report that a classical molecular dynamics (MD) simulation method has been performed to investigate the nucleation and growth mechanism from amorphous matrix of Cu-based CuPtPd ternary alloy system with different Pt and Pd addition at nano-scale. The Embedded Atom Method (EAM) utilizing the Sutton-Chen (SC) version is used to calculate interatomic interactions as a semi-empirical potential energy function. The crystallization stages have been examined by using computational method at different annealing temperatures using Johnson-Mehl-Avrami-Kolmogorov (JMAK) equations. The structural developments of systems are analysed with radial distribution function (RDF). Crystallized fractions (x) against annealing time have been calculated from the crystal-type bonded pairs based on Honeycutt-Andersen (HA) cluster analysis index. It is found that an increase in annealing temperature of systems plays important role for crystallization. In addition, the surface nucleation and one-dimensional growth are favourable for low Cu compositions in the CuPtPd system at low annealing temperatures. These findings shed new light on understanding the crystallization kinetics of CuPtPd system by using computer simulation method.

Introduction

The use of CuPtPd alloys attracts a considerable interest scientific and technological area due to their highest electrocatalytic ability [1,2]. Hence, these catalysts are very useful performance for synthesis methods [2]. However, because these methods are expensive precursors including complex process in the literature it is difficult to obtain of these catalysts [[2], [3], [4], [5]]. In addition to catalysts properties, in recent years, the investigation of the phase equilibria and the crystal lattice structure properties in the CuPtPd system have also received considerable attention [[6], [7], [8]]. Potekaev et al. studied the phase diagram of the CuPtPd system formulated by geometric construction on the basis of topological principles [9]. As seen from three-dimensional diagram of system that the phase equilibrium regions of ternary compounds are characterized with B2 and L11 super alloy lattices where the Pd atoms occupy Cu and Pt atomic positions in the L11 super cell [9].

On the other hand, the studies about CuPtPd ternary alloys in nanoscale are still insufficient theoretically. Especially, the investigations about the isothermal crystallization behaviours from amorphous phase of this alloy are not report. Therefore, the understanding about the nature of these behaviours, such as nucleation and crystal growth, plays a major role to improve the crystallization mechanism inside the amorphous matrix [[10], [11], [12]]. But, the determination of the crystallization behaviours during the annealing is difficult to investigate with experimental methods [[13], [14], [15], [16]].

Last few decades, the computational methods have been of great research interest because the experimental impossibilities can be resolve with these methods [[17], [18], [19], [20], [21]]. Particularly, molecular dynamic (MD) simulations are effective way to eliminate of these insufficiencies and they commonly used for examining the structural and thermodynamical properties of materials [[22], [23], [24]]. MD method offers a facility to observe the structural changes of nanoclusters at the atomic scale [25]. In this context, the SC-EAM are widely used in the MD simulations for metallic systems to determine atomic interactions [25]. However, there have been few studies on surface nucleation and crystallization mechanism of Cu-based CuPtPd ternary alloy system using simulation methods.

In the present paper, the important crystallization stages (nucleation and growth) were studied with molecular dynamic simulation based on EAM potential. The HA cluster-index analysis method at nanoscale was used to understand the effect of these type atomic groups on the nucleation, the crystal growth and the crystallization at different annealing temperatures for many of Cu, Pt and Pd compositions in the CuPtPd system. We want to especially report that the different crystallization kinetics based on experimental measurement techniques are calculated by using simulation method in order to explain details of the nucleation and growth behaviors.

Section snippets

Computational procedure and analysis method

In this study, MD simulation is conducted using Parrinello and Rahman [26] (PR) classical method performed in the normal pressure and temperature ensemble (NPT). The Sutton-Chen (SC) type potential based on the Embedded Atom Method (EAM) [27,28] was used to determine interatomic interactions for ternary CuPtPd alloy system. In this type of EAM consist of two contributions to total energy, ET, including N atoms [28];ET=iEi=i[12jiεijφ(rij)ciεiiρi]φ(rij)=(Aijrij)nρi=jiρ(rij)=ji(Aijrij)m.

Results and discussion

Fig. 3a and b shows the starting lattice structures in the MD box throughout plane layers of C2 (Cu50Pt40Pd10) and C4 (Cu70Pt20Pd10) systems at 300 K. The atomic distributions reflect the phase regions of ternary system with L11 and B2 structure in the CuPtPd model alloy system [6]. On the other hand, we plot the total RDF curves to support the accuracy of the atomic distributions on the MD box for systems.

The RDF analysis is an effective definition for understanding the structural evolution of

Conclusions

The main purpose of this study is to emphasize the important crystallization kinetics such as nucleation and growth processes starting from amorphous matrix during the annealing process of Cu-based CuPtPd ternary alloy with different Pt and Pd concentrations (C1, C2, C3 C4 and C5) by using computational method. In this purpose, the crystallized fractions which formulated JMAK kinetics using experimental tools have been calculated with the usage of the crystal-bonded pairs at nano-scale in JMAK

Credit author statement

Fatih Ahmet Celik: Conceptualization, Methodology, Data curation, Visualization. Ebru Tanboğa Korkmaz: Investigation, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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