Monte Carlo Simulation of Phase Separation Behavior in a Cu-Co Alloy Nanoparticle
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Byeong-Joo Lee Materials Evaluation Center, Korea Research Institute of Standards and Science, Yusong P.O. Box 102, Taejon 305-600, Korea
Jae-Pyoung Ahn, Young Whan Cho,a) and Jong-Ku Park Nano-materials Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea (Received 24 October 2001; accepted 5 February 2002)
The phase separation behavior in a Cu–Co nanoparticle was investigated using Monte Carlo (MC) simulation. The modified embedded atom method (MEAM) was adopted to describe the interatomic potentials for the Cu–Co alloy system. Some of the cross potential parameters were fitted with experimental data such as mixing enthalpy and lattice constants of Cu–Co alloys. The present MC simulation combined with the MEAM potential describes well the phase separation between face-centered-cubic (fcc) Cu and fcc Co during the annealing of the particle.
Atomistic simulations such as molecular dynamics and Monte Carlo simulation play an important role in materials science by providing a physical insight into the phenomena occurring in materials and allowing the prediction of material properties. First-principles calculation is recognized as an ideal approach to understanding the interatomic behavior of condensed matters. However, it can currently deal with a few hundred atoms at most, which is too small to attack most of materials problems. Molecular dynamics and Monte Carlo (MC) simulation combined with semi-empirical atomic potentials can deal with more atoms than first-principles calculation by several orders. In this case, the reliability of the simulation result depends mainly on atomic potentials. Among various semi-empirical atomic potentials, the embedded atom method (EAM) potential1,2 has been actively employed in a wide range of applications, as it can successfully reproduce various physical properties of elements such as elastic, structural, defect, surface, and thermal properties. The modified embedded atom method (MEAM) potential3,4 is a different version of the EAM potential. Using a common formalism, the MEAM potential can describe not only face-centered-cubic (fcc) elements but also hexagonal-close-packed (hcp), bodycentered-cubic (bcc), and diamond cubic elements that
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 5, May 2002
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exhibit the directionality of atomic bonding. This enables the MEAM potential to be highly applicable to alloy systems. The Cu–Co system has received much attention because it exhibits giant magnetoresistance (GMR) behavior when fabricated as multilayered thin films or nanoparticles. The purpose of the present study was to investigate the atomic behavior of a Cu–Co alloy nanoparticle during annealing using MC simulation. The MEAM was adopted to describe the interatomic potential for the Cu– Co alloy system. The procedure for the determination of alloy MEAM potential parameters to describe the alloy system was outlined. In MEAM, the total energy of a sys
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