Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Thermodynamical Properties of Pd-Au and Pt-Au Core-Shell Nanoparticles:
A Molecular Dynamics Study
S. Kaya 1 , S.Ozdemir Kart 1* , T. Cag 2
1
2
Department of Chemical Engineering, Texas A&M University, Texas, TX 77843-3122, USA
Abstract- The thermodynamical properties of Pt-Au and Pd-Au core-shell nanoparticles are studied at constant temperature and constant
volume (TVN) molecular dynamics simulations with the use of quantum corrected Sutton-Chen potential energy function. The nanoparticles
have the spherical core-shell structures with two different diameters of 5 nm and 10 nm. The spherical Pd or Pt is covered with the spherical
Au shell with five different concentrations. The pure metals (Pd, Pt and Au) with the same particle sizes are also studied to compare with the
results of core-shell nanoparticles. The melting temperature is determined by examining the behaviour of the total energy as a function of the
temperature. Simulation results such as kinetic energy, potential energy, heat capacity, and latent heat of the fusion are presented. The effects
of the concentration of shell atoms on the physical properties for both core-shells interested in this study are also investigated.
In recent years, metallic nanoparticles attract growing
interest due to their unique properties -differing greatly
fro m bulk- resulting fro m the large fraction of surface
atoms. Furthermore, core-shell nanoparticles are of
particular interest in applications ranging from catalysis to
optical, magnetic and electronic applications because the
properties of nanoparticles can change with not only size
and but also chemical composition [1-4]. Core-shell
nanoparticles are made up of core material coated with
another material. The design of new nanoparticle
functionalized with size, composition and atomic
distribution necessitate the understanding of the structure
and properties of core-shell nanoparticles. In this study, we
are particularly interested in the thermodynamic and
structural properties of both Pd-Au and Pt-Au core-shell
nanoparticles. We have performed molecular dynamics
simulations for five different core-shell concentrations by
utilizing Quantum Sutton-Chen potential [5-6]. They are
arranged as Pd(Pt) n-xAu x , where, n is the mu ltip lier of the
lattice parameter to produce the radius of the
nanoparticles. Here, n is taken as 6 and 12, respectively,
for 5 nm and 10 nm core-shells while x is set as 0, 1, …6
for the small size core-shell and 0, 2, 4, … 12 for the large
size of the one. The total energy, melting temperature,
specific heat and latent heat of the fusion are calculated as
a function of temperature and concentrations. Atomic
distribution of these core-shell nanoparticles at various
temperatures are shown in Figure 1. Melting temperatures
of the core-shell nanoparticles increase with not only the
size of the spherical nanoparticles, but also the number of
the core atoms of Pd or Pt. Core atoms such as Pd coated
by Au are redistributed among the Au shell atoms at high
temperature as shown in Figure 1. c) and d).
Figure 1. Typical snapshop of Pd 4 Au 2 core-shell paricles: halfdisplayed
a)- 300K, b) 1200 K, c) 2000 K and d) full-structure
displayed at 2000K
*Corresponding author: ozsev@pau.edu.tr
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[6] H H Kart, G. Wang, I. Karaman an
(2009).
a) 300 K
b) 1200 K
c) 2000 K d) 2000 K
6th Nanoscience and Nanotechnology Conference, zmir, 2010 256