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Fig. 7 Atomically resolved STEM-HAADF and BF images of the Au-Pd interface. Simulta-
neously acquired (a) STEM-HAADF and (b) STEM-BF images of an Au
core
Pd
shell
nanorod, with
(c) line intensity profiles taken as indicated in (a). Reproduced from [
51
]. Reproduced by
permission of the Royal Society of Chemistry.
[For the electronic version:
http://dx.doi.org/
computer simulations to assist with the analysis and interpretation of the experi-
mental results. In addition to the AuPd and AuRh systems mentioned above, we
have also considered the related AuPt system, for which structural and chemical
studies have recently been carried out [
82
,
83
].
6.2 Simulations of Deposition of Rh, Pd and Pt on Au
Surfaces
The characteristic length of metal-coated nanorods is of the order of tens of
nanometres. Modelling of deposition on flat surfaces should therefore be represen-
tative of the key processes occurring at the interface between the nanorod and the
coating material during the process of deposition.
The computational studies reported below are based on molecular dynamic
(MD) simulations, using the Gupta potential, of the deposition of metal atoms,
Rh, Pd or Pt, onto an Au surface (henceforth denoted M/Au), in order to explore the
initial stages of interfacial structure formation in these systems. The most instruc-
tive crystallographic orientations for simulation are the two low-index {111} and
{100} orientations, because they typically have the lowest surface energies.
The Gupta potential parameter sets adopted for our simulations were taken from
the literature. The Rh and Au parameters were taken from [
63
,
84
]forRhandAu,
respectively, and the mixed interaction parameters were fitted to experimental disso-
lution energies of each element in a matrix of the other [
77
] (Ferrando R (2013)
Personal communication). The AuPd parameters were taken from [
85
,
86
]. Finally,
the Au and Pt parameters were taken from [
63
], while the heteronuclear AuPt
parameters were derived as the mean of the corresponding Au and Pt parameters [
70
].
The Nos
ยด
-Hoover thermostat [
87
] was applied in all MD simulations in order to
maintain a constant temperature throughout the deposition process. Au {100} and
