**Metastability of multitwinned Ag nanorods: Molecular dynamics study**

J Monk and JJ Hoyt and D Farkas, PHYSICAL REVIEW B, 78, 024112 (2008).

DOI: 10.1103/PhysRevB.78.024112

Nanoscale rods have been shown to exhibit a multiple twinned structure.
The rods grow along a **110**-type crystallographic direction and have a
pentagonal cross section with five (111) twins connecting the wire
center to the corners of the pentagon. Here, we use molecular dynamics
simulations with an embedded atom method interatomic potential for Ag to
compute the ground-state energies of the multitwinned rods and compare
with the bulk equilibrium crystal shape, as estimated from a Wulff
construction. The excess energy of the nontwinned equilibrium nanorods
and the multitwinned nanorods was obtained as a function of the wire
length (L) as well as the cross sectional area (A(cs)). Various
contributions to the total energy, such as twin boundary energy and
surface energies, are discussed and included in an analytical model that
compares favorably with the simulation results. Our results show that
for infinitely long nanowires with A(cs)< 1500 nm(2), the nontwinned
structure is always energetically favorable. However, if the energy of
the dipyramidal atomic structure at the nanorod ends is included in the
model then the twinned nanorods are stable with respect to the
nontwinned rods below a critical aspect ratio (L/root A(cs)).

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