Riccardo Ferrando &
Francesca Baletto talk with ScienceWatch.com and
answer a few questions about this month's Emerging Research
Front Paper in the field of Chemistry. The authors
have also sent along images of their work.
Article: Structural properties of nanoclusters:
Energetic, thermodynamic, and kinetic
effects
Authors: Baletto,
F;Ferrando, R
Snapshots from a computer
simulation of the freezing of a
silver nanodroplet. The nanodroplet,
made of several hundred atoms, starts
in the liquid state at high
temperature (left picture). Upon
cooling down, the nanodroplet
solidifies as a face centered cubic
nanoparticle with a stacking fault
(right picture).
Figure 2:
Figure 2:
Snapshots from a computer
simulation of the growth of a
nanoparticle composed by
C60 molecules (each sphere
is a molecule). Starting from a
low-symmetry structure (left
picture), newly added molecules cause
the formation of a highly symmetric
cluster of decahedral structure
(right picture), with symmetric
islands on its top (molecules in the
islands are depicted in yellow).
Decahedral structures are
non-cystalline. They cannot be found
in bulk solids, but they are
frequently formed in nanoclusters.
This is an example of the much wider
structural variety of nanoparticles
with respect to bulk
matter.
Figure 3:
Figure 3:
Typical behavior of the
structural transitions from
icosahedral to decahedral to
face-centered-cubic structures with
increasing size N. The latter are
crystalline structures, which
resemble pieces of bulk crystal,
while icosahedra and decahedra cannot
be found in bulk crystals. As size
increases, the most favorable
structures (identified by the lowest
excess energy
?) pass from the
quasi-spherical but highly strained
icosahedra, to the less compact but
less strained decahedra and finally
to crystalline clusters, which are
not strained but far from a spherical
shape. Transition sizes from
icosahedra to decahedra and from
decahedra to crystalline structures
are indicated.