Faceting transition of gold nano materials

                             Yanting Wang

Molecular Dynamics simulations have been performed on gold nanorods to study
the transitions from low-temperature rod crystal towards high-temperature
spherical liquid. It has been found that for various-sized gold nanorods, a
shape transition occurs below melting transition temperature, in which rods 
collapse into a shorter and wider meta-stable state. Structural transitions 
have also been observed to accompany with those morphological transitions.

In order to study the role of surface in those transitions with reduced 
complexity, faceting transition of icosahedral gold clusters has been
analyzed geometrically and energetically. The conclusion can be drawn that
the vertices, edges and facets get rounder with higher temperature and totally
disappear below bulk melting temperature.

The same analysis methods for icosahedral gold clusters have been applied 
to the configurations of gold nanorods. Qualitatively, it has been observed 
that macroscopic shape transformations are intimately connected with the 
faceting transition occuring on the sides of the nanorod.