ReaxFF Molecular Dynamics Simulations of Large Gold Nanocrystals

A systematic study
of gold nanocrystals is carried out using molecular dynamics simulations
with reactive force fields. The nanocrystal size is varied between
2 and 10 nm with methane and butane thiolate as ligands. The reactive
force fields allow investigation of the formation of staples. The
simulations explain several experimental observations such as the
number of staples per thiolate of about 40% and the occupation of
the top adsorption sites on the facets. They also show that the frequency
of staples is increased on the edges, which leads to a desorption
of gold atoms from the nanocrystal edges. In contrast to previous
nonreactive simulations, no difference between the distances of the
ligands on the nanocrystal edges and facets is observed. Except for
the 2 nm particles, the nanocrystal size and the alkane chain length
of the ligands have only a small influence on the nanocrystal properties.
The occupation of adsorption sites and staple frequencies are very
slowly converging properties, taking more than ns.