ReaxFF Molecular Dynamics Simulations of Large Gold Nanocrystals

A systematic study of gold nanocrystals is carried outusing molecular dynamics simulations with reactive forcefields. Thenanocrystal size is varied between 2 and 10 nm with methane andbutane thiolate as ligands. The reactive forcefields allow investigationof the formation of staples. The simulations explain severalexperimental observations such as the number of staples per thiolateof about 40% and the occupation of the top adsorption sites on thefacets. They also show that the frequency of staples is increased on theedges, which leads to a desorption of gold atoms from the nanocrystaledges. In contrast to previous nonreactive simulations, no differencebetween the distances of the ligands on the nanocrystal edges andfacets is observed. Except for the 2 nm particles, the nanocrystal sizeand the alkane chain length of the ligands have only a small influenceon the nanocrystal properties. The occupation of adsorption sites andstaple frequencies are very slowly converging properties, taking more than ns.