Melting of Nanocrystalline Gold

We report atomistic simulations of the melting of nanocrystalline gold with mean grain sizes from 1.7 to 23 nm. Analysis of the structural changes near melting point at the atomic scale confirms that in the melting process, the solid–liquid interface sweeps rapidly from grain boundary into inner grain as the temperature increases. We find a linear relation between the melting point and the reciprocal grain size for the larger grain size samples, above 7.7 nm, similar to the observations in nanoparticles. However, based on the critical Lindemann ratio, the grain boundaries in these cases should be liquefied at very low temperature (less than 800 K for grain size of 9.7 nm). At a small grain size, this relation between grain size and melting temperature was broken. In particular, at grain sizes below 4 nm, the melting point was found to be approximately constant. It was proposed that the growth and/or merging of grains at low temperature far from melting was contributed to this observation