Cooling-rate effects in simple monatomic amorphous nanoparticles

Abstract

Cooling-rate effects in simple monatomic amorphous nanoparticles were studied in a spherical model containing 2469 atoms using a molecular dynamics (MD) method under non-periodic boundary conditions. We used the pair double-well interaction potential developed by Engel and Trebin [Phys. Rev. Lett. 98 225505 (2007)]. To observe the cooling-rate effects, the initial, well-relaxed models at a high temperature (i.e. in liquid state) were cooled to zero temperature at three different cooling rates. Cooling-rate effects on thermodynamic quantities, such as potential and surface energy, were more pronounced than those for static quantities. The potential and surface energy of the nanoparticles decreased with decreasing cooling rate, indicating the formation of more stable configurations with lower cooling rates. The microstructure of amorphous nanoparticles was analyzed via radial distribution function (RDF), coordination number and bond-angle distributions. Relatively weak cooling-rate effects on such quantities were found. Honeycutt–Andersen analysis for different bond pairs was used and discussed. The microstructure of the surface and core of amorphous nanoparticles were analyzed and the evolution of nanoparticle structures upon cooling from the melt discussed. Cooling-rate effects in a short-range interaction system are discussed and compared with those in long-range systems.