Phase transitions at the nanoscale: freezing/melting and structural changes in nanoparticles

Christoph Dellago (Faculty of Physics, University of Vienna)
pén., 2013-04-19 14:00
063-as terem

Under suitable conditions, first order phase transitions such as the freezing of a liquid or the structural transformation of a solid occur via a nucleation and growth mechanism, in which a nucleus of the stable phase is formed in the metastable phase. For systems with sizes in the nanometer regime, the nucleation mechanism and its kinetics are strongly affected by finite size effects. I will address this issue using melting/freezing of gold nanoparticles and the Wurtzite-to-rocksalt transition in CdSe nanocrystals as illustrative examples. Based on the results of transition path sampling simulations, I provide a picture of the transition mechanism paying particular attention to the structure of the critical nuclei. The role of the reaction coordinate in the investigation of the transition mechanism is discussed.