Journal of Statistical Physics

, Volume 145, Issue 4, pp 812-830

First online:

Combining Rare Events Techniques: Phase Change in Si Nanoparticles

  • Sergio OrlandiniAffiliated withConsorzio Interuniversitario per le Applicazioni di Supercalcolo Per Università e Ricerca (CASPUR)Dipartimento di Chimica, Università “Sapienza”
  • , Simone MeloniAffiliated withSchool of Physics, University College DublinConsorzio Interuniversitario per le Applicazioni di Supercalcolo Per Università e Ricerca (CASPUR) Email author 
  • , Giovanni CiccottiAffiliated withSchool of Physics, University College DublinDipartimento di Fisica and CNISM, Università “Sapienza”

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We describe a combined Restrained MD/Parallel Tempering approach to study the difference in free energy as a function of a set of collective variables between two states in presence of metastabilities in the manifold orthogonal to the one spanned by the chosen collective variables. We illustrate the method by an extended study of the relative stability of the amorphous vs crystalline Si nanoparticles embedded in a-SiO2 of size ranging between 0.8 and 1.8 nm as a function of temperature [S. Orlandini, S. Meloni, and L. Colombo in Phys. Rev. B 83:235303, 2011]. The results show that the method permits to get over the hidden metastabilities. Finally, we try to identify the missing collective variables from the Restrained MD/Parallel Tempering trajectories and analyze whether the collective variable used to control the amorphous-to-crystalline transition is adequate to describe the mechanism of crystallization of some of the nanoparticles considered.


Rare events Restrained MD Parallel Tempering Si nanoparticles Order-disorder phase transition