Non equilibrium effects in fragmentation

Abstract

We study, using molecular dynamics techniques, how boundary conditions affect the process of fragmentation of finite, highly excited, Lennard-Jones systems. We analyze the behavior of the caloric curves (CC), the associated thermal response functions (TRF) and cluster mass distributions for constrained and unconstrained hot drops. It is shown that the resulting CC's for the constrained case differ from the one in the unconstrained case, mainly in the presence of a ``vapor branch''. This branch is absent in the free expanding case even at high energies . This effect is traced to the role played by the collective expansion motion. On the other hand, we found that the recently proposed characteristic features of a first order phase transition taking place in a finite isolated system, i.e. abnormally large kinetic energy fluctuations and a negative branch in the TRF, are present for the constrained (dilute) as well the unconstrained case. The microscopic origin of this behavior is also analyzed.

21 pages, 11 figures

Cited by in corpus (12)

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• Partial energies fluctuations and negative heat capacities
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• Enhancement of kinetic energy fluctuations due to expansion
• Connection between the Largest Lyapunov Exponent, Density Fluctuation and Multifragmentation in Excited Nuclear Systems
• The role of Coulomb interaction in fragmentation
• Time dependence of critical behavior in multifragmentation
• Dynamics and thermodynamics of fragment emission from excited sources
• Extended Gibbs ensembles with flow
• Expansion dynamics of Lennard-Jones systems