A Model for Phase Transition based on Statistical Disassembly of Nuclei at Intermediate Energies

TL;DR

This paper presents a simplified nuclear model demonstrating liquid-gas phase transition behavior in finite particle systems, using statistical disassembly of nuclei with properties akin to nuclear physics, without complex simulations.

Contribution

It introduces a model based on nuclear physics properties that captures phase transition phenomena without requiring Monte Carlo simulations.

Findings

p-ρ isotherms show Maxwell-like behavior

Chemical potential remains constant in the phase transition region

Model obeys Clausius-Clapeyron relations

Abstract

Consider a model of particles (nucleons) which has a two-body interaction which leads to bound composites with saturation properties. These properties are : all composites have the same density and the ground state energies of composites with k nucleons are given by -kW+\sigma k^{2/3} where W and \sigma are positive constants. W represents a volume term and \sigma a surface tension term. These values are taken from nuclear physics. We show that in the large N limit where N is the number of particles such an assembly in a large enclosure at finite temperature shows properties of liquid-gas phase transition. We do not use the two-body interaction but the gross properties of the composites only. We show that (a) the p-\rho isotherms show a region where pressure does not change as $\rho$ changes just as in Maxwell construction of a Van der Waals gas, (b) in this region the chemical potential does not change and (c) the model obeys the celebrated Clausius-Clapeyron relations. A scaling law for the yields of composites emerges. For a finite number of particles N (upto some thousands) the problem can be easily solved on a computer. This allows us to study finite particle number effects which modify phase transition effects. The model is calculationally simple. Monte-Carlo simulations are not needed.