Simulation des systèmes fortement couplés à deux dimensions par la méthode de Monte Carlo : étude structurelle et transitions de phase

Abstract

Numerical simulations based on the Monte Carlo method are conducted to investigate ground-state configurations and phase transitions of strongly coupled dust particles. The interparticle potential between negatively charged dust particles is modeled by Coulomb, Yukawa and logarithmical potential and in the presence of two dimensional parabolic confinement potential for a system with a restricted number of particles N=30 and low temperature, at which a crystalline structure characterized by shell structure exists. The effect of random charge fluctuation is taken into account for a dominant charging process by particles collection. Charge fluctuation is found to modify the ground-state configurations, leading the system to exhibit structural transitions that are more effective when particles interact through logarithmic potential. The new simple expression of charge fluctuation is considered and characterized by a charged amplitude calculated using the approach of Khrapak et al. Both parameters, temperature and charge fluctuation amplitude, are used to explore the rich microscopic behaviours of the non-linear mesoscopic classical system in the case of coulomb potential. The clusters undergo structural transitions, which manifest as phase transitions of first or second order with respect to the parameter T and charge fluctuation. The first transition corresponds to inter-shell rotations, while the second one corresponds to melting or disorder. Moreover, the melting temperature depends on the charge amplitude, that is, for lower amplitude of the charge, the system exhibits a shell structure until a critical temperature T m, where the melting occurs. This temperature decreases when the charge amplitude increases as a result of particles’ strong repulsive interaction.