Structure and dynamics of finite three-dimensional Yukawa clusters in complex plasmas : Newtonian versus Langevin Dynamics

TL;DR

This study compares Newtonian and Langevin Dynamics simulations of three-dimensional Yukawa clusters in complex plasmas, revealing differences in inter-shell correlations, particle mobility, and rotational motion.

Contribution

It provides a detailed comparison of static and dynamic properties of Yukawa clusters using two simulation methods, highlighting the effects of friction on cluster behavior.

Findings

Inter-shell angular correlations differ between LD and fMD.

Particle mobility is higher in Langevin Dynamics.

Rotational motion diminishes with increased friction.

Abstract

The structure and dynamics of a harmonically confined three dimensional finite dust cluster are investigated via both Langevin Dynamics (LD) and frictionless Molecular Dynamics (fMD) simulation. The static structure of the system is analyzed through the Radial Distribution Function, Center-two-particle correlation function(C2P) and angular correlation function. The intra-shell angular correlation, Radial Distribution Function and C2P remains largely unaffected by the dynamics employed. However, the inter-shell angular correlation exhibits sharp peaks at irregular angular intervals in fMD which are not seen in LD indicating strongly correlated motion of the two spherical shells in the cluster in fMD. The single particle dynamics of the cluster is characterized by the Van - Hove self autocorrelation function and Mean Squared Displacement (MSD). Notably, the Van - Hove autocorrelation function in fMD simulations exhibits narrower width and higher peak height as compared to the LD simulations, suggesting greater particle mobility in LD. Trajectory analysis reveals a rotational motion of the particles about a common axis in fMD which disappears with progressively increasing friction coefficient. We show that the disappearance of rotational motion with the introduction of neutral friction in the dynamics is due to the much faster relaxation of the interparticle distance as well as interparticle angular separation in LD as compared to fMD.