Berlin 2014 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 20: Poster Session - Dusty Plasmas
P 20.8: Poster
Mittwoch, 19. März 2014, 16:30–18:30, SPA Foyer
The Triple Correlation Function of spherical dust clusters: structural analysis and phase transition — •Hauke Thomsen, Patrick Ludwig, and Michael Bonitz — ITAP, Christian-Albrechts-Universität, Kiel, D-24098, Germany
Dust particles in a complex plasma usually accumulate a high negative charge inside a plasma which is responsible for their strong repulsive interaction and high coupling. When confined in a parabolic trap, these particles form spherical clusters with a characteristic shell structure.
In recent years the phase transition-like crossover from a crystal to a liquid-like state has attracted high interest, e.g. [1]. While the radial melting is now well understood, here we concentrate on the loss of intra-shell order. The radial pair correlation function ρ(rij) is well suited for homogeneous system but has to be adapted to the spherical symmetry for finite clusters. Here, we present the Triple Correlation function (TCF) as a sensitive tool for the investigation of intra-shell order.
The TCF is calculated from the “bonding angles“ of three particles, a particle triple. This quantity is particularly well suited to investigate the orientational order within spherical cluster shells. The intra-shell bond order of Coulomb balls with several hundreds of particles shows striking similarities with a flat 2D system. At the melting region, the 30∘-peak in bond order between nearest and second-nearest neighbors shows a clear drop.
[1] J. Böning et al., Phys. Rev. Lett. 100, 113401 (2008)