3 research outputs found
Topological defect motifs in two-dimensional Coulomb clusters
The most energetically favourable arrangement of low-density electrons in an
infinite two-dimensional plane is the ordered triangular Wigner lattice.
However, in most instances of contemporary interest one deals instead with
finite clusters of strongly interacting particles localized in potential traps,
for example, in complex plasmas. In the current contribution we study
distribution of topological defects in two-dimensional Coulomb clusters with
parabolic lateral confinement. The minima hopping algorithm based on molecular
dynamics is used to efficiently locate the ground- and low-energy metastable
states, and their structure is analyzed by means of the Delaunay triangulation.
The size, structure and distribution of geometry-induced lattice imperfections
strongly depends on the system size and the energetic state. Besides isolated
disclinations and dislocations, classification of defect motifs includes defect
compounds --- grain boundaries, rosette defects, vacancies and interstitial
particles. Proliferation of defects in metastable configurations destroys the
orientational order of the Wigner lattice.Comment: 14 pages, 8 figures. This is an author-created, un-copyedited version
of an article accepted for publication in J. Phys.: Condens. Matter. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from it. The definitive
publisher-authenticated version is available online at
10.1088/0953-8984/23/38/38530
Configurational entropy of Wigner crystals
We present a theoretical study of classical Wigner crystals in two- and
three-dimensional isotropic parabolic traps aiming at understanding and
quantifying the configurational uncertainty due to the presence of multiple
stable configurations. Strongly interacting systems of classical charged
particles confined in traps are known to form regular structures. The number of
distinct arrangements grows very rapidly with the number of particles, many of
these arrangements have quite low occurrence probabilities and often the
lowest-energy structure is not the most probable one. We perform numerical
simulations on systems containing up to 100 particles interacting through
Coulomb and Yukawa forces, and show that the total number of metastable
configurations is not a well defined and representative quantity. Instead, we
propose to rely on the configurational entropy as a robust and objective
measure of uncertainty. The configurational entropy can be understood as the
logarithm of the effective number of states; it is insensitive to the presence
of overlooked low-probability states and can be reliably determined even within
a limited time of a simulation or an experiment.Comment: 12 pages, 8 figures. This is an author-created, un-copyedited version
of an article accepted for publication in J. Phys.: Condens. Matter. IOP
Publishing Ltd is not responsible for any errors or omissions in this version
of the manuscript or any version derived from it. The definitive
publisher-authenticated version is available online at
10.1088/0953-8984/23/7/075302.