Experimentally measured [(a)–(c)] and computed [(d)–(f)] particle configurations in a 2D dusty plasma, matched for defect fraction. Larger dots show lattice defects inside the circle , dark gray (blue online) for particles with five nearest neighbors and light gray (red online) for seven neighbors. Experimentally measured configurations previously identified (Ref. 7) as (a) 1.6% amplitude modulation, “hot” crystal, (b) 2.2% a.m., hexatic phase and (c) 2.8% a.m., liquid. Computed configurations, identified as (d) , hot crystal, (e) , hexatic phase, and (f) , liquid phase.
Pair correlation functions for values of the coupling parameter spanning the melting transition. Successive curves are each shifted downward by 1/2. The translational correlation length decreases abruptly between and 77.7, indicating a transition from a crystalline phase to a hexatic phase.
Bond-orientational correlation function plotted on (a) linear axes and (b) semilog axes. Three distinct regimes can be seen. For the system displays a roughly linear decay in . For and 69.9 the decay goes as , as shown by the dashed line. For the decay is exponential. Symbols are experimentally measured curves (Ref. 7) for amplitude modulation levels of 1.6% (diamonds), 2.2% (circles), and 2.8% (triangles).
(a) Dependence of fraction of defects on the coupling parameter , where a defect is defined as a particle with five or seven nearest neighbors. (b) The average lattice constant and rms variation in the lattice constant vs . Note the suppressed zero on the left vertical axis, so that varies by only .
(a) Translation and orientational correlation lengths and , respectively, vs the coupling parameter . Here undergoes an abrupt decrease for the crystal-to-hexatic transition, indicating a loss of translational order, while undergoes an abrupt decrease for the hexatic-to-liquid transition, indicating the loss of orientational order. (b) Average value of the bond orientational correlation function [Eq. (14)] vs , plotted on semilog axes.
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