| Summary: | 碩士 === 國立中央大學 === 物理研究所 === 97 === We use molecular dynamics (MD) simulation to investigate the micro-structure and motion of the 2D Coulomb crystals and liquids confined in straight mesoscopic channels about a few inter-particle distances in width. It has been reported that the tight confinement can induce layered structure associated with slow dynamics. However, the small gap does not always guarantee better ordering. The commensurability, a characteristic of system in straight confinement, has to be considered. Tuning the particle number can affect the micro-structure and packing. If the particle number makes the system width commensurate with the natural crystal, the system exhibits -layer isotropic triangular lattice in which the bond length is a constant. Adding extra particles can destroy the commensurability and generate intrinsic defects (IDs). If the extra particles cannot induce the transition to layer structure, the horizontal layers parallel to the confinement get extra particles, leading to shorter horizontal bond length and larger inter-layer spacings. Thus the incommensurate system exhibits anisotropic structure. Another incommensurate structure with layers is observed when the particle number in a layer is fewer than that in the commensurate one. IDs can be generated if the particle number is not an integer multiples of the layer number. IDs form an edge dislocation to connect two adjacent layers consisting different particle numbers. In addition to the micro-structure, we also investigate heat and stress induced micro-motions in different types of packing. The worse interlocking between particles around ID region or in incommensurate structure makes easier structural rearrangements and generates thermal defects. The stress induced stick-slip motions of IDs and particles, and the defect turbulence are also presented and discussed.
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