نویسندگان

چکیده

در این مقاله سیستمهای دوبعدی از دیدگاه نظری, تجربی و شبیه سازی کامپیوتری مورد بررسی قرار گرفته و سپس مراحل انجام شبیه سازی دینامیک مولکولی تشریح شده است. ذوب یک بلور نمک یونی دوبعدی را توضیح داده و نتایج شبیه سازی سیستمهایی با 16, 64 و 256 ذره ارایه می گردد. نتایج نشان می دهد که گذار ذوب مورد شبیه سازی از نوع مرتبه اول است. سیستم مورد شبیه سازی را پس از ذوب گرم کرده و سپس مایع گرم را سرد کرده تا منجمد شود, که در این دما سیستم به ساختار بلوری بر میگردد.

کلیدواژه‌ها

عنوان مقاله [English]

Molecular dynamics simulation of a two-dimensional system

نویسندگان [English]

  • S. M. Huseini
  • S. M. Amini

چکیده [English]

  The study of a two-dimensional (2-D) system started nearly half a century ago when Peierls and Landau showed the lack of long range translational order in a two-dimensional solid. In 1968, Mermin proved that despite the absence of long range translational order. Two-dimensional solids can still exhibit a different kind of long range bond orientation. During the last decade, fascinating theories were put forward to explain the role of topological defects in the melting of two-dimensional solids, starting with Kosterlitz and Thouless. Recent surge of interest in melting is also due to the theoretical ideas of Halperin, Nelson and Young. They have suggested that the transition may be fundamentally different from that observed in ordinary three-dimensional systems. Computer simulations suggest that the transition is of the usual first-order type observed in a three-dimensional system. A large body of experimental and simulation research into the two-dimensional melting followed the announcement of the KTHNY theory. In spite of all this effort, the question as to the nature of two dimensional melting remains unresolved. Recent experimental work supporting the existence of continuous melting transitions in some two-dimentsional systems indicates the need for further theoretical and computational work to lead to an understanding of the experimental results.   In this paper we intend to summarze and clarify the current situation with regard to research in the two-dimensional melting with an emphasis on computer simulations. The paper begins with an overview of the current status of relevant theoretical, experimental and simulation research, then a two-dimensional simulation of an ionic salt system is studied in detail. This simulation has been done by using the molecular dynamics method. The most important parameters that have been determined are ,The trnsition temperature, the total energy of the system, the mean square displacement and the bond angle distribution The transtion temperature of the system has been specified by plotting some of these parameters as a function of temperature and time. The first order transition is observed. It is difficult to distinguish a hexatic phase from a two-phase coexistence region.

کلیدواژه‌ها [English]

  • simulation
  • two dimensional melting
  • molecular dynamics

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