Computer simulations of a two-dimensional system with competing interactions.
Computer simulations of a two-dimensional system with competing interactions.
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具有竞争性相互作用的二维系统的计算机模拟。
DOI：
10.1103/physreve.65.036706
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
S. J. Singer
中科院分区：
文献类型：
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作者：
A. Stoycheva;S. J. Singer
本文报道了具有长程相互作用的二维偶极伊辛模型的大规模计算机模拟的结果和方法。研究了多达117，649个粒子的系统，以阐明二维系统的基本激发和相图，例如朗缪尔单层，薄石榴石膜和固体表面上的吸附膜，它们自发地形成条纹，气泡和中间形状的域的图案。通过结合快速多极方法和非Metropolis Monte Carlo抽样技术，对低温下具有长程相互作用的大尺度系统进行了具有挑战性的数值研究。我们的模拟提供的证据表明，在足够高的比例的排斥吸引力的耦合常数的模型，在感兴趣的系统中的双重条纹顺序是通过缺陷介导的机制丢失。热容数据和我们模拟中观察到的系统无序的激发表明，它最有可能是一个Kosterlitz无相变的实例。有外场和无外场的模拟结果与解析标度理论[A. D. Stoycheva和S. J.Singer，Phys.Rev.E64，016118（2001）]，证实了由分析模型提供的相图。标度理论表明，在一定条件下，缺陷介导的条纹熔化可能会取代伊辛像条纹内的无序小排斥强度。一个模型，支持这两种无序机制的定性讨论。
The results and methodology of large scale computer simulations of the two-dimensional dipolar Ising model with long-range interactions are reported. Systems as large as 117,649 particles were studied to elucidate the elementary excitations and phase diagram of two-dimensional systems, such as Langmuir monolayers, thin garnet films, and adsorbed films on solid surfaces, which spontaneously form patterns of stripes, bubbles, and intermediately shaped domains. The challenging numerical investigations of large scale systems with long-range interactions at low temperatures were made possible by combining the fast multipole method and a non-Metropolis Monte Carlo sampling technique. Our simulations provide evidence that, at sufficiently high ratios of the repulsive to the attractive coupling constant for the model, twofold stripe order in the systems of interest is lost through a defect-mediated mechanism. Heat capacity data and the excitations observed in our simulations as the system disorders indicate that it is most likely an instance of a Kosterlitz-Thouless phase transition. The results from simulations with and without external field are in excellent agreement with the predictions of an analytic scaling theory [A. D. Stoycheva and S. J. Singer, Phys. Rev. E 64, 016118 (2001)], confirming the phase diagram furnished by the analytic model. The scaling theory suggests that, under certain conditions, defect-mediated stripe melting may be supplanted by Ising like disordering within stripes for small repulsion strength. A qualitative discussion of a model that supports both disordering mechanisms is presented.