Monte Carlo calculation of phase separation in a two-dimensional Ising system

Journal of Statistical Physics - Monte Carlo calculations were carried out for a two-dimensional Ising model of a binary alloy with nearest-neighbor attractive interactions between like atoms. The...     

Monte Carlo simulation of two-dimensional Ising model with logarithmic exchange interaction

Monte Carlo simulation was done to a 2-D Ising model with exchange interaction depending logarithmically on distance. This model is equivalent to a 2-D Coulomb gas.A configuration corresponding to bound pairs of opposite charges appears below T_c, while above T_c pairs are dissolved into free charges.     

Monte Carlo simulation of a random-field Ising antiferromagnet

Phase transitions in the three-dimensional diluted Ising antiferromagnet in an applied magnetic field are analyzed numerically. It is found that random magnetic field in a system with spin concentration below a certain threshold induces a crossover from second-order phase transition to first-order transition to a new phase characterized by a spin-glass ground state and metastable energy states at finite temperatures.     

Monte Carlo simulation of three-dimensional dilute Ising model

A multispin coding program for site-diluted Ising models on large simple cubic lattices is described in detail. The spontaneous magnetization is computed as a function of temperature, and the critical temperature as a function of concentration is found to agree well with the data of Marro et al.⁽⁴⁾ and Landau⁽³⁾ for smaller systems.The first successful epsilon expansion seems to be by D. E. Khmelnitskii,ZhETF 68:1960 (1975), English translationSov. Phys. JETP 41:981 (1975); for numerical estimates see K. E. Newman and E. K. Riedel,Phys. Rev. H25:264 (1982), for experiments see R. J. Birgenau, R. A. Cowley, G. Shirane and H. Yoshizawa,J. Stat. Phys. 34:817 (1984).     

Monte Carlo simulation of Ising model on decagonal covering structure

We study the Ising model on a two-dimensional quasilattice developed from the decagonal covering structure. The periodic boundary conditions are applied to a patch of rhombus-like covering pattern. By means of the Monte Carlo simulation and the finite-size scaling analysis the critical temperature is estimated as 2.317±0.002. Two critical exponents are obtained being 1/v=0.992±0.003 and η=0.247±0.002, which are close to the values of the two-dimensional regular lattices as well as the Penrose tilings.     

Phase transitions in a two-dimensional vortex system with defects: Monte Carlo simulation

AbstractThe phase states and phase transitions in a system consisting of a two-dimensional vortex lattice with defects are studied by the Monte Carlo method. It is shown that a “rotating lattice” phase, which is an intermediate phase between the vortex crystal and vortex liquid phases, is present. The dependence of the temperature of the transition from the rotating lattice phase into a vortex liquid on the strength of the defect potential is determined. The current-voltage characteristics of the system are calculated at various temperatures for point, square, and linear defects. It is shown that the phase state of the system strongly affects its transport properties.     

Monte Carlo simulation of very large kinetic Ising models

We study the relaxation of Ising models in three and four dimensions aboveT _c , using multi-spin coding for lattices up to 360³ and 40⁴. The nonlinear relaxation time diverges as (T–T _c )^{–1.05±0.04} in three dimensions, where corrections to scaling are taken into account. In four dimensions the effective exponent is about 0.72; logarithmic correction factors make the analysis difficult here. The linear relaxation time for the asymptotic exponential decay is found to be larger, with effective exponents 1.31 (d=2) and 0.97 (d=4). The difference in the linear and nonlinear relaxation exponents is compatible in three dimensions with the orderparameter exponent , as predicted by Racz.Work supported by SFB 125 Aachen-Jülich-KölnWork started at Department de Physique des Systemes Desordonnes, Universite de Provence, Centre St-Jerome, F-13397 Marseille Cedex 13, France     

Monte Carlo simulation of cluster kinetics in three-dimensional Ising model

Simulations in lattices of size 100³ at the critical point of the three-dimensional Glauber kinetic Ising model indicate that the 1935 Becker-Doring equation no longer works there: The growth rates decay in time. These conclusions confirm those in two dimensions.     

Monte Carlo study of an Ising gauge system

The phase diagram of the 3-d Ising gauge model with additional ferromagnetic nearest neighbour Ising coupling is explored by Monte Carlo simulations.     

Monte Carlo simulation of Ising models by multispin coding on a vector computer

Rebbi's efficient multispin coding algorithm for Ising models is combined with the use of the vector computer CDC Cyber 205. A speed of 21.2 million updates per second is reached. This is comparable to that obtained by special- purpose computers.     

Monte Carlo simulation of a kinetic Ising model of the glass transition

Results of Monte Carlo experiments for the two-spin facilitated kinetic Ising model on a cubic lattice are presented and compared with a theoretical prediction.     

Monte Carlo simulation of the two-dimensional planar model

We present results for the two-dimensional planar model on the square lattice. We have developed a Monte Carlo routine which is more efficient than the single-spin-flip algorithms used previously. We report on the variation of the following quantities with temperature: specific heat, energy, magnetization, susceptibility, correlation function, helicity modulus, the density of vortex/ antivortex pairs, the average distance between a vortex and its nearest antivortex, and the average distance between a vortex/antivortex pair and the nearest pair. Our results are in excellent agreement with the reliable results reported in the literature and are in accord with the general features of the Kosterlitz-Thouless theory.     

H2在二维共价有机骨架上吸附的蒙特卡罗模拟研究

使用巨正则蒙特卡罗方法预测H2分子在六种具有不同结构和组分的二维共价有机骨架材料(2D COFs)中的物理吸附行为.研究结果表明:(1)在所研究的温度和压力范围内,ILCOF-1表现出最优异的氢存储性能,是目前2D COFs中储氢量最高的材料之一;其它5种COFs的储氢量低于其它2D COFs中储氢量较高的COF-5,-8,-10和TP-COF,而与COF-1,-6和Pc-PBBA COF相差不多.(2)与3D COFs相比,本文所研究的所有COFs的储氢量均低于目前储氢量最高的COF-105和COF-108;除ILCOF-1外,其它5种COFs材料均低于COF-102和COF-103.根据模拟计算的结果,分析了表面积、孔直径和等量吸附热等因素对COFs储氢性能的影响.对COFs储氢能力的强化提出了一些建设性意见.