流体相平衡模拟计算的一种新方法——等概率扰动法

A NEW METHOD FOR SIMULATION OF PHASEEQUILIBRIA——EQUAL PROBABILITY PERTURBATIONMONTE CARLO METHOD

根据统计力学的等概率假设,本文提出一种新的扰动分子的方法——等概率扰动法,以产生Monte Carlo模拟中的Markov链.新方法可以在1个盒子里同时模拟包括界面区域在内的流体相平衡,并且对纯流体,模拟只需在正则系综里进行即可.应用该方法,模拟计算了纯方阱流体在不同温度下的汽液共存密度、沿高度方向上的密度分布图及化学位等.研究表明,传统的Metropolis位移技术不适于模拟此类非均相体系.

A new scheme based on the fundamental postulation in statistical mechanics for perturbating molecules to create the Markov chain in Monte Carlo calculation was proposed. The new method can be used to simulate, in only a single box, phase equilibria of fluids including interfaces. Furthermore, for pure fluids, simulation can be implemented simply in the canonical ensemble. Simulation of pure square - well fluid at different temperatures by applying our new method gave the coexistence densities of bulk phases, the density profiles and chemical potentials along the z axis. In addition, our present study shows that the traditional Metropolis technique is not suitable to the simulation of such heterogeneous systems.