Lennard-Jones流体气液相图的粒子交换分子动力学模拟研究

Studies on Gas-liquid Phase Diagram of Lennard-Jones Fluid via Particle Exchange Molecular Dynamics Simulation

利用粒子交换分子动力学模拟方法 (Particle exchange molecular dynamics,PEMD)研究了 Lennard-Jones流体的气液相图 .模拟中 ,用两个耦合箱分别代表液相和气相 .通过直接比较两箱的粒子化学势来控制交换粒子 ,从而达到两相平衡 .采用 Widom方法计算化学势 .两模拟箱平衡时具有相同的温度、压强和粒子化学势 .模拟的气液相图结果与利用其它方法得到的 Lennard-Jones流体气液相图符合得很好 .

A Particle Exchange Molecular Dynamics(PEMD) simulation method is proposed to study the gas-liquid phase diagram of Lennard-Jones fluid. In the simulation, two coupled boxes are adopted to represent the gas phase and the liquid phase, respectively. The equilibrium is achieved via exchanging particles between two simulation boxes only by direct comparison of their respective chemical potentials, which are calculated by using Widom method. Finally, two coupled simulation boxes possess the same temperature, pressure and particle chemical potential. The resulted gas-liquid phase diagram is in good agreement with that obtained by using other methods.