Abstract: Monte Carlo simulations of phase equilibria for lattice polymer systems with chain length r=1,2,4,8 are carried out in the canonical ensemble. All chain molecules are introduced into the cell regularly upon initiation, followed by being perturbed through the repta-tion, end - rotate, crank - shaft and L - flip motions. A cavity biased Widom test particle method was proposed and adopted in calculating the residual chemical potentials at various temperatures and densities. The chemical potential, pressure and compressibility factor of systems are then calculated from the residual chemical potentials through classical thermodynamics. Phase equilibrium coexistence curves are obtained according to the phase equilibrium criteria. Results are compared with those calculated from Flory - Huggins theory, Freeds theory, and Hu et als work. The comparison shows that Hu et als work gives the best prediction, while Flory -Huggins theory shows large discrepancy. Freeds theory also gives satisfactory results, but a little poorer than Hu et als work.

摘要： 应用修正的Widom试验粒子方法在三维立方格子中计算了链节数分别为r=1,2,4,8的链状分子在不同温度、密度下的剩余化学位,然后运用热力学关系计算了以上系统在不同温度、密度下的化学位、压力和压缩因子,并求得系统的相平衡曲线和临界点。模拟结果与Flory-Huggins理论、Freed的格子场理论及胡英等工作的结果进行了比较。发现Freed理论和胡英等的工作都能较好地描述链状分子系统的相平衡行为。