带电胶体系统固液相变的分子动力学研究

Molecular dynamics simulations on solid-liquid phase behavior of charged colloidal systems

在修正Yukawa相互作用的基础上,采用常温分子动力学方法数值研究了带电胶体系统的大离子屏蔽效应和多分散性效应对其固液边界的影响。研究结果发现,在屏蔽长度较大时,固液相变曲线出现了明显偏差。初步定性认为这种相边界偏差现象来自于系统多体效应的增强。另外,数值研究了固液相变时键接取向序参数的变化。

Based on molecular dynamics with constant temperature, we studied the macroion shielding effect and polydispersity on melting of charged colloidal systems with coarse-grained prescriptions of pointYukawa pair interaction. Compared with the Robbins—Kremer—Grest simulation results, a visible deviation of melting line is observed at small λ, which indicates a large macroion screening length. It issuggested that this deviation of solid-liquid phase behavior is resulted from microscopic many-body effect which is sensitive to the screening parameter. In addition, Q_6, the bond orientation order parameter is studied in Yukawa systems.