Zhou Shiqi
State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083, China.
J Chem Phys. 2009 Oct 7;131(13):134702. doi: 10.1063/1.3242717.
To surpass a traditional mean field density functional approximation for a perturbation term of interparticle potential function in liquid state, a correlation term is introduced by using weighted density approximation to deal with the perturbation free energy beyond the mean field one. Consequently, a free energy density functional approximation is advanced by combining the mean field term and correlation term with a hard sphere term treated with a Lagrangian theorem-based density functional approximation in the present work. The present free energy density functional approximation is applied in the framework of classical density functional theory (DFT) to a hard core attractive Yukawa (HCAY) fluid subject to external fields; comparison of the resulted predictions for density profiles with available simulation data is favorable for the present DFT approach as a highly accurate predictive approach. Then, the DFT approach is employed to investigate influencing factors for solvation forces between two infinite planar surfaces immersed in an intervening solvent with the HCAY potential function. It is found that (i) critical fluctuations induce negative adsorptions and long-ranged solvation forces; (ii) for narrow slit, the effect of external potential range is kept down; instead strength of the external field contact potential plays dominating role; (iii) state point in the bulk phase diagram, where the most remarkable critical effects are displayed, is the one with a bulk density a little higher than the critical density; remnants of critical fluctuations remain close to the bulk gas-liquid coexistence curve.
为了超越传统的平均场密度泛函近似来处理液态中粒子间势函数的微扰项，通过使用加权密度近似引入一个关联项，以处理超出平均场的微扰自由能。因此，在本工作中，通过将平均场项和关联项与基于拉格朗日定理的密度泛函近似处理的硬球项相结合，提出了一种自由能密度泛函近似。将当前的自由能密度泛函近似应用于经典密度泛函理论（DFT）框架下的受外场作用的硬核吸引 Yukawa（HCAY）流体；将所得密度分布预测结果与现有模拟数据进行比较，结果表明当前的 DFT 方法是一种高度准确的预测方法。然后，采用 DFT 方法研究了浸入具有 HCAY 势函数的中间溶剂中的两个无限平面表面之间的溶剂化力的影响因素。研究发现：（i）临界涨落会导致负吸附和长程溶剂化力；（ii）对于窄缝，外势范围的影响受到抑制；相反，外场接触势的强度起主导作用；（iii）体相相图中的状态点，即显示出最显著临界效应的点，是体密度略高于临界密度的点；临界涨落的残余部分仍靠近体气液共存曲线。
