Department of Physics, North Dakota State University, Fargo, North Dakota 58108, USA.
Department of Physics and Astronomy, Carleton College, Northfield, Minnesota 55057, USA.
J Chem Phys. 2017 Apr 7;146(13):134701. doi: 10.1063/1.4979203.
Yukawa fluids consist of particles that interact through a repulsive or attractive Yukawa potential. A surface tension arises at the walls of the container that encloses the fluid or at the interface between two coexisting phases. We calculate that surface tension on the level of mean-field theory, thereby either ignoring the particle size (ideal Yukawa fluid) or accounting for a non-vanishing particle size through a nonideal contribution to the free energy, exemplified either on the level of a lattice gas (lattice Yukawa fluid) or based on the Carnahan-Starling equation of state (Carnahan-Starling Yukawa fluid). Our mean-field results, which do not rely on assuming small gradients of the particle concentrations, become exact in the limit of large temperature and large screening length. They are calculated numerically in the general case and analytically in the two limits of small particle concentration and close to the critical point for a phase-separating system. For a sufficiently small particle concentration, our predicted surface tension is accurate whereas for a phase boundary, we expect good agreement with exact calculations in the limit of a large screening length and if the mean-field model employs the Carnahan-Starling equation of state.
Yukawa 流体由通过排斥或吸引力 Yukawa 势相互作用的粒子组成。容器壁会产生表面张力，该容器包围着流体，或在共存的两个相之间的界面处产生表面张力。我们根据平均场理论计算表面张力，从而忽略粒子尺寸（理想 Yukawa 流体）或通过对自由能的非理想贡献来考虑非零粒子尺寸，这可以在晶格气体（晶格 Yukawa 流体）的水平上或基于 Carnahan-Starling 状态方程（Carnahan-Starling Yukawa 流体）来实现。我们的平均场结果不依赖于假设粒子浓度的小梯度，在大温度和大屏蔽长度的极限下变得精确。在一般情况下，它们通过数值计算得到，在小粒子浓度和接近相分离系统临界点的两个极限下通过解析计算得到。对于足够小的粒子浓度，我们预测的表面张力是准确的，而对于相界，我们期望在大屏蔽长度的极限下与精确计算以及如果平均场模型采用 Carnahan-Starling 状态方程具有良好的一致性。
