Onuki Akira
Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
J Chem Phys. 2009 Mar 28;130(12):124703. doi: 10.1063/1.3089709.
Equilibrium properties of dilute binary fluid mixtures are studied in two-phase states on the basis of a Helmholtz free energy including the gradient free energy. The solute partitioning between gas and liquid (Henry's law) and the surface tension change Delta gamma are discussed. A derivation of the Gibbs law Delta gamma = -T Gamma is given with Gamma being the surface adsorption. Calculated quantities include the derivatives dT(c)/dX and dp(c)/dX of the critical temperature and pressure with respect to the solute molar fraction X and the temperature-derivative (partial derivative gamma/partial derivative T)(cx,p) of the surface tension at fixed pressure p on the coexistence surface. Here (partial derivative gamma/partial derivative T)(cx,p) can be both positive and negative, depending on the solute molecular size and the solute-solvent interaction, and diverges on the azeptropic line. Explicit expressions are given for all these quantities in the van der Waals model.
基于包含梯度自由能的亥姆霍兹自由能，研究了稀二元流体混合物在两相状态下的平衡性质。讨论了气体和液体之间的溶质分配（亨利定律）以及表面张力变化Δγ。给出了吉布斯定律Δγ = -TΓ的推导，其中Γ为表面吸附。计算量包括临界温度和压力相对于溶质摩尔分数X的导数dT(c)/dX和dp(c)/dX，以及在共存表面上固定压力p下表面张力的温度导数(∂γ/∂T)(cx,p)。这里(∂γ/∂T)(cx,p)可以为正也可以为负，这取决于溶质分子大小和溶质 - 溶剂相互作用，并且在恒沸线上发散。在范德瓦尔斯模型中给出了所有这些量的显式表达式。
