Mountain Raymond D, Harvey Allan H
Chemical Sciences Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899,
Applied Chemicals and Materials Division, National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305, 303-497-3555.
J Solution Chem. 2015 Oct;44(11):2179-2193. doi: 10.1007/s10953-015-0401-6.
Modeling of mineral reaction equilibria and aqueous-phase speciation of C-O-H fluids requires the dielectric constant of the fluid mixture, which is not known from experiment and is typically estimated by some rule for mixing pure-component values. In order to evaluate different proposed mixing rules, we use molecular dynamics simulation to calculate the dielectric constant of a model HO-CO mixture at temperatures of 700 K and 1000 K at pressures up to 3 GPa. We find that theoretically based mixing rules that depend on combining the molar polarizations of the pure fluids systematically overestimate the dielectric constant of the mixture, as would be expected for mixtures of nonpolar and strongly polar components. The commonly used semiempirical mixing rule due to Looyenga works well for this system at the lower pressures studied, but somewhat underestimates the dielectric constant at higher pressures and densities, especially at the water-rich end of the composition range.
对矿物反应平衡及C - O - H流体水相形态进行建模需要知道流体混合物的介电常数，而该常数无法通过实验获得，通常是根据混合纯组分值的某种规则来估算。为了评估不同的混合规则，我们使用分子动力学模拟来计算在温度为700 K和1000 K、压力高达3 GPa条件下模型HO - CO混合物的介电常数。我们发现，基于理论的混合规则依赖于系统地结合纯流体的摩尔极化率，会系统性地高估混合物的介电常数，这对于非极性和强极性组分的混合物来说是可以预期的。在我们研究的较低压力下，常用的基于洛伊enga的半经验混合规则对该系统适用，但在较高压力和密度下会略微低估介电常数，尤其是在组成范围的富水端。
