Thermodynamic properties of mixtures of Kihara molecular fluids from perturbation theory

Abstract

A perturbation theory for mixtures of molecules interacting through the Kihara potential is proposed. We show that the Kihara potential with the Lorentz-Berthelot combination rule to describe the crossed interaction is able to give very good results for the excess properties of different mixtures. The results obtained by using the Kihara model are comparable to or even better than those obtained with the more popular site-site model. We have applied the theory to several mixtures of hydrocarbons involving different geometries, such as methane + ethane, methane + propane, ethane + propane, methane + isobutane, ethane + isobutane, and propane + benzene. In all the cases the calculated excess properties agree very well with the experimental values. The theory can be applied to any nonpolar mixture without restriction of geometry and the calculations can be performed in a personal computer which make the theory well suited for practical applications.

Orthobaric volumetric properties of liquid (propane + cyclopropane) betweenT= (158 and 201) K

“…In the temperature range studied, the excess molar volume of (propane + cyclopropane) decreases with temperature. The values determined for the mixtures with x(C 3 H 8 ) = 0.5 (5) at three temperatures T were V E m (x = 0.5) = 0.17 cm 3 · mol −1 at T = 165 K, V E m (x = 0.5) = 0.14 cm 3 · mol −1 at T = 175 K, and V E m (x = 0.5) = 0.13 cm 3 · mol −1 at T = 185 K. The estimated precision for the excess molar volumes is ±0.02 cm 3 · mol −1 .…”

“…The parameters obtained are listed in table 6. Figure 4 shows the curve for the excess molar volume of (propane + cyclopropane) at T = 175 K predicted by the Deiters equation of state {calculated value of V E m (x = 0.5, T = 175 K) = 0.24 cm 3 · mol −1 } together with the present experimental values {V E m (x = 0.5, T = 175 K) = 0.14 cm 3 · mol −1 }. The equation of state yields the correct sign and order of magnitude of the excess molar volume.…”

“…However, as far as the liquid structure is concerned, they constitute useful model molecules since they can be well described by simple intermolecular potentials. (2,3) The present work, which reports precise measurements of the volumetric properties of mixtures of a linear and a cyclic molecule (propane and cyclopropane), is a contribution to a better understanding of the properties of mixtures involving small cyclic molecules. Furthermore, the deviations from ideality shown by the mixtures studied make them a good test system for statistical theories of liquids.…”

Теплота Плавления Малых Кластеров В Модели Потенциала С Эффективной Глубиной Потенциальной Ямы

“…В первом приближении размерные зависимости для теплоты плавления и температуры плавления для на-нокластеров должны совпадать по функциональному виду [23]. Это подтверждается в рамках приближения " скин-слоя" для размерного эффекта, в котором за-висимость теплоты плавления от размеров кластера определяется формулой [24] ( * ) П р и м е ч а н и е. Третья строка в разделе потенциал Леннард-Джонса относится к параметрам потенциала Морзе [27], для бензола -вторая строка к параметрам потенциала Кихары [29].…”

“…Для органических жидкостей применение потенциала Леннард-Джонса не совсем корректно, поэтому для бензола были взяты кроме параметров этого потенциала значение параметров потенциала Кихары [29], тогда H m (13)/ε Kich. = 1.16 в единицах глубины потенциаль-ной ямы потенциала Кихары.…”