A molecular theory for the thermodynamic behavior of polar mixtures. I. The statistical-mechanical local-composition model

Molecular dynamics simulations have been performed for methanol/carbon tetrachloride mixtures over the whole composition range at 323 K and zero pressure. The OPLS ͑optimized potentials for liquid simulation͒ potential energy parameters by Jorgensen were used to model the methanol potential. Both a non-polarizable carbon tetrachloride model taken from McDonald, Bounds, and Klein ͓Mol. Phys. 45, 521 ͑1982͔͒ as well as a polarizable model were used. The latter model was devised by combining the model of McDonald, Bounds, and Klein with the atomic polarizabilities proposed by Applequist, Carl, and Fung ͓J. Am. Chem. Soc. 94, 2952 ͑1972͔͒. We show that the role of the methanol-carbon tetrachloride interactions are very important in discussing the thermodynamic mixing properties. In order to reproduce the asymmetric behavior of the excess enthalpies with respect to composition it is necessary to include the non-additive polarization interaction. The structure and especially hydrogen bonding properties are discussed. Radial distribution functions show a strong tendency of methanol to preserve the local order similar to the one in the pure fluid. The deviations from random mixing are more pronounced at the lower mole fractions. This is explained by a frustration model. At low methanol concentrations the molecules get more freedom to align themselves in energetically favorable ͑hydrogen bonded͒ configurations. Throughout the composition range, the majority of the methanol molecules is found to be engaged in two hydrogen bond, As in the pure fluid, this leads to the pattern of hydrogen bonded winding chains. Upon dilution the degree of cross-linking between the chains diminishes whereas the free monomer fraction rises. Furthermore a significant number of the remaining chains close to form cyclic polymers.

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“…26 The local mole fraction x i j loc (L) of the i component around a reference molecule of component j is given by…”

Section: Structural Propertiesmentioning

confidence: 99%

Molecular dynamics study of the thermodynamic and structural properties of methanol and polarizable/non-polarizable carbon tetrachloride mixtures

Veldhuizen

Leeuw

1996

The Journal of Chemical Physics

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“…In the following, efforts are made to express the excess Gibbs free en- ergy in terms of molecular interactions among species in the system (and composition and temperature). This is achieved by following closely the approached developed in the generalized van der Waals (GVDW) theory [12,[16][17][18][19][20][21][22]. (Note that conventionally, the one-fluid lattice theory [23] and/or the two-fluid theory [13,24] are used to obtain the expression for G ex .…”

Section: The Fundamentals Of a Proper Local Composition Model At Consmentioning

confidence: 99%

Towards the development of theoretically correct liquid activity coefficient models

Lin¹,

Hsieh²,

Hsieh³

et al. 2009

The Journal of Chemical Thermodynamics

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“…Another route, known as the generalized van der Waals (GVDW) theory [16][17][18][19][20][21][22], is focused on the formulation of a generalized partition function, from which both the EOS and activity coefficient equations can be derived. It has been shown [20] that, under different approximations, most of the commonly used EOS and activity coefficient model can be derived from a single generalized van der Waals partition function.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic equations of state from molecular solvation

Lin¹

2006

Fluid Phase Equilibria

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A molecular theory for the thermodynamic behavior of polar mixtures. I. The statistical-mechanical local-composition model

Cited by 41 publications

References 27 publications

Molecular dynamics study of the thermodynamic and structural properties of methanol and polarizable/non-polarizable carbon tetrachloride mixtures

Molecular dynamics study of the thermodynamic and structural properties of methanol and polarizable/non-polarizable carbon tetrachloride mixtures

Towards the development of theoretically correct liquid activity coefficient models

Thermodynamic equations of state from molecular solvation

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