ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The theory of molecular liquids based on the extended reference interaction site model (RISM) equation is used to describe the intermolecular structure of a small hydrocarbon chain liquid like n-butane. The model treats the methyl and methylene groups as single interaction centers with pair interactions modeled by a Lennard-Jones (12:6) function and located at the position of the carbon nuclei in the molecule. The theory assumes that the equilibrium internal states distribution of nonpolar flexible molecules are determined primarily by the short range, hard repulsive portions of the intermolecular potential (see preceding paper). The molecular structure factor has been calculated from the theory, and the results are in good agreement with recent x-ray scattering experiments. From this structural information a perturbative scheme to obtain the thermodynamic properties is employed. The theoretical predictions compare favorably with recent simulation results, giving quantitative agreement with the equation state and the intermolecular energy. The effective energy difference between trans and gauche states is obtained from Van't Hoff plots, giving a value of 0.486 kcal/mol. Also, the effective difference of molar volumes between conformers is calculated from ln K vs P plot, obtaining a value of −3.1 cm3/mol, the same order of magnitude than the experimental value observed on liquid 1,2-dichloroethane.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.456491
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