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Barlette Vania Elisabeth Garbujo Fábio Luiz Laurenti Freitas Luiz Carlos Gomide 《Molecular Engineering》1997,7(3-4):439-455
A five site potential model combining Lennard–Jones plus Coulomb potential functions has been developed for chloroform molecule.
The partial charges needed for Coulombic interactions were derived using the chelpg procedure implemented in the gaussian
92 program. These calculations were performed at the MP2 level with MC-311G* basis set for Cl and 6-311G** for C and H atoms.
The parameters for the Lennard–Jones potentials were optimized to reproduce experimental values for the density and enthalpy
of vaporization of the pure liquid at 298 K and 1 atm. The statistical mechanics calculations were performed with the Monte
Carlo method in the isothermic and isobaric (NpT) ensemble. Besides the values obtained for density, ρ, and molar enthalpy
of vaporization at constant pressure, Δ HV, for liquid chloroform, results for molar volume, Vm, molar heat capacity, Cp, isobaric thermal expansivity, αp, and isothermal compressibility, κT, for this pure liquid are also in very good agreement with experimental observations. Size effects on the values of thermodynamic
properties were investigated. The potential model was also tested by computing the free energy for solvating one chloroform
molecule into its own liquid at 298 K using a statistical perturbation approach. The result obtained compares well with the
experimental value. Site–site pair correlation functions were calculated and are in good accordance with theoretical results
available in the literature. Dipole–dipole correlation functions for the present five site model were also calculated at different
carbon–carbon distances. These correlations were compared to those obtained using the four site model reported in the literature.
An investigation of the solvent dependence of the relative free energy for cis/trans conversion of a hypothetical solute in
TIP4P water and chloroform was accomplished. The results show strong interaction of water and chloroform molecules with the
gauche conformer. The value obtained for the free energy barrier for cis/trans rotation in TIP4P water is higher than that
for chloroform. This result is in agreement with the continuous theory for solvation as the conformer with higher dipole moment
is more favoured by the solvent with higher dieletric constant. The results also show an increase in entropy as the solute
goes from the cis to the trans geometry and this result is more appreciable in the aqueous solution.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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