Phase Equilibria by Molecular Mechanics

  • Jonsdottir, Svava Osk (Project Manager)
  • Rasmussen, Kjeld (Project Participant)
  • Rasmussen, Peter (Project Participant)
  • Klein, Roger A. (Project Participant)

Project Details


A method for predicting interaction parameters used in phase equilibrium calculations has been developed, in which molecular mechanics calculations of the interaction energies between pairs of molecules in the solution of interest is carried out. The method has been used to calculate the vapor-liquid equilibrium for non-polar as well as polar organic solutions with and without hydrogen bonds, and for polymer solutions. The method has also been extended to predict solid-liquid equilibria of carbohydrates in aqueous solution. The interaction energy is calculated as the difference between the potential energy of a pair of molecules isolated in space and the potential energies of the individual molecules. Three such interaction energies must be determined in order to calculate at pair of interaction parameters for a binary mixture; one between unlike molecules and two between like molecules. Two molecules can be oriented in many different ways relative to each other, and several conformers of each molecule may also be possible. Sampling the conformational space of two isolated molecules in a reasonable manner is therefore a complex problem. It is carried out as a Monte Carlo search combined with energy minimization. A molecular mechanics description of the system consists of a series of inter-atomic potentials for non-bonded interactions, as well as internal degrees of freedom. We have found that it is possible to study inter-molecular interactions on a microscopic scale, and to use these results in order to gain insight into the behavior on a macroscopic scale.
Effective start/end date01/03/199731/12/2000

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