Your browser doesn't support javascript.
loading
Chemical potentials and phase equilibria of Lennard-Jones mixtures: a self-consistent integral equation approach.
Wilson, D Scott; Lee, Lloyd L.
Afiliação
  • Wilson DS; School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma 73072, USA.
J Chem Phys ; 123(4): 044512, 2005 Jul 22.
Article em En | MEDLINE | ID: mdl-16095374
We explore the vapor-liquid phase behavior of binary mixtures of Lennard-Jones-type molecules where one component is supercritical, given the system temperature. We apply the self-consistency approach to the Ornstein-Zernike integral equations to obtain the correlation functions. The consistency checks include not only thermodynamic consistencies (pressure consistency and Gibbs-Duhem consistency), but also pointwise consistencies, such as the zero-separation theorems on the cavity functions. The consistencies are enforced via the bridge functions in the closure which contain adjustable parameters. The full solution requires the values of not only the monomer chemical potentials, but also the dimer chemical potentials present in the zero-separation theorems. These are evaluated by the direct chemical-potential formula [L. L. Lee, J. Chem. Phys. 97, 8606 (1992)] that does not require temperature nor density integration. In order to assess the integral equation accuracy, molecular-dynamics simulations are carried out alongside the states studied. The integral equation results compare well with simulation data. In phase calculations, it is important to have pressure consistency and valid chemical potentials, since the matching of phase boundaries requires the equality of the pressures and chemical potentials of both the liquid and vapor phases. The mixtures studied are methane-type and pentane-type molecules, both characterized by effective Lennard-Jones potentials. Calculations on one isotherm show that the integral equation approach yields valid answers as compared with the experimental data of Sage and Lacey. To study vapor-liquid phase behavior, it is necessary to use consistent theories; any inconsistencies, especially in pressure, will vitiate the phase boundary calculations.
Buscar no Google
Base de dados: MEDLINE Idioma: En Ano de publicação: 2005 Tipo de documento: Article
Buscar no Google
Base de dados: MEDLINE Idioma: En Ano de publicação: 2005 Tipo de documento: Article