CRCU

Chemical Research in Chinese Universities ›› 2001, Vol. 17 ›› Issue (4): 432-438.

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A Thermodynamic Model for Square-well Chain Fluid: Theory and Monte Carlo Simulation

ZHANG Bing-jian1, LU Ying-hong1, HU Wen-xuan2, JIN Zhi-jun3   

  1. 1. Department of Chemistry, Zhejiang University, Hangzhou 310027, P.R. China;
    2. Department of Earth Sciences, Nanjing University, Nanjing 210093, P.R. China;
    3. Basin and Reservoir Research Center, China Petroleum University, Beijing 102200, P. R. China
  • Received:2000-08-16 Online:2001-12-24 Published:2011-08-04
  • Supported by:

    Supported by the National Major Fundamental Research and Development Project (No.G19990433), and by National Natural Science Foundation of China(No.29977018).

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Abstract: A thermodynamic model for the freely jointed square-well chain fluids was developed based on the thermodynamic perturbation theory of Barker-Henderson, Zhang and Wertheim.In this derivation Zhang's expressions for square-well monomers improved from Barker-Henderson compressibility approximation were adopted as the reference fluid, and Wertheim's polymerization method was used to obtain the free energy term due to the bond connectivity.An analytic expression for the Helmholtz free energy of the square-well chain fluids was obtained.The expression without adjustable parameters leads to the thermodynamic consistent predictions of the compressibility factors, residual internal energy and constant-volume heat capacity for dimer,4-mer, 8-mer and 16-mer square-well fluids.The results are in good agreement with the Monte Carlo simulation.To obtain the MC data of residual internal energy and the constant-volume heat capacity needed, NVT MC simulations were performed for these square-well chain fluids.

Key words: Square-well chain, Perturbation theory, Compressibility factor, Internal energy