tailieunhanh - Development of new cross intermolecular pair potential ab initio and prediction of cross second virial coefficients for dimer H2O-CH4

The site-site intermolecular pair potential of dimer H2O-CH4 was constructed from the ab initio calculations at high level of theory CCSD(T) with basis set cc-pVTZ. The cross second virial coefficients of this system were calculated accurately using this ab initio pair potential. These results were compared with experimental data and those from literatures. The discrepancies between them are insignificant. | Journal of Chemistry, Vol. 47 (6), P. 786 - 790, 2009 DEVELOPMENT OF NEW CROSS INTERMOLECULAR PAIR POTENTIAL AB INITIO AND PREDICTION OF CROSS SECOND VIRIAL COEFFICIENTS FOR DIMER H2O-CH4 Received 2 May 2008 PHAM VAN TAT Department of Chemistry, University of Dalat Abstract The site-site intermolecular pair potential of dimer H2O-CH4 was constructed from the ab initio calculations at high level of theory CCSD(T) with basis set cc-pVTZ. The cross second virial coefficients of this system were calculated accurately using this ab initio pair potential. These results were compared with experimental data and those from literatures. The discrepancies between them are insignificant. Keywords: cross intermolecular pair potential, cross second virial, ab initio potential. I - INTRODUCTION The thermodynamic data needed for designing processes of gaseous fuels in several industrial applications. The methods for predicting the physical properties of the natural gas mixtures are need that can be used with the great significance for a wide range of temperatures, pressures and compositions. The empirical methods are also useful for correlation of quantities of data on specific components. But these were not generated the properties of new components accurately. In recent years computer simulations have become indispensable tools for studying fluids and fluid mixtures. One of the first attempts Nasrabad and Deiters predicted phase high-pressure vaporliquid phase equilibria of noble-gas mixtures [1,2] from the global Monte Carlo simulations using the intermolecular potential ab initio. These simulations are to predict the thermodynamic properties of microscopic systems using the intermolecular potentials, and we can be understood macroscopic behaviours 786 [3]. The reliability of these depends only on the accuracy of intermolecular potentials. In this work we report the development of an accurate cross potential ab initio between molecules water and methane using the high level