Liquid-vapor isotopic fractionation factors of diatomic fluids: A direct comparison between molecular simulation and experiment

摘要

Liquid-vapor fractionation factors of molecular fluids are studied by molecular-based simulation,Gibbs ensemble Monte Carlo,and isothermal-isochoric molecular dynamics of realistic models for N_2,O_2,and CO.The temperature dependence of the fractionation factors for ~(15)N~(14)N/~(14)N_2,~(15)N_2/~(14)N_2,~(18)O~(16)O/~(16)O_2,~(18)O_2/~(16)O_2,~(13)C~(16)O/~(12)C~(16)O,and ~(12)C~(18)O/~(12)C~(16)O along the vapor-liquid coexistence curves as predicted by simulation is compared with the existing experimental data to assess the accuracy of h~2-order Kirkwood-Wigner free energy expansion for specific model parametrizations.Predictions of the fractionation factors for other isotopologue pairs,including ~(18)O~(17)O/~(16)O_2,~(16)O~(17)O/~(16)O_2,and ~(17)O_2/~(16)O_2,as well as tests of some approximations behind the microscopic interpretation of the fractionation factors are also given.