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Molecular dynamics simulations for CO2 absorption spectra. I. Line broadening and the far wing of the v3 infrared band

Classical molecular dynamics simulations (CMDS) have been carried out for gaseous CO2 starting from the intermolecular potential energy surface. Through calculations for a large number of molecules treated as rigid rotors, various autocorrelation functions (ACFs) are obtained together with probabilities of rotational changes. Those used in the present paper are the ACFs of the center of mass velocity and of the molecular orientation, and the conditional probability of a change of the angular speed. They enable calculations, respectively, of the mass diffusion coefficient, of the infrared (dipolar) band shape including the wings, and of individual line-broadening coefficients. It is shown that these calculations, free of any adjustable parameter, lead to good agreement with measured values. This is expected from previous studies for the mass diffusion coefficient and line-broadening coefficients, but it is, to our knowledge, the first demonstration of the interest of CMDS for the prediction of band wings. The present results thus open promising perspectives for the theoretical treatment of the difficult problem of far wings profiles. © 2010 American Institute of Physics.

 Hartmann J.-M., Boulet C., Tran H., Nguyen M.T.
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  Từ khóa : Adjustable parameters; Angular speed; Autocorrelation functions; Band shapes; Broadening coefficients; Center of mass; Classical molecular dynamics; Conditional probabilities; Infrared bands; Intermolecular potential energy surfaces; Line broadening; Mass diffusion coefficients; Molecular dynamics simulations; Theoretical treatments; Diffusion in solids; Molecular orientation; Probability; Quantum chemistry; Regression analysis; Rigid rotors; Molecular dynamics