Direct method for MD simulations of collision-induced absorption: Application to an Ar–Xe gas mixture

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With the reformulation of the classical equations of collision-induced absorption, we present a method to perform the direct computation of the spectral density function. This way the absorption coefficient can be computed from classical molecular dynamics (MD) without the computationally demanding evaluation of the dipole autocorrelation function. In addition, we have developed an algorithm to extract the bound-to-bound dimer contribution to the MD simulated absorption. The method has been tested on the Ar–Xe rare gas system. Comparisons with quantum mechanical (QM) and conventional MD methods validate the approach. The obtained MD bound-to-bound spectra generally agree in shape and magnitude with QM results, including features stemming from rotations and vibrations of the Ar–Xe dimer.