Theory and efficient computation of differential vibrational spectra

We developed a general computational scheme for differential spectra on the basis of time correlation function and perturbation theory. The scheme provides a quite efficient route to evaluate small differential spectra by molecular dynamics simulation instead of the straightforward subtraction of two spectra. Applications of this scheme have demonstrated that the proposed route is accurate and far more efficient in several orders of magnitude. The present method enables us to analyze a variety of experimental differential spectra using molecular dynamics simulation.