Spectral Analysis of the Velocity Autocorrelation Function of a Model Liquid

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Abstract
Studies are made on a spectral analysis of the velocity autocorrelation function (VAF) obtained by computer simulation by using the method of molecular dynamics. Oscillating bumps are observed in the power spectra by direct cosine transforms of the long data of VAF. To investigate the source of bump, the behaviour of the tail of VAF is studied in detail. This investigation proves that the bumps are raised by the lack of a damping factor of the tail. The unreliable structure is weeded out from the spectrum by applying one of the methods of the spectral analysis of time series, the maximum entropy method, to our system. A strong damping is found in the tail of VAF predicted by the maximum entropy extention.