AUTOCORRELATION FUNCTIONS OF TRANSLATIONAL AND ROTATIONAL VELOCITIES IN MOLECULAR DYNAMIC MODELS OF WATER AND THEIR SPECTRA

Autocorrelation functions of the velocity of the center of mass of water molecules, translational velocity of hydrogen atoms in these molecules, and rotational velocity of the entire molecule are calculated by molecular dynamics. The spectra of these functions are obtained. The effect of temperature and pressure on these spectra is studied. It is established that the spectra reflect in detail the features of all types of motion: they clearly show the correlation between the rotation of the molecule and its motion and can well distinguish between individual molecular motions in the cage of the nearest neighbors and their participation in collective motions of different scales.