Interpreting Autocorrelation Functions of Translational Motion of Water Molecules in Molecular Dynamics Models

Autocorrelation functions of the velocity of water molecules is interpreted using partial functions characterizing groups of molecules or their velocity components in molecular dynamics simulation models. It is shown that 1) the low frequency maximum at ~40 cm^–1 in the spectrum of autocorrelation functions is caused by the overlap of the spectra of collective vibrations of different scales; 2) the maximum at ~210 cm^–1 is formed by individual vibrations of molecules relative to their immediate environment.