Propagation of sound in water. A molecular-dynamics study

Fluctuation phenomena occurring in a system of 216 water molecules, studied by molecular dynamics at 1 g cm^-3 and 10 ^, indicate that (i) transverse currents persist in the form of propagating collective coordinates even for a wavelength of about 20, with indications that the same will happen for much longer wavelengths. The velocity of propagation is 1. 05 10^5 cm sec^-1. In the region of 20 the lifetime of the fluctuation appears to increase linearly with increasing wavelength. (ii) Density fluctuations at 20 are found to be propagating but only marginally; the corresponding velocity of sound is 1. 8 10^5 cm sec^-1. (iii) The spectrum of density fluctuations exhibits a secondary maximum at a much higher frequency than the normal frequency of sound propagation and it is suggested that experiments should be directed to the region of this "high-frequency sound. "