GROWTH AND COLLAPSE OF STRUCTURAL PATTERNS IN THE HYDROGEN-BOND NETWORK IN LIQUID WATER

Intermittent and chaotic motions of the hydrogen bond network are stud ied with the molecular dynamics (MD) simulation. By analyzing the fluc tuation in the radial distribution function, it is shown that individu al water molecule alternately goes through two different periods; the structured period during which the local structure around the molecule is developed more than the average and the destructured period during which the local structure is less developed. At room temperature the lifetime of each period is hierarchically distributed from a few hundr eds fsecs to several psecs. This intermittent structural fluctuation i s quantitatively analyzed by defining a new quantity, local structure index (LSI). Molecules which have the large LSI value have tendency to be close to each other to form clusters. Temporal and spatial correla tions of the structural order are studied with this new method. The an alyses of the structural fluctuation provide a new perspective to stud y the collective motion of water molecules. (C) 1996 American Institut e of Physics.