Orientational relaxation dynamics of water molecules in the liquid state are studied by molecular dynamics with TIP4P model. The biexponential decay of the dipolar autocorrelation function is associated with a heterogeneous distribution of local hydrogen bond patterns. The H-bond pattern was analyzed with a Voronoi polyhedra (VP) construction of the oxygen atom distributions. An asphericity parameter for VP was used to characterize the heterogeneous distribution of the local H-bond patches. The slow relaxation in the ordered region is temperature sensitive. It is associated with locally cooperative rotation around the H-bond axis. The fast (about 1 ps) relaxation, relatively temperature independent, is associated with rototranslational coupling motion of the water molecule in a disordered cage. The origin of the fast rotational relaxation comes from "interstitial molecules" coupling with the center water molecule.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry