Tetrahedral Ordering in Water: Raman Profiles and Their Temperature Dependence

The supramolecular organization of liquid water is discussed in connection with both the spectral profile of the OH stretching Raman signal measured in pure water and the distribution of tetrahedral order computed by molecular dynamics simulations. Both curves show common features and a similar temperature dependence never pointed out before. Energetic information extracted from the Raman profiles using a recently proposed integration method is also discussed. Overall results confirm that thermally induced structural variations of water in the interval of temperature ranging from 10 to 75 degrees C involve a change of the local tetrahedral order associated with a redistribution energy of 1.6-1.7 kcal/mol.