Thermodynamic functions of liquid water calculated from the temperature evolution of the vibration spectrum contour

Configurational contributions of hydrogen bonds to thermodynamic properties of water (internal energy, entropy, and heat capacity) are calculated on the basis of statistical distributions of frequencies of the OH vibrations of liquid water, calculated earlier from the experimental Raman spectra in frameworks of the fluctuation theory of hydrogen bonding. Distributions of the energy of hydrogen bonds are determined. It is shown by comparison with computer experiments that previously established dependence of energy on frequency, E(ν), must be considered in this formalism as the effective energy of hydrogen bonding averaged over those configurations of hydrogen bridge O-H···O which lead to the given frequency ν in the vibrational spectrum. Contribution of van der Waals interactions not affecting the frequency shift to heat capacity is evaluated.