Effect of the hydrogen bridge geometry on the vibrational spectra of water: Two-parameter H-bonding potentials

A principle to design the multi-parameter potentials of hydrogen bonding is proposed and developed. Based on fluctuation theory, they provide the description of temperature evolution of the shape of OH vibrational spectra of liquid water molecules. Approximate solutions expressing the nu(OH) frequency and hydrogen bond energy E through the hydrogen bond length and bending (R (O...O), phi(H-O...O)) and the pair of angles (phi(H-O...O), chi-(O...O)) adjacent to it are found numerically. By their means, spectra are calculated fairly close to experiment in a temperature range up to 200A degrees C. The expressions proposed can be used to quantitatively analyze the networks of hydrogen bonds in computer models of water obtained by Monte-Carlo or molecular dynamics methods.