The effect of pressure on hydrogen bonding in water: IR study of nu(OD) HDO at pressures of up to 1500 bar

A seeming contradiction has been revealed between the behaviour of the shor test intermolecular separation r(00) and that of the frequency of the OH vi bration of H2O under compression in liquid water. Decrease of r(00) with in creasing pressure up to 2 kbar seems to be evidence of strengthening of the hydrogen bonding, but the increase in the frequency of v(OH) H2O seems con tradictory. To clear up this question, measurements of the integrated inten sity of IR absorption for v(OD) HDO have been made which definitely show th at the energy of the hydrogen bonds decreases under compression at least up to 1.5 kbar. The decrease in the intensity is of about 20%, i.e., essentia lly more than the estimated accuracy of the measurements. Monte Carlo simul ations of the compression of liquid water show that the behaviour of r(00), v(OH), and the integrated intensity can be explained by the bending of hyd rogen bonds.