Harmonic vibrations hydrogen bond dipoles

Section VI. It is possible to unblock the first drawback (i), if to assume a nonrigidity of a dipole—that is, to propose a polarization model of water. This generalization roughly takes into account specific interactions in water, which govern hydrogen-bond vibrations. The latter determine the absorption R-band in the vicinity of 200 cm-1. A simple modification of the hat-curved model is described, in which a dipole moment of a water molecule is represented as a sum of the constant (p) and of a small quasi-harmonic time-varying part p(/j. 

C. Harmonic Vibration of Dipoles along and about a Hydrogen Bond... 

ABSTRACT Ground state properties of several conceivable hydrogen bonded trimers composed of HCN and HP molecules have been evaluated at the SCP level. The most stable ones of these trimeric complexes have subsequently been reinvestigated with electron correlation methods (ACPP). We provide a survey of stabilization energies, dipole moments, selected harmonic vibrational frequencies and corresponding infrared intensities. We also discuss various aspects of the non-additivity of intermolecular interaction taking place in these clusters. 

The discussion in the last two paragraphs is slightly over-simplified, since, if the vibrations are simple harmonic and the dipole moment a linear function of inter-nuclear distance, the mean dipole moment is independent of the amplitude. The differences which actually occur are due partly to anharmonicity, which is particularly marked in bonds involving hydrogen, and partly to a non-linear variation of dipole moment with internuclear distance, sometimes called electrical anharmonicity. 

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