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Dispersion curves for the polyglycine I chain are calculated for both the in-plane and out-of-plane modes of vibration, and the force constants are fitted by comparison with observed infrared frequencies. Frequency distributions for polyglycine I and polyglycine II are calculated from inelastic neutron scattering. The intensity difference of the C–N torsional band between polyglycine I and polyglycine II suggests the presence of additional C–H···O-type hydrogen bonding between chains in the helical (II) form. An estimate of the sum of conformational and lattice energy difference in the two forms is made.

The scattering of low-energy neutrons (0.005 eV) has been used to study translational and librational motions of H2O molecules in various configurations in crystals in a frequency region lying below 1000 cm−1. An attempt is made in this paper to determine the effects of various cations and anions on the frequencies of intermolecular motions of H2O molecules in crystalline salts. The neutron spectra were obtained for a series of hydrates in which the H2O is hydrogen bonded to the same anion, Cl−, but on the sphere of coordination of different cations (Al3+, Cr3+, Sr2+, Ca2+, Fe2+, Mg2+, Co2+, Ni2+) and for Al salts with different anions (NO3−, SO42−, Cl−). This investigation tends to suggest that the vibrational frequencies of the H2O molecules are strongly dependent upon the degree and strength of coordination of the molecule as well as upon the degree and strength of the hydrogen bonds formed with neighboring anions or H2O molecules.

A simple method of relating the scattered neutron energy distribution to the molecular frequency spectrum in hydrogenous solids is given. The method is approximate because of the neglect of translation-rotation couplings, but should be of practical interest for systems where translational and librational frequencies do not appreciably overlap. The approach is applied to cold-neutron-scattering data from hexagonal ice at 150°K. The resulting thermodynamic frequency distribution is used to compute moments, specific heat, and root-mean-square amplitude of vibrations. Comparison is made with optical, thermodynamic, x-ray, and neutron measurements.