Lattice vibrations and infrared absorption of ice Ih

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Abstract
Lattice dynamics calculations have been carried out for ice Ih using the SPC rigid‐molecule effective pair potential whose parameters were fitted to the properties of water. We employ a periodically replicated nonpolar sample of 128 molecules whose constituent molecules are arranged according to the ice rules. Long range dipole–dipole interactions are handled using the Ewald method. The calculated density of states in the translational and librational regions accords well with available experimental data. However, the frequency of the longitudinal optic mode is a little low as is the position of whole librational band. Although polarization (induction) effects are not explicitly included in the calculation of the vibrational frequencies and their associated eigenvectors, they are invoked to evaluate the quantities which determine the infrared absorption, namely, derivatives of the crystal dipole moment with respect to the normal coordinates. The overall features of the infrared spectrum for translational modes are well described by including induction effects due to the molecular dipole and quadrupole fields. The same approach is used to calculate the dielectric constant and the energy loss spectrum. The latter calculations lead to a value of 10 cm−1 for the longitudinal optic–transverse optic mode splitting.