In Band Absorption of Monovalent Impurities in Sodium Chloride

Abstract

In this paper preliminary results of an investigation of the far infrared absorption spectrum of sodium chloride containing monovalent impurities are reported. in recent thermal conductivity measurements on this system Caldwell and Klein (1) observed depressions of the thermal conductivity curves which were asymmetrical with respect to the peak and interpreted their results in terms of scattering of phonons by lattice resonant modes associated with the impurities. A shell model was used to describe the phonons of the perfect lattice and a simple model of the impure lattice was assumed. This involved a change of mass at the defect site together with a change of central force constant to the six nearest neighbors. This model was only moderately successful in predicting the shape of the thermal conductivity curves and the present work was undertaken in order to obtain more detailed information about the resonance modes responsible for the thermal conductivity depressions.

This work was supported by the Advanced Research Projects Agency under Contract SD-131.