Lattice vibrations of sodium chloride: Experimental and theoretical heat capacity data

Vibrational frequency spectra of sodium chloride derived from two theoretical models which allow for ionic deformability, instead of treating the ions as rigid point charges, have been used to calculate effective Debye temperatures and distribution function moments. The results are compared with those deduced from specific heat measurements. For the second, more refined, model the agreement with experiment is considerably better than that achieved when the ions are treated as rigid point charges as in the simple Born theory.