An analysis of electronic polarizabilities of ions in alkali halides has been performed by making use of the Wilson–Curtis–Coker model for describing the variation of polarizabilities in going from free state to a bonded state. More accurate values of free state polarizabilities for anions have been obtained making use of photoelastic data. These polarizabilities are found to be larger than Pauling’s values but smaller than Coker’s values. The free state polarizabilities obtained in the present work are then used to estimate the molecular state polarizabilities for 20 alkali halides. The dipole moments and their derivatives with respect to internuclear distances are then calculated and compared with experimental data in order to make a critical test of the polarizability data.

Crystals of cuprous halides, silver halides, and thallous halides are found t o show significantly different behaviour from that of alkali halides. This difference is mainly due to the presence of outermost d-electrons present in Cu+, Agf, and T1+ ions. I n t,he present paper an analytical potential form is used for the overlap repulsive energy derived by Harrison from quantum mechanical considerations. The parameters in this potential form have direct correlation with the valence state energies for outermost d-electrons. The potential model is applied to calculate the cohesive energies, pressure derivatives of bulk modulus, Griineisen parameter and its volume dependence using different existing theories. ES

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The interionic potential model recently developed by taking account of the composite effect of short range repulsive and dispersion forces along with three body interactions is extended in the present work to calculate the (i) third and fourth order elastic constants, (ii) first and second order pressure derivatives of second order elastic constants, (iii) photoelastic constants, volume derivatives of dielectric constants, and optic mode Griineisen parameters. The calculated values of various physical quantities are found to present close agreement with experimental data.Das kurzlich unter Berucksichtigung des Einflusses der Zusammensetzung auf die kurzreichweitigen AbstoBungs-und Dispersionskriifte entwickelte Interionenpotentialmodell wird zusammen mit Dreikorperwechselwirkungen erweitert und 1. die elastischen Konstanten dritter und vierter Ordnung, 2. die Druckableitungen erster und zweiter Ordnung der elastischen Konstanten zweiter Ordnung, 3. die photoelastischen Konstanten, Volumenableitungen der Dielektrizitatskonstanten und die Gruneisenparameter der optischen Mode berechnet. Die berechneten Werte der verschiedenen physikalischen GroBen ergeben enge ubereinstimmung mit den experimentellen Werten.

The potential-energy derivatives are derived directly from the experimental values of the spectroscopic constants for diatomic alkali halides. It is found that these derivatives are useful in predicting more accurately the values of the higher order spectroscopic constant (βe). Some interesting new relations showing the dependence of the potential-energy derivatives on internuclear distances have been investigated empirically. An attempt has been made to interpret these relations on the basis of interionic potentials.