Many Body Interaction in Alkali Halides

Abstract

The effect of the many body interaction proposed by Sarkar and Sengupta is considered in detail. The method of homogeneous deformation is extended to include many body interactions in which the potential depends on several scaler distances. The general expressions for the elastic constants obtained by this method are compared with those obtained from the long wave theory. Including the various central interactions the model is applied t o calculate the elastic constants, the cohesive energy, and the phase transition pressure for the six halides of potassium and rubidium. It is found that the inclusion of the three body interaction considerably improves the agreement.Der Effekt der Vielteilchenwechselwirkung, auf den von Sarkar und Sengupta hingewiesen wurde, wird im Einzelnen betrachtet. Die Methode homogener Deformation wird erweitert unter Einbeziehung der Vielteilchenwechselwirkung, bei der das Potential von einigen MaBstabslangen abhangt. Die allgemeinen Ausdrucke fur die elastischen Konstanten, die nach dieser Methode erhalten werden, werden mit den nach der Langwellentheorie erhaltenen Werten verglichen. Unter EinschluB der verschiedenen Zentralwechselwirkungen wird das Model1 verwendet, um die elastischen Konstanten, die Kohasionsenergie und den Phasenubergangsdruck fiir die sechs Halogenide des Kalium und des Rubidium zu berechnen. Die Berucksichtigung der Dreikorperwechselwirkung verbessert die Ubereinstimmung betrachtlich.

Two‐ and Three‐Body Interactions and Phonons in Some F.C.C. Metals

“…By three-body interaction here we mean an extra interaction energy owing to the presence of the third particle. This type of interaction may occur through the deformation of the electron shells [9]. The three-body interaction considered here is central in nature in the sense that i t depends on the scalar distances between the particles,…”

Higher‐Order Elastic Constants and Thermoelastic Properties of Ionic Solids

“…[71].Paul was able to predict the breakdown of only one Cauchy relation for TOEC, viz. C, , = C,,,.On the other hand, the inclusion of Lundqvist's three-body potential [11] derived from Lowdin's quantum mechanical treatment [ 101 predicts correctly the breakdown of all the Cauchy relations (15).Using Lundqvist's energy expression Puri and Verma[49] calculated the TOEC of NaCl and KC1.…”