The Study of Vander Waals (vdW) Coefficients for Chalcogenide Semiconductor Compound (ChSCs)

Abstract

The vdW equation is an equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion and r-6 vdW attraction). The vdW force (or vdW interaction), named after Dutch Scientist Johannes Diderik van der Waals, is the attractive or repulsive force between the molecules (or between parts of the same molecule) other than those due to the covalent bonds or the electrostatic interaction of ions with one another or with neutral molecules. The investigation of physical properties of the crystals depends on the motion of the constituent atoms (or ions) and requires the knowledge of actual form of the phonon frequency spectrum, which can be achieved from the theoretical models of lattice dynamics. The efforts have been made to develop a series of lattice dynamical models, which have progressed rapidly through the simple phenomenological to the sophisticated microscopic approaches. The energy is written as a function of a single lattice constant and the structure has been determined by minimizing the energy with respect to this parameter. These are the total electron density which is the sum of the two separate densities and the non Coloumbic part of the interaction potential may be evaluated by an electron gas treatment. It has been found that the vdW interactions are quite important in the calculation of cohesive energies of different crystal structures [10]. The prediction of relative stability and phase transition depends appreciably on the accuracy of determining the vdW coefficients (ckk? and dkk? ). In this study evaluation of The Study of Vander Waals (vdW) coefficients for Chalcogenide Semiconductor compound (ChSCs) is been made and result is recorded which can be used as reference for many future studies. In the present study of mixed Chalcogenide semiconductor Compounds (ChSCs). We have used the Hafemeister and Flygare (HF) type potential which allows us to extend the overlap repulsion up to second neighbour ions. In the present study the values of and c//A- obtained from SKV approach have been used for the evaluation of vdW energies.