Pressure dependent study of phase transition and elastic constant of KCl and KBr

A theoretical study of phase transition and various elastic constant using two body interaction model is carried out. The calculated values of phase transition pressure and the vast volume discontinuity in pressure–volume (PV) phase diagram indicate the structural phase transition from rock salt (B1) to zinc blend (B2) structure of potassium chloride (KCl) and Potassium Bromide (KBr). Fair agreement with lattice theoretical data calculated from an interaction potential model composed of Coulomb force, van der Walls force and first and second nearest neighbor repulsive forces is found. The present calculation have revealed good agreement with the available experimental data on the phase transition pressures (5 and 10 GPa). On the basis of Born’s stability criteria the relations between the pressure dependence of the bulk modulus (BT), shear moduli (C44) and tetragonal moduli (CS) to the B1-B2 transition are also investigated.