Correlation Effects in Atomic Thermal Vibration of fcc Crystals

Abstract

Analytical expression for the Displacement-displacement Correlation Function (DCF) CR has been derived based on the derived Mean Square Relative Displacement (MSRD) σ2 and the Mean Square Displacement (MSD) u2 for fcc crystals. The effective interaction potential of the system has been considered by taking into account the influences of nearest atomic neighbors, and it contains the Morse potential characterizing the interaction of each pair of atoms. Numerical calculations have been carried out for u2 , σ2 and CR functions of Cu and Ni. The ratio CR /u2 is 40% and CR / σ2 25% at high temperatures. They are found to be in good agreement with experiment and with those calculated by the Debye model.