Computation of elastic and dynamic properties of the liquid phase of noble metals illustrating typically for molten Ag and Cu

Abstract

The potential function as formulated by Bretonnet and Deroache is applied to liquid Cu and Ag to derive longitudinal and transverse phonon frequencies, the power spectrum, and the velocity autocorrelation function. From these phonon frequencies the elastic constants are evaluated. They are also calculated with the help of Schofield's equations which are computed through the first and second derivatives of the potential energy. The values are found to be in satisfactory agreement with each other. The ratio of the areas in negative regions of the velocity correlation function for these f.c.c. packed liquids are found to be equal to the ratio of their atomic weights. The characteristic frequencies calculated by several methods are in satisfactory agreement with each other. The nearest-neighbour distance obtained by different methods is also given. It is observed that the ω_L (k) maximum occurs around k_F, the Fermi wave vector. From the velocity of sound calculated from the experimental compressibility and k_F the ω_L (k) maximum is computed and is found to be in reasonable agreement with other values.