Phonon Dispersion Curves of Silver (Ag) and Gold (Au): Application of Density Functional Theory and Inter – Atomic Force Constant
Abstract
The Computational theoretical techniques using first principle which make use of the density functional theory as implemented by quantum expresso as well as inter – atomic force constant (IFC) techniques (Born-von Jarman) were used to investigate the phonon dispersion curves of Silver (Ag) and Gold (Au)
The results obtained show that for Au, the extension to 1 – 6th neighbour gave slightly close agreement with the experimental phonon dispersions when compared to the 1 – 5th neighbor at WT and LL symmetry points. The percentage error for Au at WT are 2.5% and 2.9% ; at point LL we obtained 0.6% and 0.7% respectively. The Local density Approximation (LDA) results for Ag underestimates the lattice with about 1.6% while the Generalized Gradient Approximation (GGA) overestimates it by 1.9%.