Electronic structure and dynamics analysis of the Cu-Ag binary alloy by a tight-binding parametrization

Abstract Applying the Naval Research Lab tight-binding method, we have developed parameter sets for the Cu-Ag noble metal binary system. The tight-binding Hamiltonians are determined from a fit that has a non-orthogonal basis and reproduces the electronic structure and total energy values of first-principles linearized augmented plane wave calculations. The parameters were fit to the structures B 2 , L 1 0 , L 1 2 ( X 3 Y and Y 3 X ) with the X and Y representing the different combinations of the Cu and Ag in addition to the fcc Cu and Ag. The method reproduced the first-principles ordering of these structures and found the ground-state structure of the system to be the L 1 2 ( Cu 3 Ag ). As an output of this approach, the following quantities were reproduced in good agreement with available experimental and theoretical values: elastic constants, densities of electronic states as well as the total energies of additional crystal structures that were not included in the original first-principles database. We used this TB parametrization to successfully perform molecular dynamics simulations and determined the energies for vacancy formation. Temperature dependence of the coefficient of thermal expansion, the mean squared displacement and phonon spectra for the system were also calculated. In addition we show that these TB parameters work for determining binding energies and bond lengths of Cu-Ag fcc-like clusters.