Phonon Spectra and Thermal Properties of Some fcc Metals Using the Embedded-Atom Method

Abstract

By employing the analytic embedded-atom potentials of Mei {\it et al.} [Phys. Rev. B 43, 4653 (1991)] we have calculated the phonon dispersion spectra for six fcc metals: Cu, Ag, Au, Ni, Pd and Pt. We have also investigated thermal properties of these metals within the quasiharmonic approximation. Results for the lattice constants, coefficients of linear thermal expansion, isothermal and adiabatic bulk moduli, heat capacities at constant volume and constant pressure, Debye temperatures and Grüneisen parameters as a function of temperature are presented. The computed results are compared with the available experimental data. The comparison shows a generally good agreement between the calculated and experimental values for all thermodynamic properties studied. Isothermal and adiabatic bulk moduli and the specific heats are reproduced reasonably well, while the Grüneisen parameter and Debye temperature are underestimated by about 10%. The calculated phonon frequencies for Ag and Cu agree well with the results from inelastic neutron scattering experiments. However, there is considerable room for improvement in the phonon frequencies for Ni, Pd, Pt and Au, particularly at high phonon wave vectors close to the Brillouin zone boundary. The coefficient of linear thermal expansion is underestimated in most cases except for Pt and Au. The results are good for Pt up to 1000K and for Au up to 500 K.