A pseudopotential calculation of the phonon spectrum of aluminium

The phonon dispersion curves for Al are calculated from a theory based on Coulomb interactions among the ions and a local pseudopotential interaction between ions and conduction electrons. Conduction electron correlations are taken into account according to a theory of Singwiet al. ^1,2. A dielectric constant is constructed which satisfies the compressibility sum rule. This is especially important for longitudinal phonons. The agreement of the computed frequencies with the experimental dispersion curves of Stedman and Nilsson³ is good. Sites, sizes and widths of Kohn anomalies in the dispersion curves are also calculated. As expected the theoretical curves show larger anomalies than the experimental data. Finally a comparison is made with the recent calculations of Wallace⁴.