LATTICE-DYNAMICS OF ALKALI-METALS

The lattice dynamics of alkali metals is investigated on the basis of a phenomenological model which is consistent with the translational symmetry of a lattice. The potential energy is considered due to (1) ion‐ion and (2) ion‐electron interactions. The contribution to ion‐ion interaction is evaluated applying the valence force field. The contribution to the potential energy from ion‐electron interaction is considered through the screened Coulomb potential. The theoretical model developed is employed to compute the phonon dispersion curves of Na, K, Li, Rb, and Cs. Computed phonon frequencies are used to interpret the Debye characteristic temperatures at different temperatures. The calculated results for phonon dispersion curves and Debye characteristic temperatures compare well with the experimental ones. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA