Lattice Dynamics of Hexagonal Metals Based on a New Electron Ion Interaction

Abstract

This communication presents a new approach to the lattice dynamics of hexagonal metals in which the electron ion contribution has been introduced in a manner outlined recently by the authors. Three metals with different axial (c⁄a) ratios have been considered: they are beryllium (1.568), magnesium (1.624) and thallium (1.597). The ion-ion interaction has been restricted up to the fifth neighbours for beryllium and upto the fourth neighbours for magnesium and thallium. The force constants have been related with the elastic constants in the long wave length limit. The dispersion curves have been drawn for [0001] and [01\bar10] directions for all the three metals and are found to be in satisfactory agreement with the results of neutron scattering on beryllium and magnesium. No comparison has been made for thallium for lack of experimental data on it.