Acoustic waves and phonon focus in Li crystal: the first principle study

摘要

The acoustic waves in Li are investigated by solving the Christoffel equations. Theoretical calculations of the three dimensional slowness surfaces give insights into the mixing of longitudinal and transverse modes and show the origin of the phonon caustics. The results are explained in terms of phonon focusing due to the anisotropy of crystals. The propagation of elastic waves in Li is affected by the elastic anisotropy of the lattice.