A shell-model analysis of the structure and dynamics of crystal edges of alkali halides

The static relaxation and the lattice dynamics of rectangular edges of quadratic bars of four rock-salt-structured alkali halides is calculated using a shell model. The relaxation includes a large-scale contraction of the bar as well as tip-localized microscopic static displacements. The phonon spectra of relaxed quadratic bars are presented and modes localized at the edges are identified.