Relaxation effects in the vibrations of a lithium fluoride surface

The vibrational frequencies of a 15-layer slab are calculated for a simple shell model of lithium fluoride, and the surface modes occurring are analyzed. The static relaxations of a slab and of a single surface are calculated for the same model, and the effects of the relaxation on the vibrational frequencies are investigated. A puckering distortion of the surface layer is incorporated in the vibrational calculations for the first time and is found in this case to introduce one extra surface mode. © 1983 The American Physical Society.