Abstract
The surface phonon dispersion curves of the NiAl(111) surface have heen measured along \overlineΓK of the two dimensional Brillouin zone by means of high-resolution energy loss spectroscopy. The observed dispersion curves were compared with lattice dynamical calculations of a slab shaped crystal on the basis of a force constant model including up to the third nearest-neighbor interaction. Good agreement between the experimental and calculated curves was obtained for two different combinations of the surface force constants, which suggests the existence of two different models concerning the surface atomic relaxation.