LARGE ZERO-POINT FLUCTUATIONS OF THE K(110) SURFACE

First-principles calculations have been performed for the clean K(110) surface. The results provide no evidence for the existence of a 0.23 angstrom shear displacement of the surface layer along the [110BAR] direction as was inferred from an analysis of low-energy electron diffraction I-V profiles [Itchkawitz et al., Phys. Rev. Lett. 68, 2488 (1992)]. They do indicate, however, that the surface layer undergoes large-amplitude vibrations (approximately 0.45 angstrom root mean squared) along the [110BAR] direction and it is argued that this feature accounts for the experimental observations.