ANALYSIS OF THERMAL VIBRATIONS AND INCOMMENSURATE LAYERS BY LOW-ENERGY-ELECTRON DIFFRACTION

The multiple scattering theory of LEED is briefly reviewed, and recent developments concerning the analysis of thermal vibrations with LEED and the analysis of lattice modulations in incommensurate layers are d iscussed. Usually only isotropic thermal vibrations have been consider ed in LEED structure analyses. This restriction can be overcome by an extension of the theory to anisotropic and anharmonic vibrations, allo wing not only a higher precision in the determination of structure par ameters but also the study of dynamical processes with LEED. In the ca se of incommensurate layers the satellite reflections arise from multi ple diffraction as well as from modulations in the adsorbate or substr ate lattice. It is shown that an approximation can be introduced in th e multiple scattering formalism to calculate the satellite intensities . The method can be applied to incommensurate layers as well as to hig her order commensurate layers.