TREATMENT OF THERMAL VIBRATIONS AND LOCAL STATIC DISORDER WITHIN TENSOR LEED

A general formalism is developed to include thermal vibrations and local static disorder into tensor-LEED calculations. The given expression for the averaged t matrix is based on a cumulant expansion for the probability distribution of atomic displacements. The method is a generalization of the concept of temperature-dependent scattering phase shifts and allows an efficient description of both anisotropy and anharmonicity of thermal motions, which are important in particular for adsorbate atoms and substrate atoms in the topmost layers.