Anisotropic and anharmonic effects through the t-matrix for Low-Energy Electron Diffraction (TMAT V1.1) Original Research Article

We describe how to compute non-diagonal t-matrices related to atoms vibrating in anisotropic and/or anharmonic potentials. The formalism has been implemented in a set of FORTRAN routines that can be easily interfaced with existing Low-Energy Electron Diffraction codes, providing a simple and economical way to describe anisotropy and anharmonicity in multiple-scattering calculations. The method is based on an expansion of the atomic probability distribution function. Two different methods are considered depending on whether the expansion is based on multipoles or on cumulants.