STATIC FLUCTUATION DISTRIBUTIONS AND THEIR INFLUENCE ON DIFFRACTION PATTERNS

Probability distributions of fluctuations of atomic positions around s cattering vector dependent reference lattice points have been calculat ed for various crystalline and quasicrystalline structures, and their influence on the diffraction pattern has been discussed. For incommens urate scattering vectors flat fluctuation distributions are found, whi ch change drastically when the scattering vector approaches the diffra ction peak position. Moments of these distributions have been used to calculate the diffraction pattern. Limitations of the Debye-Waller app roximation are discussed and a new more accurate method of peak intens ity estimation is proposed and tested for real space and phason space fluctuations.