CALCULATIONS OF THE DYNAMIC DEBYE-SCHERRER DIFFRACTION PATTERNS FOR SMALL METAL PARTICLES

Dynamic diffraction pattern profiles are calculated for randomly oriented aggregates of gold and silver in the size range from 147 to 5083 atoms and at incident electron energies of 40 kV and 100 kV. The Debye-Scherrer diffraction patterns were obtained by combining a series of multislice calculations performed on model particles over a range of-orientations, Calculations are performed for both fee and icosahedral structures. The results show that corrections to the kinematical theory (Debye equation) are more important than predicted by the two-beam theory of Blackman. One calculation, a fee 923-atom silver aggregate at 100 kV, showed a distortion to the (111) Bragg peak causing it to to shift its center to a higher scattering angle. Scattering corrections to the icosahedral results are less important than for an equivalent sized fee aggregate and preserve the general diffraction features seen in kinematic calculations. (C) 1995 American Institute of Physics.