Correction for the dynamical electron diffraction effect in crystal structure analysis

A method is proposed to correct for the dynamical electron diffraction effect in crystal structure analysis. A rough structure model is first obtained by conventional structure-analysis methods neglecting the dynamical diffraction effect. From the rough structure model, multislice calculations are used to estimate the crystal thickness through the observed dynamical diffraction wave amplitudes. With this estimated thickness, the observed diffraction wave amplitudes are calibrated to give a set of fictitious observed kinematic structure-factor magnitudes. Based on such a set of magnitudes, a traditional least-squares procedure is used to refine structural parameters. The reliability of the result is checked by the consistency between the observed dynamical diffraction wave amplitudes and those found from the multislice calculation. The process can be made iterative. Tests were performed with two known structures, Bi-2212 and Pb-doped Bi-2223 high-T_c superconductors, and satisfactory results were obtained.