Refinement of crystal structure parameters using convergent-beam electron diffraction: the low-temperature phase of SrTiO₃

The method to refine crystal structure parameters (atom positions and Debye-Waller factors) using convergent-beam electron diffraction (CBED), which is applicable to crystal structure analysis of a small specimen area down to a few nm in diameter, is studied. The line profiles of higher-order Laue-zone reflections are recorded using imaging plates. Theoretical intensities are calculated based on the dynamical theory of electron diffraction with the aid of the generalized Bethe approximation to shorten calculation time. The structural parameters are determined by fitting the experimental profiles with the theoretical ones using a nonlinear least-squares method. The present method has been applied to the low-temperature phase of SrTiO₃. The structural parameter or the rotation angle of the oxygen octahedron has been determined to be = 1.12 (4)°, which shows good agreement with that obtained from electron spin resonance experiments.

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