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

Abstract

The method to refine crystal structure parameters (atom positions and Debye-Waller factors) using convergentbeam electron diffraction (CBED), which is applicable to crystal structur~ 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 leastsquares 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 qo --1.12 (4) °, which shows good agreement with that obtained from electron spin resonance experiments.

Advances in computational studies of energy materials

“…• (Tsuda & Tanaka 1995). It was assumed that the rotational and tilting distortions in the orthorhombic structure would be similar (much lower, for example, than in barium titanate).…”

Twenty years of structure research on quasicrystals. Part I. Pentagonal, octagonal, decagonal and dodecagonal quasicrystals

“…This method allows, for instance, deriving the full point group symmetry of the sample (Tanaka, 1994) instead of just the Laue class. One can even quantitatively refine the parameters of a trial structure model by fitting the line profiles of the high-order Laue-zone (HOLZ) reflections (see, for instance, Tsuda, Tanaka, 1995). Thus, by this method it is possible to determine the structure of a cluster, for instance.…”

Role of intrinsic disorder in the structural phase transition of magnetoelectric EuTiO3

“…In the tetragonal phase, short (Eu-O2) and long (Eu-O2 ) distances are generated by the displacement of the O2 position. In perovskites, the out-of-phase tilting angle of TiO 6 octahedra (φ − ), as calculated from the refined values of the 30 has been proposed as the primary order parameter of the P m-3m to I 4/mcm displacive transition of the average structural model. Figure 5 shows the values obtained from our refinements as a function of temperature, as listed in Table I.…”