Evaluation of Frozen Phonons Models for Multislice Calculation of TDS
نویسندگان
چکیده
The thermo diffuse scattering (TDS) of electrons results in a diffuse background below the Bragg reflections. Accounting for this background is a key point in quantitative treatment of diffraction data [1], for example: the potential or charge density reconstruction [2]. The recent interest in TDS theories and calculations was caused by a wide spread of high resolution STEM imaging [3], because HAADF contrast is mostly determined by TDS [4]. There are a number of methods developed for the calculation of TDS [5-7] whereas the multislice approach based on the frozen phonons model has been most accurate and physically realistic so far [8]. There are a number of questions related to multislice TDS calculations, which were addressed [9,10], but not fully clarified so far: 1 To what thicknesses multislice calculations are accurate? 2 Is the Einstein model sufficient or is a more rigorous consideration of collective atoms movement necessary? 3 Can HOLZ scattering be calculated correctly by the multislice aproach? In order to shed some more light on these and related issues, we are going to study the effect of phonon vibrations in Si derived from classical Molecular Dynamics (MD) and the influence of the treatment of the z-coordinates on parallel and convergent beam electron diffraction (CBED) patterns as well from high angle centered darkfield images calculated by the multislice approach. st
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تاریخ انتشار 2006