Electron-optical imaging of Ti6O11at 1·6 Å point-to-point resolution

Abstract

Image-matching techniques are used to demonstrate that point-to-point resolutions of better than 1·7 A have been obtained for Ti₆O₁₁ using ultra-high-resolution objective lens pole-pieces and a specially constructed goniometer. However, it is important to distinguish between instrumental and structure image resolution. Whereas the former may be as low as 1·6 Å, the latter is approximately 2·8 Å for C₈ = 0·7 mm at 100 kV. It is shown that to take advantage of 1·6 Å instrumental resolution and obtain useful defect structure information, lengthy calculations and demanding experimental requirements must be met. On the other hand, 2·8 Å structure imaging is far less demanding experimentally (focused illumination may be used for example) and the truncated projected-charge-density approximation may be used, at least in the preliminary stages of defect-structure refinement.