n-Beam lattice images. V. The use of the charge-density approximation in the interpretation of lattice images

Abstract

The simple infinite-aperture charge-density approximation to lattice imaging is extended to include the effects of finite aperture and objective-lens spherical aberration. Images computed using these approximations are compared with images computed by the accurate N-beam technique and with experiment in order to establish the bounds of applicability of the extended-charge-density approximations.

High-resolution electron microscopy of molecular crystals. II. Image simulation

“…5; this agrees with similar increases found for images of complex oxides (Lynch, Moodie & O'Keefe, 1975). Similarly, with both types of crystal, increasing thickness increases the image contrast and narrows the range of defocus over which the structure image occurs.…”

Structure determination of SnSb2S4 and SnSb2Se4 by high-resolution electron microscopy

“…Under these conditions the image of a sufficiently thin crystal corresponds to the projected charge density (PCD) of the structure, to a reso!u-I/4 3/4 tion limit of approximately 0.6 x Cs A (=2.2 A). The limits of applicability of the PCD approximation are discussed by O'Keefe (1973) and Lynch, Moodie & O'Keefe (1975). Fig.…”

Electron-microscope and diffraction studies of polytypism in stilpnomelane

“…An image intensification system attached to the EM300 greatly facilitated image recording. Contrast in lattice images was generally poor, the absence of any potential 'tunnels' similar to those in beryl (Buseck & Iijima, 1974) making a PCD interpretation (Lynch, Moodie & O'Keefe, 1975) somewhat difficult. For the characterization of displacement disorders, however, simple fringe images appear to be adequate (Jefferson & Thomas, 1975), and consequently the focus of the objective lens was adjusted to obtain merely optimum contrast for one set of 00l and hkO or Okl fringes, which thereby gave a simple, two-dimensional image.…”