Crystallographic Image Processing (CIP) of a high-resolution electron microscopy (HREM) image of α-Ti2Se recorded with a 300 kV TEM (JEOL 3010 UHR, point resolution 1.7 Å) along the [001] zone axis. In the first step the Fourier transform of the HREM image is calculated (only the amplitudes are shown). The position of the white ring marks the first crossover of the contrast transfer function (CTF) which is used to determine the defocus value (Δf = -650 Å). The reciprocal lattice is then indexed and amplitudes and phases are extracted. The amplitudes and phases can be used to calculate the averaged image for one unit cell via Fourier synthesis. The pseudo-potential map (p2gg symmetry) for determining 2D atomic co-ordinates was obtained after correction of the phase-shifts imposed by the CTF. The average agreement of atomic co-ordinates determined from the pseudo-potential map and the superimposed model from X-ray diffraction is about 0.2 Å.[1]
Crystallographic image processing (CIP) is traditionally understood as being a set of key steps in the determination of the atomic structure of crystalline matter from high-resolution electron microscopy (HREM) images obtained in a transmission electron microscope (TEM) that is run in the parallel illumination mode. The term was created in the research group of Sven Hovmöller at Stockholm University during the early 1980s and became rapidly a label for the "3D crystal structure from 2D transmission/projection images" approach. Since the late 1990s, analogous and complementary image processing techniques that are directed towards the achieving of goals with are either complementary or entirely beyond the scope of the original inception of CIP have been developed independently by members of the computational symmetry/geometry, scanning transmission electron microscopy, scanning probe microscopy communities, and applied crystallography communities.
^T. E. Weirich, From Fourier series towards crystal structures - a survey of conventional methods for solving the phase problem; in: Electron Crystallography - Novel Approaches for Structure Determination of Nanosized Materials, T. E. Weirich, J. L. Lábár, X. Zou, (Eds.), Springer 2006, 235 - 257.
