Professor Alexander F. Moodie 75 years

Retrieval of the projected potential by inversion from the scattering matrix in electron–crystal scattering

A method to otain the crystal potential from the scattering matrix in high-energy electron diffraction is proposed.

Dynamic inversion by the method of generalized projections

A method for determining crystal structures directly from dynamical transmission electron diffraction patterns is given. This solves the phase problem.

Simulations for imaging with atomic focusers

Simulations of the transmission of 200 keV electrons through and beyond `atomic focuser' crystals establish the conditions for using such crystals to obtain ultra-high-resolution electron micrographs of thin samples.

A study of Li₂TiOSiO₄ and Li₂TiOGeO₄ by X-ray powder and electron single-crystal diffraction, ¹⁷O MAS NMR and O K-edge and Ti L_2,3-edge EELS

Diffraction techniques using both X-rays and electrons are used to obtain bond lengths and geometry, and spectroscopic techniques of electron energy-loss spectroscopy and nuclear magnetic resonance to obtain information on energy levels and local environment of the titanium and oxygen atoms in lithium titanium silicate and lithium titanium germanate.

Real-space Green's-function approach within RHEED

Green's-function techniques are used to obtain a real-space-series solution for elastic reflection high-energy electron diffraction from a crystalline surface. A renormalized perturbation expansion due to potential self-scattering is developed for the local real-space Green's function.

High-resolution electron-microscope images of crystals with correlated atomic displacements

A coordinate-space, multislice description of electron scattering from crystals with correlated atomic displacements is constructed. It is used to find expressions for high-resolution electron-microscope images of crystals with static displacements (as in modulated structures) or dynamical displacements (as generated by photons) and, in particular, to determine the translational symmetry of these images.

Schemes to determine the crystal potential under dynamical conditions using voltage variation

Methods to retrieve the electron scattering potential under dynamical diffraction conditions using measurements at two closely spaced voltages are proposed. A non-linear refinement procedure is required when only diffracted intensities are available, a more direct method can be implemented using the full complex exit-surface wave function.

Boron nitride cones: structure determination by transmission electron microscopy

The structure of a novel type of boron nitride whisker was determined by transmission electron microscopy. The whiskers were found to be helical cones with a square-like apical defect.

Experimental and theoretical characterization of structure in thin disordered films

A method of developing a detailed model of the structure of network solids from diffraction data is presented. The method refines a prediction based on first-principles molecular dynamics with the reduced density function determined from diffraction data.

Three-phase structure invariants and structure factors determined with the qu­antitative convergent-beam electron diffraction method

Quantitative convergent-beam electron diffraction is used to determine structure factors and three-phase structure invariants. The refinements are based on centre-disc intensities only.

A `three-beam' analysis of resonance scattering in reflection high-energy electron diffraction

Using the three-beam approximation to the many-beam diffraction equations of electron diffraction, expressions are derived for the coefficient of reflection from a crystal surface and for the depth of penetration of the primary beam into the bulk. The expressions are used to analyse the increase in reflectivity that occurs when a surface resonance condition is established.

Divergent-beam technique used in a SEM to measure the cell parameters of isotopically distinct samples of LiF over the temperature range ∼15–375 K

Cell parameters were determined from the ratio of lines joining conic intersections on divergent-beam photographs. The results were compared with ratios from computer-generated divergent-beam patterns to assess the usefulness of the technique.

Towards an exit wave in closed analytical form

A simple but sufficiently accurate expression is obtained for the exit wave of a crystal in zone-axis orientation. The exit wave at each atom column can be parametrized with only one parameter, which is a function of the projected `weight' of the column.

The role of projection operators in the theory of N-beam diffraction and the inversion of three-beam elastic scattering intensities

The algebra is given for the recovery of phase and amplitude for centrosymmetric and noncentrosymmetric cases from a three-beam convergent-beam electron diffraction pattern. The algebra is available in Mathematica format.

Disorder, superlattice canting and chiral domains in zirconia–niobia ceramic alloys

The structures of the alloy phases Nb₂Zr_x−2O_2x+1 are reviewed and their observed disorder discussed. It is suggested their behaviour can be modelled by a lattice of frustrated XY-type spins (rotations) of the oxygen ion nets.

A two-phase charge-density real-space-pairing model of high-T_c superconductivity

A new model of high-T_c superconductivity is presented based upon the pairing of holes in real space, the pairing mechanism being magnetic exchange coupling. It is suggested that the CuO₂ planes have regions of two different charge densities.

Decoherence in electron backscattering by kinked dislocations

A model is proposed that explains the origin of the bright contrast of dislocation walls consisting of edge dislocation dipoles in electron channelling contrast images (ECCI) of fatigued crystals, when the incident beam is parallel to the edge dislocations.

X-ray multislice computation using the Moodie–Wagenfeld equations: divergent-beam pattern simulation in three-beam and six-beam Laue cases

Pattern simulations for three-beam and six-beam X-ray diffraction are presented using multislice calculations based on Moodie & Wagenfeld's formulation of the X-ray equations, which factorize Maxwell's equations into Dirac format, using circular-polarization bases.