Soft matter, and the many flavours of diffraction tomography

Abstract

With the arrival in 2009 of diffraction tomography for crystal structure solution [1] of sub‐micron sized crystals, there has been a renaissance in the application of electron diffraction, with diffraction tomography providing a relatively easy path to quantitative analysis of crystal structures, compared to more conventional electron diffraction approaches. The collection of diffraction tomography data occurs by tilting the crystal around an arbitrary axis, which runs counter to the traditional notions of electron diffraction from low index orientated zones. Given the success of the method, it has produced a series of derivative techniques on this theme, of collecting tomographic diffraction from around an arbitrary axis. Each of these methods comes with its strengths and weaknesses. An investigation into the relative merits of the various diffraction tomography techniques, ADT[1], RED[2], EDT[3], Rotation method[4], MicroED[5]. With an emphasis on the application of the techniques for soft matter and radiation sensitive materials, such as organic and protein crystals. Evaluation of the nuances in data collection strategies, hardware requirements, specimen requirements, and optional components, will all be considered, with details of how they affect the experimental setup, data acquisition, and processing. We will discuss the need for validation of structural models and the added difficulties presented in doing so with soft matter materials, often leading to the requirement of validation by additional techniques.