Most of the software used to simulate TEM/STEM images completely neglects interatomic interactions in the sample and thus leaves out the effects of charge transfer and chemical bonding. The effect of these interactions on the image is generally small compared to the total charge density, but essential to understanding many important properties of materials. These interactions are especially important for fully quantitative interpretations of TEM/STEM images of certain sample types such as bulk oxides because of the strong ionic bonds, and 2D materials composed of light elements since most of the electrons are involved in bonding. In order to accurately simulate TEM/STEM phase images of these and other such materials, we have employed the CASTEP  code to generate accurate projected potentials which take into account both intra- and interatomic electron interactions. CASTEP uses density functional theory (DFT) to calculate electron densities, which are directly related to the electrostatic potential via Poisson’s equation. These potentials are then used to calculate the projected potentials for use in multislice algorithms to simulate TEM/STEM images. We have added to the functionality of CASTEP so that these projected potentials can be obtained directly from the software, thus allowing us easy and accurate simulation of images with bonding effects included which enables accurate interpretation of experimental images of materials, such as h-BN. Although a similar approach has been used by Kurasch et al. who obtained projected potentials by post-processing output from the WIEN2k software , no one, to our knowledge, has done this with a code which benefits from the use of pseudopotentials such as CASTEP.
 S. J. Clark et al. First principles methods using CASTEP. Zeitschrift fuer Kristallographie, 220(5-6):567-570, 2005.
 Simon Kurasch et al. Beilstein J. Nanotechnol., 2:394-404, 2011.
 The authors gratefully acknowledge funding from the EPSRC under grant number EP/LO15722/1.
To cite this abstract:Timothy Naginey, Peter Nellist, Rebecca Nicholls, Jonathan Yates; Including the effects of atomic bonding in TEM and STEM image simulations. The 16th European Microscopy Congress, Lyon, France. https://emc-proceedings.com/abstract/including-the-effects-of-atomic-bonding-in-tem-and-stem-image-simulations/. Accessed: December 2, 2023
EMC Abstracts - https://emc-proceedings.com/abstract/including-the-effects-of-atomic-bonding-in-tem-and-stem-image-simulations/