Simulating electron microscopy data from first principles

Modern aberration-corrected electron microscopes combine sub-atomic resolution with the collection of chemical information.  This has been used, for example, to probe individual impurity atoms in graphene by looking at changes in the spectroscopic signal.  Interpreting the chemical information is often aided by computer simulation.  Codes which simulate spectroscopic spectra usually treat the incoming electron as a plane wave, but simulations carried out assuming plane wave illumination do not include information about the probe position and as such are limited in their ability to explain position-dependent data.  Often, the interesting thing about the chemical information is how it changes with position across a material and how that effects the macroscopic properties.  With the growing number of aberration-corrected electron microscopes it is vital to be able to carry out spectroscopic simulations which include the electron beam (i.e. the effects of convergence and position dependence).  This project would developing the theory and modifying a density-functional theory code to include the effects on the beam position.  The code would then be used to interpret experimental data from cutting-edge materials problems such as the oxidation of MoS₂single layer catalysts.