Abstract

The electron charge density is of fundamental importance to the physics of materials. It is the redistribution of electrons that occurs when atoms bond which distinguishes materials from collections of independent atoms. It is also the case that the ground state properties of any material system can be determined from the electron charge density. This is the basis of Density Functional Theory (DFT), the most widely used and successful technique for modelling materials at the atomic scale. While DFT has been hugely successful as a tool for modeling materials systems quantum mechanically, the approximations used to make such calculations practical mean that there remains an important role for experiments to verify and inform DFT results. I will first share some recent advances which improve the predictive power of DFT calculations. I will then show how phase imaging in the electron microscopy is sensitive to the effect of charge redistribution from bonding. In particular how electron ptychography, performed in the STEM microscope, provides the necessary sensitivity to detect this subtle effect by directly imaging the charge redistribution. This provides direct comparison to the charge density predicted by DFT simulations.