Imaging charge density
Charge density is fundamental to the quantum mechanics of materials and their properties. The phase sensitivity of ptychography is great enough that the transfer of single electrons can be detected.
Below is a comparison of the phases of the B and N sites in WDD ptychography from experimental and simulated data. First the the raw experimental result is shown, then experiment post AC shows the result after performing post collection aberration correction. The IAM show the result simulated using the independent atom model (IAM) which shows the phases expected from potentials from neutral atoms which are not bonded. The DFT result shows the phases expected from potentials using density functional theory (DFT). In each case a histogram of the integrated phase cross sections (IPCS) values is shown.
Notice that correcting for residual aberrations is important as the polarity of the B and N phases are incorrect without it. Notice further that the IAM produces a polarity between the phases of the B and N sites which is far too great compared to the experiment, whereas the DFT potentials match far better.
For further details see our paper on ArXiv.