Prof. James R. Chelikowsky, Center for Computational Materials, Institute of Computational Engineering and Sciences, Department of Physics and Department of Chemical Engineering, UT-Austin

"Mechanically Seeing the Covalent Bond"

Coffee and cookies will be served at 3:45pm in RLM 4.102

Abstract: Recent advances in atomic force microscopy have mechanically rendered images of covalent bonds with an unprecedented resolution, e.g., resolving the bond order. These advances offer the possibility of imaging the internal chemical structure of individual molecules, which is a "dream come true." Still, fundamental questions remain about interpreting such images. While most features in the measured images have a close correspondence to the atomic structure of a given specimen, some cannot be so interpreted. Also, the nature of the probe tip can be crucial in understanding the details of the image, but often the atomic structure of the tip is unknown. In order to simulate an atomic force image, one must calculate accurate interatomic forces as a function of the tip height. The required calculations are intense as they may involve thousands of atoms for a like number of different geometries. Such calculations are traditionally outside of our capability, even with contemporary computational platforms. I will illustrate how new algorithms and computational methods for simulating atomic force microscopy images can address these computational hurdles and result in simulations that often replicate the measured images in subatomic detail.