Physics Events
[PAST EVENT] Physics Colloquium
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- Open to the public
Abstract:
Electronic excitations are fundamental physical processes. Spectroscopic information,
including absorption and emission spectra, from electron or photon probes is crucial for
materials characterization and interrogation. When experimental data are supplemented and
interpreted by first principles atomic modeling, a coherent physical picture can be established
to provide physical insights into the intriguing structure-property-function relationship of
functional materials.
In this talk, the significance of the first principles modeling of electronic excitations is
highlighted with three examples. In the first example, we investigated the oxygen 1s corelevel
binding energy shift of bilayer silica films on Ru(0001) under different surface oxygen
coverages in the X-ray photoelectron spectroscopy (XPS) measurement. Our study revealed
that the binding energy shift is an electrostatic effect caused by the interplay of the surface
and interface dipole moments. In the second example, we applied ab intio X-ray absorption
near edge structure (XANES) modeling for spinel lithium titanate (Li4/3Ti5/3O4), an appealing
lithium ion battery material. We identified key spectral features as fingerprints for quantitative
assessment of the structural transformation during lithiation. In the third example, we are
motivated to develop a local representation of the microscopic dielectric response function of
valence electrons, which is a central physical quantity that captures the many-electron
correlation effects. Although the response function is non-local by definition, a local
representation in real space can provide insightful understanding of its chemical nature and
improve the computational efficiency of first principles excited state methods. We applied the
local dielectric theory to calculate the molecular polarizability of water and investigated the
effects of the local field and hydrogen bonds.
This research used resources of the Center for Functional Nanomaterials, which is a U.S.
DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DESC0012704