When fast electrons (50kV-1MV) pass through a transmission electron microscope specimen they can loose energy by exciting electrons associated with atoms in the spectrum. The distribution of transmitted electrons as a function of energy loss is called an energy loss spectrum. There are sharp increases in intensity known as an inner shell edges when the energy loss is equal to the binding energy of an inner shell electron. These features can be used for microanalysis, and in my earlier work I used various atomic physics (Hartree-Fock-Slater, Dirac-Fock) programs to calculate appropriate ionisation cross sections. I am now more interested in understanding the near edge structure and using it to give information about bonding, coordination and charge transfer on an atomic scale. I have been applying various approaches based on modern electronic structure techniques (Full Potential Linearised Augmented Plane Wave (FLAPW), Layer Korringa Kohn Rostoker (LKKR), Pseudopotential) to the calculation of the densities of unoccupied states and the resulting near edge fine structures.
Past Graduate Students Involved in This Work: X Weng, J. Auerhammer,
J. Alvarez
LKKR calculation for O K edge in TiO2Solid line calculation, dashed line experiment |
Pseudopotential calculation for C K edge in diamond, solid line experiment. |
Some representative publications