David Prendergast

LBNL Staff Scientist

dgprendergast@lbl.gov
phone: 510-486-4948

Education
B.Sc. Physics and Mathematics, University College, Cork, Ireland
Ph.D. Physics, University College, Cork, Ireland
Postdoctoral Fellow Lawrence Livermore National Lab, Lawrence Berkeley National Lab

General Research Interests
My research is focused primarily on simulating the excited state properties of materials, with particular emphasis on electronic excitation. The aim is to enable reliable and predictive simulations of materials and their spectroscopy, bridging the gap between materials modeling and experiment. To this end, I write computational software which simulates the electronic structure and spectroscopy of a wide range of materials from first principles by taking advantage of High Performance Computing. Within the Theory Facility of the Molecular Foundry, I contribute to its User Program in the area of Computational Method Development and Algorithms.

X-ray spectroscopy is widely used throughout the physical and biological sciences to characterize materialsby directly accessing their electronic structure. Such experiments are carried out at the Advanced Light Source (just alking distance from the Molecular Foundry). A significant part of my research is devoted to improving our ability to accuately predict the x-ray spectroscopy of materials. In particular, I simulate the x-ray absorption spectroscopy (XAS) of aqueous systems and nanostructures, paying particular attention to changes induced by finite temperature/atomic vibrations, solvation/pH, and exploring how such spectroscopy can resolve timescales relevant to ultrafast processes such as bond-breaking, charge transfer, and phase transitions.

At lower photon energies, one can examine fine details of the valence electronic structure of materials. To this end I use many-body electronic structure techniques to compute the excited state properties of materials from first-principles. Accurate quasi-particle band structures are computed using the GW approximation to the electron self-energy, and excitonic states with accurate accounting of electron-hole binding are calculated by solving the Bethe-Salpeter equation. These approaches are applied to complex nanostructures, such as carbon nanotubes, which exhibit strong excitonic effects due to quantum confinement.

MSD Research Projects:

Molecular Foundry: the Theory of Nanostructured Materials Facility program

Personal Website: http://nanotheory.lbl.gov/people/prendergast.html
http://www.foundry.lbl.gov/science/theory/theory_staff-prendergast.html

Figure: Isosurfaces (red) of the highest occupied (top) and lowest unoccupied (bottom) electronic states of a tapered silicon nanowire. The highest occupied level is found to be localized at the narrowest region of the wire, the lowest unoccupied level at the thickest. Our results suggest that electron-hole separation, important for photovoltaic device operation, can be facilitated in nanostructures through morphological design.