Warren E. Pickett

Distinguished Professor
Department of Physics
University of California Davis
One Shields Avenue
Davis CA 95616
Tel: (530)220-2138
Fax: (530)752-4717


PhD 1975 SUNY Stony Brook
MS 1971 Wichita State Univeristy
BS 1969 Wichita State University

Listing in UC Davis Physics Faculty collection

List of Honors, Awards, Activities

Our Research Goals and Methods

The theory of the behavior of electrons in condensed matter is highly developed, and the implementation in computer codes has progressed enough, that a good deal of the important basic properties of materials can be obtained from "first principles," that is, without input from experiment. On the other hand, there are still many exceedingly interesting phenomena that cannot yet be address from the first principles viewpoint.

Our aim is, first, to apply the successful computational theories to further our understanding of condensed matter systems and to obtain insight into what is still lacking, and then second, to extend the method to describe properties more accurately and to address more phenomena. This programme requires a broad outlook, but once a project is chosen we focus on it in great detail.

Selected Visualizations of Work:

  • Isosurface plot of the charge rearrangement due to covering a diamond surface with oxygen and then cesium. The purple spheres represent carbon atoms (sorry about the hue). Oxygen atoms are green; the cesium adsorbates are blue. All atoms were relaxed to their minimum energy configuration. The isosurfaces show the charge rearrangement when spherical Oxygen and cesium atoms are placed on the diamond surface, then the charge is allowed to flow as it wants. The 'copper' colored surface indicates charge depletion, the 'silver' colored one show charge accumulation. A complex charge dipole layer results, which raises the potential of the interior with respect to the vacuum. The resulting system is a negative electron affinity system, in which any electron excited into the conduction bands near the surface will spontaneously eject from the surface. This effect is very useful for cold cathodes and for flat panel displays, for example.

  • Step on the diamond (111) surface, with colors indicating the local energy of the atom.
    Work done with Brian Davidson.

  • Isosurface plot of the active electron orbital in the electride Cs 3-crown-6. What is an electride? It is an ionic crystal in which a molecule loses an electron and thereby becomes the cation, and the electron locates itself in an interstitial position and by itself, that is, without an atom or a molecule, become the anion. It seems clear, from the joint implication of our theoretical work and the experimental data, that in this molecular crystal the valence electron of the Cs atom sits in the open interstice and thereby stabilizes the crystal. The plot shows an isosurface of the density of the 'electride state' in the interstitial region of the crystal. Blue atoms are oxygen, red atoms are carbon, orange atoms are hydrogen. Our results also suggest that this system is a Mott insulator, and might form an excellent realization of a system described by the simple single band Hubbard model without orbital degeneracy lurking to cause complications.
    Work done with David Singh, Henry Krakauer, and Cree Haas.