Friday, May 16, 2003, 16:00
WHGA Auditorium
Dr. B. Delley, PSI
Abstract:
The fundamental physical laws of solid state physics and chemistry are
completely known, yet lead to equations much too complicated to be
soluble. Fortunately, the simpler orbital theories cover a large part of
the phenomena of interest qualitatively. With the developments in
density functional theory, orbital theory has become the most accurate
first principles theory available today for a wide class of electron
systems and for all electronic properties qualitatively compatible with
the orbital picture.
Understanding of thermodynamic properties is of interest in a number of
contexts. I will show examples from a growth study of epitaxial layers.
The most stable precursor structure is also the one which is compatible
with tunnel microscopic observation.
Reaction path and energy barriers are of interest in a case of optically
generated metastable states. In this example DFT gives a coherent
picture not only of thermodynamic properties, but also covers optical
excitations and Mossbauer spectroscopic findings.
In an application to molecules at a metal surface with atomic steps,
connection is made to to electron spectroscopic observation of a surface
state showing sensitivity to the chemisorbed species.
Certain ferromagnetic semiconductors are of interest to the emerging
field of 'spintronics'. Density functional results for such compounds
suggest unusual properties like half metalicity, which are relevant to
produce holes with well defined spin in the energy range of interest.
If time permits, I will also touch on species in solution and on transport properties, in particular electrical current through nano-bridges.