Return to list of previous seminars
January 5 No Seminar
January 12 "Electronic structure calculations: an overview, part II"
Prof. Henri Jansen, Department of Physics, Oregon State University
January 19 "Neutron Scattering Studies of Magnetic Semiconductor-Based Nanostructures Part I"
Prof. Tom Giebultowicz, Department of Physics, Oregon State University
January 26 "Neutron Scattering Studies of Magnetic Semiconductor-Based Nanostructures Part II"
Prof. Tom Giebultowicz, Department of Physics, Oregon State University
February 2 "The problem of phase determination in protein crystallography"
Prof. Andy Karplus, Department of BioChem/BioPhys, Oregon State University
February 9 No Seminar
February 16 "Fast photoresponse in organic semiconductors: understanding
POSTPONED the mechanisms and structure-property relationships"
Prof. Oksana Ostroverkhova, Department of Physics, Oregon State University
February 23 "Novel circular resonator with broken angular momentum symmetry"
Alexander Govyadinov, OSU Physics
"Non-Magnetic Negative Refraction Index Materials"
Robyn Wangberg, OSU Physics
March 2 "Tandem time-of-flight mass spectrometry"
Prof. Douglas Barofsky, OSU, Dept. of Chemistry.
The following are seminars given by candiates for our faculty position:
Tuesday 8 March 9:15 am Weniger 304
"Effect of Molecular Environment on Quantum Tunneling
and Magnetic Properties for Single Molecule Magnets"
Dr. Kyunghwa Park, Naval Research Laboratory, Washington D.C.
Friday 11 March 11:00 am Weniger 304
"Real-time dynamics of strongly correlated systems using DMRG"
Dr. Adrian Feiguin, University of California, Irvine CA.
Tuesday 15 March 11:00 am Weniger 304
"Progress in Materials Simulation"
Dr. Paul Kent, University of Cincinnati, Cincinnati,OH
Thursday 17 March 11:00 am Weniger 304
"Density Functional Theory: from conventional bulk to nanoporous materials"
Dr. Julia Medvedeva, Northwestern University, Evanston IL
Abstracts:
Dr. Kyunghwa Park
Center for Computational Materials Science
Naval Research Laboratory
Washington D.C.
It has been demonstrated within density-functional theory (DFT) that it is possible to calculate the electronic
structure and magnetic properties of "pure" isolated single molecule magnets consisting
of several metal ions coupled via oxygen anions and a total number of up to 200 atoms in
high symmetry. In order for single molecule magnets to function as information storage
devices, one needs to understand at the molecular level what types of environmental changes
can significantly influence the exchange couplings, magnetic anisotropy, and observed quantum
tunneling of the magnetic moment in more realistic (experimentally realizable) single molecule magnets.
In this talk, I will consider, within DFT, interactions between different molecules and two types
of disorder which may be present in experimental samples: disorder due to solvent molecules
and possible extra electrons. Contributions of the intermolecular interactions and solvent
disorder to the tunneling will be discussed. The effect of the extra electrons on the exchange
couplings, the total magnetic moment, the magnetic anisotropy, and the tunneling will be
presented as a function of number of extra electrons. In addition, the magnetic anisotropy
parameters obtained from the two kinds of disorder will be compared to each other and experimental data.
Dr. Adrian Feiguin
Department of Physics and Astronomy
University of California
Irvine, CA.
Over the last ten years the density matrix renormalization group (DMRG) method has proven
to be remarkably effective at calculating static, ground state properties of low-dimensional
strongly correlated systems. During the past year, the DMRG has experienced an unprecedented
evolution. Through a convergence with quantum information ideas, it has been recently adapted
to solve the time-dependent Schroedinger's Equation. We present a new time-evolution DMRG
algorithm which works on ladders and systems with interactions beyond nearest neighbors,
in contrast to previous Suzuki-Trotter based approaches. We demonstrate its application
on several chain and ladder systems, and we show how it can be extended to study thermodynamics
of strongly correlated systems.
Dr. Paul Kent
Department of Physics
University of Cincinnati
Cincinnati,OH
In recent years, simulations using density functional theory (DFT) have emerged as the
workhorse method for computational materials simulation. Calculations with around 200 atoms
are becoming routinely possible with reasonable computational requirements. However, radical
improvements in these methods will be required to meet the challenges of accuracy, system
size, and temporal scale posed by modern applied problems in physics, chemistry, and materials
science. In this seminar, I will focus on two novel approaches to extend the applicability of DFT.
I will first give an overview of progress in simulating the high temperature cuprate
superconductors, materials that have resisted explanation since their discovery in 1986.
I will give an overview of the challenges involved in constructing parameter free simulations
of these materials, and present recent results on the temperature of the superconducting
transition that suggests these simulations might indeed be possible. Finally, I will briefly
discuss quantum monte carlo methods. These benchmark accuracy methods provided the key data
upon which modern DFT rests. I will present some new ideas using these methods to improve the utility of DFT.
Dr. Julia Medvedeva
Department of Physics
Northwestern University
Evanston, IL.
Modern computational approaches based on density functional theory (such as the full- potential
linearized augmented plane wave (FLAPW), linearized muffin-tin orbital (LMTO) and Dmol methods)
form a powerful framework for the first-principles modeling of the structural, electronic,
magnetic and optical properties of materials. The increase of computer power as well as
the development and implementation of new algorithms greatly expand the range of the materials
which can be treated. Currently, we are beginning to understand the properties of complex
structures such as nanoporous solids and polymers. I will present my contribution to the
field and possible extensions.