Michigan Technological University
Department of Physics

is pleased to announce a colloquium

with

Eugene Tsiper

Electronic Polarization in Organic Molecules and Molecular Solids: Classical Interactions Between Quantum Systems

Electronic structure of molecular solids is strikingly different from the conventional inorganic semiconductors, such as Si. Coulomb interactions between molecules in van der Waals contact, narrow bandwidths and localized nature of charges make electronic polarization a major effect, with energy scale greater than transfer integrals or temperature. We present an approach which treats individual molecules rigorously as quantum-mechanical systems subject to classical non-uniform fields of all other molecules. Atom-atom polarizability tensor is introduced to describe self-consistent intramolecular charge redistribution. Dielectric tensors of two representative organic molecular crystals, computed to within experimental accuracy, suggest quantitative predictability of the new approach. We find quantitative agreements in charge carrier energetics with photoelectron and STM data. Applications of the approach range broadly from optical and dielectric response of molecular crystals to charge transport energetics in nanoscale molecular devices to hydrogen bonding and intermolecular forces in biosystems. Calculations for crystalline thin films reveal significant differences in electronic polarization at surfaces, metal-organic interfaces, in thin organic layers, and in the bulk, leading to about 0.5 eV transport gap variations across organic films.

Monday, February 3, 2003

4:00 p.m., Fisher 101

Refreshments will be served

MTU | Physics | Colloquium