Dresden 2006 – wissenschaftliches Programm

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SYMM: Multi-ferroic materials

SYMM 1: Multiferroic Materials - Theory

SYMM 1.3: Hauptvortrag

Dienstag, 28. März 2006, 15:30–16:00, HSZ 04

Modelling realistic ferroic materials - multiscale approaches — •S. Gemming, I. I. Chaplygin, W. Alsheimer, and G. Seifert — Institut für Physikalische Chemie, TU Dresden, D-01069 Dresden

The complex coupling of electronic and structural degrees of freedom in ferroic materials makes it necessary to treat different physical properties on a different theoretical level. First-principles calculations based on the density-functional theory yield electronic and atomistic structure, potential and field distribution, as well as dielectric properties. Pure bulk or composite compounds, but also nanostructured species and systems including defects such as grain boundaries and vacancies can thus be investigated at the microscopic scale. Beyond this, the calculations provide a database for mesoscopic approaches, for instance for the conductivity mediated by both electronic and ionic contributions. Also the coupling between different spin subsystems in correlated systems is much better described by a modified Heisenberg approach, whose parameters can be based on first-principles data. In this way the phase sequence and transition temperatures in ferroic oxides have been accessed. Examples for bridging the microscopic and macroscopic length scales are provided by finite-element modelling of the elastic properties of realistic compounds, which contain microscopic defects, or by mean-field approaches to derive the long-range potential or field distribution of nanostructured matter.