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MM: Metall- und Materialphysik

MM 25: Poster Session

MM 25.3: Poster

Mittwoch, 29. März 2006, 15:30–17:30, P4

Calculation of the Excess Volume of an Edge Dislocation by MD-Simulations — •Bernd Eberhard^1,2, Rolf Anders², and Ferdinand Haider² — ¹OSRAM GmbH, Mittelstetter Weg 2, 86830 Schwabmünchen — ²Universität Augsburg, Institut für Physik

Edge as well as screw dislocations should not change the density of metallic systems within linear theory of elasticity, as dilatoric and compressive contributions to the density should be balanced. Taking second order displacements into account, this cancellation is not at all perfect, so that a net contribution of dislocations to the density could be expected. In present work, this effect of nonlinearity is reviewed with selected examples.

We prepared an fcc-lattice with edge dislocations using linear elasticity theory. This was then relaxed in an MD-simulation with variable periodic boundary conditions and the resulting volume per atom was compared to a perfect fcc-lattice. In addition to the average volume the spatial distribution of the excess volume was determined by constructing Voronoi polyhedra around all atoms.

Likewise an ab initio derived EAM interaction scheme for tungsten is used to derive the equilibrium state of a single edge dislocation with emphasis on special boundary conditions which take care of the far reaching displacement fields of dislocations. Also, the Peierls stress of the first kind was derived with proper strains applied to the cell.