Regensburg 2007 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 20: Poster session
MM 20.15: Poster
Tuesday, March 27, 2007, 14:45–18:00, Poster C
Calculation of the Peierls stress from atomistic simulations for bcc tungsten: screw vs. edge dislocations — •Bernd Eberhard1,2, Juergen Almanstoetter2, and Ferdinand Haider1 — 1Universität Augsburg, Institut für Physik — 2OSRAM GmbH, Mittelstetter Weg 2, 86830 Schwabmünchen
For bcc metals, it is commonly assumed, that the mobility of screw dislocations is significantly lower than that of edge dislocations and, therefore, should control the low temperature plastic deformation behaviour. The mobility of dislocations depends on their Peierls energy barrier, defined as the activation energy required to move a dislocation in an otherwise perfect crystal. This connection between atomistic features and the overall mechanical behaviour makes a more detailed investigation of the atomistic system necessary. Also, the violation of Schmid’s Law, stating that the critical resolved shear stress is constant and independent of the slip system and the external stress, is an important ingredient for the construction of macroscopic flow rules of the material, suitable e.g. for finite element calculations.
In present work, these effects are studied for 1/2a<111> screw and edge dislocations in tungsten.
To this end, we constructed dislocation dipoles using elasticity theory in a periodic simulation cell. After relaxation within a NPT MD-simulation, we applied an external shear stress to the system in order to force the dislocations to move at low simulation temperatures. The Peierls energy barriers and the corresponding Peierls stresses are derived.