Regensburg 2000 – scientific programme

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SYMT: Martensitic Transformations and Shape Memory Effect

SYMT 1: Basics

SYMT 1.3: Invited Talk

Wednesday, March 29, 2000, 14:50–15:20, H16

Simulations of Martensitic Transformations — •P. Entel — Theoretical Physics, Gerhard-Mercator University, D-47048 Duisburg, Germany

We discuss displacive phase transitions in non-magnetic and magnetic alloys on a microscopic level by using first-principles and molecular-dynamics simulations. The ab initio calculation of chemical, elastic, mixing and total energies and elastic constants of the alloys in the different crystal structures allows to predict trends for martensitic instabilities. In the molecular-dynamics study effective potentials have been used which were derived by the Embedding Atom Method. For the non-magnetic alloys the simulations confirm the Hume-Rothery type of behavior. In addition we find that the composition dependent population/depopulation of the antibonding 3d states deep below the Fermi level can play a decisive role. For magnetic alloys like Fe-Ni, which exhibit a large hysteresis, the simulations reproduce fairly well the austenitic transformation upon heating, while for the martensitic transformation upon cooling a large amount of defects is needed.