Dresden 2006 – scientific programme
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MM: Metall- und Materialphysik
MM 33: Symposium Materials Modelling II
MM 33.4: Talk
Thursday, March 30, 2006, 15:45–16:00, IFW A
First Principles Calculations of the Elastic Constants of Fe-Pt Phases — •Nikolay Zotov and Alfred Ludwig — Forschungszentrum Caesar, Ludwig-Erhard-Allee 2, D-53175 Bonn
The electronic structure of the ordered and disordered Fe-Pt phases has been extensively studied during the last two decades by ab-initio methods due to their outstanding electronic and magnetic properties. For example, thin films containing the fct ordered FePt phase are promising candidates for high-density recording media. Their elastic properties have received less attention although the bulk modulus anomaly in FePt alloys is experimentally known since long time. We have carried out a first-principles study of all zero-pressure elastic constants for the ordered Fe-Pt alloys including pure bcc Fe and fcc Pt. The calculations were made using the VASP code implementation of the density functional theory in the generalized gradient approximation (GGA) with Perdew-Wang exchange correlation and projector augmented wave pseudopotentials. The integrations of the Brillouin zone were made on a mesh of 11x11x11 k-points. The calculated elastic constants for bcc Fe and fcc Pt are in good agreement with experimental data and previous calculations. Several trends in the predicted elastic constants are established as a function of the chemical composition. The bulk and shear modulus as well as c11, c12 and c44 have a minimum for the Fe3Pt phase and a maximum for the fct FePt phase. The calculated elastic constants obey all conditions for mechanic stability of the cubic and tetragonal phases but c11−c12 is close to zero for Fe3Pt suggesting a shear instability at this composition.