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Article
Magneto-structural transformations via a solid-state nudged elastic band method: Application to iron under pressure
Journal of Chemical Physics
  • Nikolai A. Zarkevich, Ames Laboratory
  • Duane D. Johnson, Iowa State University
Document Type
Article
Publication Version
Published Version
Publication Date
1-1-2015
DOI
10.1063/1.4927778
Abstract

We extend the solid-state nudged elastic band method to handle a non-conserved order parameter, in particular, magnetization, that couples to volume and leads to many observed effects in magnetic systems. We apply this formalism to the well-studied magneto-volumecollapse during the pressure-induced transformation in iron—from ferromagnetic body-centered cubic (bcc) austenite to hexagonal close-packed (hcp) martensite. We find a bcc-hcp equilibrium coexistence pressure of 8.4 GPa, with the transition-state enthalpy of 156 meV/Fe at this pressure. A discontinuity in magnetization and coherent stress occurs at the transition state, which has a form of a cusp on the potential-energy surface (yet all the atomic and cell degrees of freedom are continuous); the calculated pressure jump of 25 GPa is related to the observed 25 GPa spread in measured coexistence pressures arising from martensitic and coherency stresses in samples. Our results agree with experiments, but necessarily differ from those arising from drag and restricted parametrization methods having improperly constrained or uncontrolled degrees of freedom.

Comments

The following article appeared in J. Chem. Phys. 143, 06477 (2015) and may be found at http://dx.doi.org/10.1063/1.4927778.

Rights
Copyright2015 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Copyright Owner
American Institute of Physics
Language
en
File Format
application/pdf
Citation Information
Nikolai A. Zarkevich and Duane D. Johnson. "Magneto-structural transformations via a solid-state nudged elastic band method: Application to iron under pressure" Journal of Chemical Physics Vol. 143 Iss. 6 (2015) p. 06477
Available at: http://works.bepress.com/nikolai_zarkevich/17/