Actions for Magneto-structural transformations via a solid-state nudged elastic band method [electronic resource] : Application to iron under pressure

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Magneto-structural transformations via a solid-state nudged elastic band method [electronic resource] : Application to iron under pressure

Published
Washington, D.C. : United States. Dept. of Energy, 2015.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description
Article numbers 064,707 : digital, PDF file
Additional Creators
Ames Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
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-volume collapse during the pressure-induced transformation in iron—from ferromagnetic body-centered cubic (bcc) austenite to hexagonal close-packed (hcp) martensite. We also 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. Furthermore, 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.
Report Numbers
E 1.99:is-j--8658
is-j--8658
Subject(s)
Note
Published through SciTech Connect.
08/14/2015.
"is-j--8658"
Journal of Chemical Physics 143 6 ISSN 0021-9606; JCPSA6 AM
Zarkevich, N.; Johnson, D.
Funding Information
AC02-07CH11358
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