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Published January 1, 2017 | Supplemental Material + Published
Journal Article Open

Phonons and elasticity of cementite through the Curie temperature

Abstract

Phonon partial densities of states (pDOS) of ^(57)Fe_3 C were measured from cryogenic temperatures through the Curie transition at 460 K using nuclear resonant inelastic x-ray scattering. The cementite pDOS reveal that low-energy acoustic phonons shift to higher energies (stiffen) with temperature before the magnetic transition. This unexpected stiffening suggests strongly nonharmonic vibrational behavior that impacts the thermodynamics and elastic properties of cementite. Density functional theory calculations reproduced the anomalous stiffening observed experimentally in cementite by accounting for phonon-phonon interactions at finite temperatures. The calculations show that the low-energy acoustic phonon branches with polarizations along the [010] direction are largely responsible for the anomalous thermal stiffening. The effect was further localized to the motions of the Fe_(II) site within the orthorhombic structure, which participates disproportionately in the anomalous phonon stiffening.

Additional Information

© 2017 American Physical Society. Received 22 December 2015; revised manuscript received 5 September 2016; published 20 January 2017. The experimental equipment used in this work benefited from design discussions with Curtis Kenney-Benson and Eric Rod. This work was supported by the Department of Energy through the Carnegie-DOE Alliance Center, funded by the Department of Energy through the Stewardship Sciences Academic Alliance Program. J.E.H. was supported by the Department of Energy Office of Science Graduate Fellowship Program (DOE SCGF), made possible in part by the American Recovery and Reinvestment Act of 2009, administered by ORISE-ORAU under Contract No. DE-AC05-06OR23100. J.L. thanks Dave Walker for assistance with synthesizing the Fe_3C sample and acknowledges support from the Deep Carbon Observatory through the Sloan Foundation, NSF Grant No. AST1344133 and NSF Grant No. EAR1219891. The calculations performed herein were made possible by resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Portions of this work were performed at HPCAT (Sector 16), Advanced Photon Source (APS), Argonne National Laboratory. HPCAT operations are supported by DOE-NNSA under Grant No. DE-NA0001974 and DOE-BES under Grant No. DE-FG02-99ER45775, with partial instrumentation funding by NSF. The Advanced Photon Source is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Attached Files

Published - PhysRevB.95.024308.pdf

Supplemental Material - Cementite_Supplemental.pdf

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Additional details

Created:
August 19, 2023
Modified:
October 24, 2023