Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:

Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:

Thesis advisor: David Broido === Despite its deceptive simplicity and because of its scientific and technological importance, bcc Fe is still the subject of research and debate. We develop an ab initio theoretical framework and apply it to calculate temperature-dependent phonon modes and magnetic in...

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Main Author: Heine, Matthew
Format: Others
Language:English
Published: Boston College 2020
Subjects:
ab initio
first principles
invar
magnetic
phonon
temperature
Online Access:http://hdl.handle.net/2345/bc-ir:108985
id ndltd-BOSTON-oai-dlib.bc.edu-bc-ir_108985
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spelling ndltd-BOSTON-oai-dlib.bc.edu-bc-ir_1089852021-09-23T05:01:43Z Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar: Heine, Matthew Thesis advisor: David Broido Text thesis 2020 Boston College English electronic application/pdf Despite its deceptive simplicity and because of its scientific and technological importance, bcc Fe is still the subject of research and debate. We develop an ab initio theoretical framework and apply it to calculate temperature-dependent phonon modes and magnetic interaction parameters in bcc Fe. This framework incorporates realistic thermal disorder in a coupled spin-lattice system. Thermal spin-lattice coupling is found to significantly renormalize the phonon modes and magnetic interaction strength, resulting in significant temperature-dependencies. A method for treating magnetic systems of unknown entropy is developed and applied to calculate phonon modes and investigate the anomalous thermal expansion of the classical invar alloy, Fe0.65Ni0.35. Results over the temperature range 50K to room temperature are consistent with the observed low thermal expansion of this material. Excellent agreement with measured data is achieved for calculated phonon modes in both bcc Fe and the invar alloy. ab initio first principles invar magnetic phonon temperature Copyright is held by the author, with all rights reserved, unless otherwise noted. Thesis (PhD) — Boston College, 2020. Submitted to: Boston College. Graduate School of Arts and Sciences. Discipline: Physics. http://hdl.handle.net/2345/bc-ir:108985
collection NDLTD
language English
format Others
sources NDLTD
topic ab initio
first principles
invar
magnetic
phonon
temperature
spellingShingle ab initio
first principles
invar
magnetic
phonon
temperature
Heine, Matthew
Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:
description Thesis advisor: David Broido === Despite its deceptive simplicity and because of its scientific and technological importance, bcc Fe is still the subject of research and debate. We develop an ab initio theoretical framework and apply it to calculate temperature-dependent phonon modes and magnetic interaction parameters in bcc Fe. This framework incorporates realistic thermal disorder in a coupled spin-lattice system. Thermal spin-lattice coupling is found to significantly renormalize the phonon modes and magnetic interaction strength, resulting in significant temperature-dependencies. A method for treating magnetic systems of unknown entropy is developed and applied to calculate phonon modes and investigate the anomalous thermal expansion of the classical invar alloy, Fe0.65Ni0.35. Results over the temperature range 50K to room temperature are consistent with the observed low thermal expansion of this material. Excellent agreement with measured data is achieved for calculated phonon modes in both bcc Fe and the invar alloy. === Thesis (PhD) — Boston College, 2020. === Submitted to: Boston College. Graduate School of Arts and Sciences. === Discipline: Physics.
author Heine, Matthew
author_facet Heine, Matthew
author_sort Heine, Matthew
title Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:
title_short Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:
title_full Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:
title_fullStr Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:
title_full_unstemmed Ab Initio Theory of Thermal Spin-Lattice Disorder in Iron and Invar:
title_sort ab initio theory of thermal spin-lattice disorder in iron and invar:
publisher Boston College
publishDate 2020
url http://hdl.handle.net/2345/bc-ir:108985
work_keys_str_mv AT heinematthew abinitiotheoryofthermalspinlatticedisorderinironandinvar
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