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Atomistic Computer Simulations of FePt Nanoparticles

Müller, MIchael (2007):
Atomistic Computer Simulations of FePt Nanoparticles.
Darmstadt, Technische Universität, TU Darmstadt, [Online-Edition: urn:nbn:de:tuda-tuprints-7848],
[Ph.D. Thesis]

Abstract

In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion.

Item Type: Ph.D. Thesis
Erschienen: 2007
Creators: Müller, MIchael
Title: Atomistic Computer Simulations of FePt Nanoparticles
Language: English
Abstract:

In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the kinetics of the ordering transition in FePt nanoparticles is finally investigated by assessing the contributions of surface and volume diffusion.

Place of Publication: Darmstadt
Publisher: Technische Universität
Uncontrolled Keywords: nanoparticle, simulation, phase transition, size dependence
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Date Deposited: 17 Oct 2008 09:22
Official URL: urn:nbn:de:tuda-tuprints-7848
License: only the rights of use according to UrhG
Referees: Albe, Prof. Dr. Karsten and Hahn, Prof. Dr. Horst
Refereed / Verteidigung / mdl. Prüfung: 7 February 2007
Alternative Abstract:
Alternative abstract Language
In der vorliegenden Dissertation wird ein hierarchischer Multiskalenansatz zur Modellierung von FePt Nanoteilchen mittels atomistischer Computersimulationen entwickelt. Durch die Wahl unterschiedlicher Detailgrade bei der Beschreibung der interatomaren Wechselwirkungen ist es möglich verschiedenste Zeit- und Längenskalen in den Simulationen abzudecken. Die Methoden reichen von quantenmechanischen Gesamtenergierechnungen kleiner periodischer Systeme zu Simulationen vollständiger Teilchen über lange Zeitskalen mit Hilfe von einfachen Gittermodellen. Durch Anwendung dieser Methoden wird die energetische und thermodynamische Stabilität von nicht-kristallinen vielfach verzwillingten FePt Nanoteilchen untersucht. Unter Einbeziehung der Einflüsse von Teilchengröße, Zusammensetzung und modifizierter Oberflächenenergien durch verschiedene chemische Umgebungen wird anschließend die Thermodynamik des Ordnungs-Unordnungs-Übergangs in FePt Nanoteilchen analysiert. Um Prozesse zu identifizieren, welche die Umwandlungsrate von der ungeordneten in die geordnete Phase reduzieren oder erhöhen können, wird schließlich die Kinetik des Ordnungsübergangs in FePt Nanoteilchen unter Berücksichtigung der Beiträge von Oberflächen- und Volumendiffusion untersucht.German
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