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A polyamorphous fragile to strong transition under equilibrium cooling in a simple monatomic liquid
Stockholm University, Faculty of Science, Numerical Analysis and Computer Science (NADA).
KTH, Numerisk analys och datalogi (NADA), (tills m SU), Numerical Analysis and Computer Science (NADA) (together with SU).
KTH, institutionen för materialvetenskap.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Glass transition remains one of the deepest and most interesting  problems of condensed-matter physics. One fundamental aspect of the problem is how to avoid  crystalline nucleation when cooling a liquid towards the glass  transition at an arbitrarily slow rate. The prototype ``ideal glass  formers'' are silica and other inorganic network-forming systems. No  monatomic glass has been obtained so far by cooling from melt.  Whether a monatomic system can reproduce the behavior of  silica-like glass formers is a question of great interest, both  conceptual and for technological applications. We present a  molecular-dynamics simulation of a simple monatomic system based on  a metallic-like pair potential. We demonstrate that, while remaining  stable with respect to crystallization, the system performs under  cooling a first order phase transition from a fragile to an  extremely strong liquid state. The low-temperature  liquid phase can be cooled to a state of very high viscosity and low  diffusivity while remaining in equilibrium. This result may provide  a significant insight into the formation mechanisms of metallic  glasses.

National Category
Natural Sciences
URN: urn:nbn:se:su:diva-29018OAI: diva2:228578
Available from: 2009-08-04 Created: 2009-08-04 Last updated: 2013-07-09Bibliographically approved
In thesis
1. Computer Simulations of Simple Liquids with Tetrahedral Local Order: the Supercooled Liquid, Solids and Phase Transitions
Open this publication in new window or tab >>Computer Simulations of Simple Liquids with Tetrahedral Local Order: the Supercooled Liquid, Solids and Phase Transitions
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The understanding of complex condensed matter systems is an area of intense study. In this thesis, some properties of simple liquids with strong preference for tetrahedral local ordering are explored. These liquids are amenable to supercooling, and give complex crystalline structures on eventual crystallisation. All liquids studied are simple, monatomic and are similar to real metallic liquids.

The vibrational density of states of a glass created in simulation is calculated. We show a correspondence between the vibrational properties of the crystal and the glass, indicating that the vibrational spectra of crystals can be used to understand the more complex vibrational spectra of the glass of the same substance.

The dynamics of supercooled liquids is investigated using a previously not implemented comprehensive measure of structural relaxation. This new measure decays more slowly in the deeply supercooled domain than the commonly used measure.

A new atomic model for octagonal quasicrystals is presented. The model is based on findings from a molecular dynamics simulation that resulted in 45˚ twinned β-Mn. A decoration is derived from the β-Mn unit cell and the unit cell of the intermediate structure found at the twinning interface.

Extensive simulations are used to explore the phase diagram of a liquid at low densities. The resulting phase diagram shows a spinodal line and a phase coexistence region between a liquid and a crystalline phase ending in a critical point. This contradicts the old conclusion of the Landau theory -- that continuous transitions between liquids and crystals cannot exist

The same liquid is explored at higher densities. Upon cooling the liquid performs a first order liquid-liquid phase transition. The low temperature liquid is shown to be strong and to have very good glass forming abilities. This result offers new insights into fragile to strong transitions and suggests the possibility of a good metallic glass former.

Place, publisher, year, edition, pages
Stockholm: Numerical Analysis and Computer Science (NADA) (together with KTH), Stockholm University, 2009. vi, 65 p.
Trita-CSC-A, ISSN 1653-5723 ; 2009:14
Simple liquids, glasses, liquid-glass transition, supercooled liquids, tetrahedral liquids, phase transitions, quasicrystals, molecular dynamics
National Category
Condensed Matter Physics Condensed Matter Physics
Research subject
Numerical Analysis
urn:nbn:se:su:diva-27876 (URN)978-91-7155-901-2 (ISBN)
Public defence
2009-09-11, Sydvästra galleriet, Biblioteket, Kungl Tekniska Högskolan, Osquars backe 25, Stockholm, 10:15 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: In progress. Available from: 2009-08-20 Created: 2009-05-27 Last updated: 2009-08-27Bibliographically approved

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Elenius, Måns
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