Change search
ReferencesLink to record
Permanent link

Direct link
Structural model for octagonal quasicrystals derived from octagonal symmetry elements arising in beta-Mn crystallization of a simple monatomic liquid
Stockholm University, Faculty of Science, Numerical Analysis and Computer Science (NADA) (together with KTH). (Numerisk analys)
Department of Chemistry, University of Wisconsin. (The Fredrickson group)
Show others and affiliations
2009 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, Vol. 79, no 14, 144201-1-144201-10 p.Article in journal (Refereed) Published
Abstract [en]

While performing molecular-dynamics simulations of a simple monatomic liquid, we observed the crystallization of a material displaying octagonal symmetry in its simulated diffraction pattern. Inspection of the atomic arrangements in the crystallization product reveals large grains of the beta-Mn structure aligned along a common fourfold axis, with 45° rotations between neighboring grains. These 45° rotations can be traced to the intercession of a second crystalline structure fused epitaxially to the beta-Mn domain surfaces, whose primitive cell has lattice parameters a=b=c=a_{beta-Mn}, alpha =beta =90°, and gamma =45°. This secondary phase adopts a structure which appears to have no known counterpart in the experimental literature, but can be simply derived from the Cr3Si and Al3Zr4 structure types. We used these observations as the basis for an atomistic structural model for octagonal quasicrystals, in which the beta-Mn and the secondary phase structure unit cells serve as square and rhombic tiles (in projection), respectively. Its diffraction pattern down the octagonal axis resembles those experimentally measured. The model is unique in being consistent with high-resolution electron microscopy images showing square and rhombic units with edge-lengths equal to that of the beta-Mn unit cell. Energy minimization of this configuration, using the same pair potential as above, results in an alternative octagonal quasiperiodic structure with the same tiling but a different atomic decoration and diffraction pattern.

Place, publisher, year, edition, pages
Colllege Park, Maryland, USA: American Physical Society , 2009. Vol. 79, no 14, 144201-1-144201-10 p.
Keyword [en]
Crystallisation, electron microscopy, liquid metals, liquid structure, liquid theory, manganese, molecular dynamics method
National Category
Condensed Matter Physics
Research subject
Materials Science
URN: urn:nbn:se:su:diva-27901DOI: 10.1103/PhysRevB.79.144201ISI: 000265943200050OAI: diva2:219798
Available from: 2009-05-28 Created: 2009-05-28 Last updated: 2009-08-10Bibliographically 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

Open Access in DiVA

No full text

Other links

Publisher's full textLink to doctoral thesis

Search in DiVA

By author/editor
Elenius, MånsLidin, Sven
By organisation
Numerical Analysis and Computer Science (NADA) (together with KTH)Department of Inorganic Chemistry
In the same journal
Physical Review B Condensed Matter
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 83 hits
ReferencesLink to record
Permanent link

Direct link