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Evidence for a liquid-solid critical point in a simple monatomic system
Stockholms universitet, Naturvetenskapliga fakulteten, Numerisk analys och datalogi (NADA), (tills m KTH).
Dept. of Materials Science and Engineering, Royal Institute of Technology.
2009 (engelsk)Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 131, nr 104502Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

It is commonly believed that the transition line  separating a liquid and a solid cannot be interrupted by a  critical point. This opinion is based on the traditional  symmetry argument that an isotropic liquid cannot be  continuously transformed into a crystal with a discrete  rotational and translational symmetry. We present here a  molecular-dynamics simulation of a simple monatomic system  suggesting the existence of a liquid-solid spinodal terminating  at a critical point. We show that, in the critical region, the  isotropic liquid continuously transforms into a phase with a  mesoscopic order similar to that of the smectic liquid  crystals. We argue that the existence of both the spinodal and  the critical point can be explained by the close structural  proximity between the mesophase and the crystal. This indicates  a possibility of finding a similar thermodynamic behaviour in  gelating colloids, liquid crystals and polymers.

sted, utgiver, år, opplag, sider
2009. Vol. 131, nr 104502
Emneord [en]
Critical point, Spinodal, phase transition
HSV kategori
Forskningsprogram
materialvetenskap
Identifikatorer
URN: urn:nbn:se:su:diva-29017DOI: 10.1063/1.3213616OAI: oai:DiVA.org:su-29017DiVA, id: diva2:228576
Tilgjengelig fra: 2009-08-04 Laget: 2009-08-04 Sist oppdatert: 2017-12-13bibliografisk kontrollert
Inngår i avhandling
1. Computer Simulations of Simple Liquids with Tetrahedral Local Order: the Supercooled Liquid, Solids and Phase Transitions
Åpne denne publikasjonen i ny fane eller vindu >>Computer Simulations of Simple Liquids with Tetrahedral Local Order: the Supercooled Liquid, Solids and Phase Transitions
2009 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: Numerical Analysis and Computer Science (NADA) (together with KTH), Stockholm University, 2009. s. vi, 65
Serie
Trita-CSC-A, ISSN 1653-5723 ; 2009:14
Emneord
Simple liquids, glasses, liquid-glass transition, supercooled liquids, tetrahedral liquids, phase transitions, quasicrystals, molecular dynamics
HSV kategori
Forskningsprogram
numerisk analys
Identifikatorer
urn:nbn:se:su:diva-27876 (URN)978-91-7155-901-2 (ISBN)
Disputas
2009-09-11, Sydvästra galleriet, Biblioteket, Kungl Tekniska Högskolan, Osquars backe 25, Stockholm, 10:15 (engelsk)
Opponent
Veileder
Merknad
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. Tilgjengelig fra: 2009-08-20 Laget: 2009-05-27 Sist oppdatert: 2009-08-27bibliografisk kontrollert

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Totalt: 251 treff
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