Methodwaveletformultifractalimageanalisis Anisotropic Isotropic
Unusual phase behaviour in one-component systems with isotropic interactions
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Unusual phase behaviour in one- component systems with isotropic interactions Limei Xu Limei Xu WPI-AIMR, Tohoku WPI-AIMR, Tohoku University, Japan University, Japan In collaboration with: C. A. Angell Arizona State University S. V. Buldyrev Yeshiva University N. Giovambattista New York Brookline college H. E. Stanley Boston University M. Tokuyama Tohoku university
description
Limei Xu WPI-AIMR, Tohoku University, Japan. Unusual phase behaviour in one-component systems with isotropic interactions. In collaboration with: C. A. Angell Arizona State University S. V. Buldyrev Yeshiva University N. Giovambattista New York Brookline college - PowerPoint PPT Presentation
Transcript of Unusual phase behaviour in one-component systems with isotropic interactions
Unusual phase behaviour in one-component systems with isotropic interactions
Limei Xu Limei Xu WPI-AIMR, Tohoku University, JapanWPI-AIMR, Tohoku University, Japan
In collaboration with: C. A. Angell Arizona State UniversityS. V. Buldyrev Yeshiva UniversityN. Giovambattista New York Brookline collegeH. E. Stanley Boston UniversityM. Tokuyama Tohoku university
Liquid-liquid phase transition: Tetrahedral structured systems: water, Si, Ge, SiO2, BeF2 Metallic system, such as Y3Al5O12
Polyamorphism (amorphous-amorphous transition under pressure)
Tetrahedral structured systems: water, Ge Metallic system: Ce55Al45
Both liquid transitions and polyamorphism, although caused in different materials by different chemical properties, have similar physics: involving two local structures, with one having large open spaces between particles that collapse under pressure.
MotivationMotivation
Similar phase behaviors shared by very different materials
Questions we askQuestions we ask
Universal model that determine whether these features and phenomena are related or exist independently
How we can guide experimentalists to search for new materials with better performance?
E. A. Jagla, J. Chem. Phys. 111, 8980 (1999)L. Xu et.al. Phys. Rev. E (2006)
MD simulationNumber of particles: N=1728
Effective potential of water at T=280K
T. Head-Gordon and F. H. Stilinger. J. Chem. Phys. 98, 3313 (1993)
U( r ) ~ ln g ( r )
Two-scale isotropic interaction potentialsTwo-scale isotropic interaction potentials
Stable liquid-liquid critical point (LLCP)
Negative sloped melting line
LDA and HDA
L. Xu, S. V. Buldyrev, C. A. Angell, H. E. Stanley, Phys. Rev. E (2006)L. Xu, P. Kumar, S. V. Buldyrev, P. H. Poole, F. Sciortino, S.-H Chen, H. E. Stanley, PNAS (2005)
Widom line
Phase DiagramPhase Diagram
compressibility
TW(P)
Pc=0.24
P<Pc : No anomalous behaviour! (Metastability) P>Pc : Response functions show peaks. The location of
the peaks decreases approaching to the critical pressure
Changes in thermodynamics upon crossing Changes in thermodynamics upon crossing widom linewidom line
Perfect Crystal: Q6=0.57; Random configuration: Q6=0.28
Orientational order parameter:
Changes in structures upon crossing Widom Changes in structures upon crossing Widom lineline
Two glass states obtained upon cooling LDL LDA HDL HDA
Two glass states upon cooling: HDA and Two glass states upon cooling: HDA and LDALDA
L. Xu, S. V. Buldyrev, H. E. Stanley, M. Tokuyama (in preparition)
System with LLCP: approach of new high density glasses by compression and decompression along constant pressure
PolyamorphismPolyamorphism
L. Xu, S. V. Buldyrev, N. Giovambattista, C. A. Angell H. E. Stanley, JCP (2009)
HDL-LDA glass transition and liquid-liquid phase HDL-LDA glass transition and liquid-liquid phase transitiontransition
Detection of glass transition: thermal expansion
HDL-HDA glass transition and liquid-liquid phase HDL-HDA glass transition and liquid-liquid phase transitiontransition
L. Xu, S. V. Buldyrev, N. Giovambattista, C. A. Angell H. E. Stanley, JCP (2009)
H=U+PV
Detection of glass transition: thermal expansion or CpThe second approach is more pronounced, indicating that: Glass transition is the onset of the kinetics, while liquid-liquid Phase transition is the onset of the volume/density change
Anomaly in melting curve as a function of pressure water, Si, Ge, Cs, Ba, Eu
Simple two-scale potential shows rich phase behavior: LLPT and polyamorphism
Near the critical point, response functions (thermodynamic and structural) show maxima upon crossing the Widom line, thus provide a way for experiments to locate the possible liquid-liquid critical point
The model tells us how to distinguish glass transition from the Widom line associated with the liquid-liquid phase transition.
Our study indicates an alternative way to make glasses via polyamorphism.
ConclusionsConclusions
A. Scala et. al., J. Statistical Physics 100, 97 (2000)
Possibility of synthesizing superstable metallic glasses
Mechanism of forming superstable metallic glasses
P>Pc: Upon crossover the Widom line, a kink in D occurs near TW
P<Pc: Upon crossing coexistence line, No kink in D
TW
Pc=0.24
Changes in dynamics upon crossing Widom Changes in dynamics upon crossing Widom lineline
HDL-like
LDL-like
TWidom
Translational order parameter:
Random configuration: t=0
