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