Unusual phase behaviour in one- component systems with isotropic interactions Limei Xu WPI-AIMR, Tohoku University, Japan WPI-AIMR, Tohoku 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

 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. Motivation Similar phase behaviors shared by very different materials

Questions 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 simulation Number 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 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 Diagram

compressibility T W (P) Pc=0.24 P<P c : No anomalous behaviour! (Metastability ) P>P c : Response functions show peaks. The location of the peaks decreases approaching to the critical pressure Changes in thermodynamics upon crossing widom line

Perfect Crystal: Q 6 =0.57; Random configuration: Q 6 =0.28 Orientational order parameter : Changes in structures upon crossing Widom line

Two glass states obtained upon cooling LDL  LDA HDL  HDA Two glass states upon cooling: HDA and LDA

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 Polyamorphism

L. Xu, S. V. Buldyrev, N. Giovambattista, C. A. Angell H. E. Stanley, JCP (2009) HDL-LDA glass transition and liquid-liquid phase transition Detection of glass transition: thermal expansion

HDL-HDA glass transition and liquid-liquid phase transition 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 Cp The 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. Conclusions

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 T W P<Pc: Upon crossing coexistence line, No kink in D TWTW Pc=0.24 Changes in dynamics upon crossing Widom line

HDL-like LDL-like T Widom Translational order parameter: Random configuration: t=0