1. 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

2.  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

3. 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?

4. 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

5.  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

6. 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

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

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

9. 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

10. 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

11. 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

13. Anomaly in melting curve as a function of pressure water, Si, Ge, Cs, Ba, Eu

14.  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

15. A. Scala et. al., J. Statistical Physics 100, 97 (2000)

17.  Possibility of synthesizing superstable metallic glasses  Mechanism of forming superstable metallic glasses

18. 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

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