A novel liquid–liquid phase transition has been investigated for a wide variety of pure substances, including water, silica and silicon. From computer simulations using the Stillinger–Weber (SW) classical empirical potential, Sastry and Angell1 demonstrated a first order liquid–liquid transition in supercooled silicon at zero pressure, supported by subsequent experimental and simulation studies. Whether the line of such first order transitions will terminate at a critical point, expected to lie at negative pressures, is presently a matter of debate2. Here we report evidence for a liquid–liquid critical point at negative pressures, from computer simulations using the SW potential. We identify Tc∼1,120±12 K, Pc∼−0.60±0.15 GPa as the critical temperature and pressure. We construct the phase diagram of supercooled silicon, which reveals the interconnection between thermodynamic anomalies and the phase behaviour of the system as suggested in previous works3,4,5,6,7,8,9,10. We also observe a strong relationship between local geometry (quantified by the coordination number) and diffusivity, both of which change dramatically with decreasing temperature and pressure.
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We wish to thank C. A. Angell, P. G. Debenedetti, N. Jakse, K. F. Kelton, P. H. Poole, F. Sciortino, F. Spapen, H. E. Stanley, F. Starr, H. Tanaka and M. Widom for many fruitful discussions and comments on the manuscript. We thank CCMS, JNCASR for the computing facilities, and the Department of Science and Technology, India for support. S. Sastry is adjunct faculty at the International Centre for Theoretical Sciences, TIFR.
The authors declare no competing financial interests.
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Vasisht, V., Saw, S. & Sastry, S. Liquid–liquid critical point in supercooled silicon. Nature Phys 7, 549–553 (2011). https://doi.org/10.1038/nphys1993
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