A computational investigation of the thermodynamics of the Stillinger-Weber family of models at supercooled conditions

Abstract

The existence of metastable liquid-liquid phase transitions (LLPTs) in tetrahedral liquids such as water, silicon, and silica has been the subject of vigorous scientific debate. Because high crystallization rates hinder experimental investigation at deeply supercooled conditions, computer simulation has been widely employed to investigate the existence of LLPTs in molecular models of tetrahedral liquids. The Stillinger-Weber (SW) model of silicon (and more generally, the SW family of models) has been actively studied along these lines. Whereas some studies observe evidence of an LLPT in this model, others report that only a single metastable liquid exists under deeply supercooled conditions. Here, we perform extensive state-of-the-art free energy calculations to investigate the possibility of an LLPT in the SW model of silicon. A similar analysis is also presented for the generalized SW family of models constructed by varying the strength of the three-body energetic term. Our analysis does not show any evidence of an LLPT in SW silicon nor in the generalized family of SW models over the parameter ranges studied. Explanations for the aforementioned discrepancies between previous studies are provided, along with explicit demonstrations of how these discrepancies may have occurred. Outstanding ambiguities and directions for future work are also discussed.

GRAPHICAL ABSTRACT

KEYWORDS:

• Liquid-liquid transition
• silicon
• tetrahedral liquids

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

P.G.D. gratefully acknowledges the National Science Foundation, Division of Chemistry (Grant CHE-1213343) and Division of Chemical, Bioengineering, Environmental, and Transport Systems (Grant CBET-1263565), for support for early aspects of this work. J.C.P. acknowledges support from the Welch Foundation (Grant E-1882). S.S. gratefully acknowledges support through the J.C. Bose fellowship, Science and Engineering Research Board (SERB), DST, India.