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Center for Nonlinear Studies |
Tetrahedral liquids are liquids in which the interaction prefers tetrahedral symmetry. Water (H2O), pure Silicon(Si) and Carbon(C) are examples of tetrahedral liquids that are extremely important in nature and applications. These materials show interesting thermodynamic behavior when cooled (e.g., the density anomaly, and increase in specific heat near freezing). In recent years it has been proposed that tetrahedral liquids can have more than one liquid phase, although this is still controversial. We suggest a statistical mechanics theory for a set of coarse-grained variables that we derive using the widely used Stillinger-Weber potential (one of the models used in simulations of Silicon). Our theory manages to describe the temperature dependent structural changes that have been observed in molecular dynamics simulations using the Stillinger Weber potential. This framework suggests, but does not explicitly exhibit, a mechanism for the liquid-liquid phase transition. Whether a modification of this coarse-grained theory can self-consistently describe a liquid-liquid phase-transition is a matter of continuing research.
Host: Peter Loxley, loxley@lanl.gov