Limiting Tensions For Liquids and Glasses from Laboratory and MD Studies

Abstract

We discuss first the systematic passage of liquids from states of positive pressure to states of isotropic tension, using spectroscopic characterization methods. We then describe some experimental methods for characterizing the range of temperature under which common liquids and glassformers can be studied in such negative pressure states. While rather large tensions, up to nearly 200MPa have been obtained in these laboratory studies, much larger tensions can be generated in systems with long range attractive forces. We characterize the limiting tensions for such cases using the methods of molecular dynamics. In practice, liquids fail by homogeneously nucleated cavitation at tensions far below the spinodal limits defined by equations of state. We anticipate a crossover from nucleated to spinodal failure as the glass transition temperature meets the spinodal. We lay the basis for the experimental testing of this notion, using laboratory data for the case of the model glassformer, o-terphenyl. In the case of SiO₂ glass we are able to characterize the failure mechanism.