CONSTRAINTS, METASTABILITY, AND INHERENT STRUCTURES IN LIQUIDS

Void-size distributions have been calculated for the shifted-force Len nard-Jones fluid over substantial temperature and density ranges, both for the liquid-state configurations themselves, as well as for their inherent structures (local potential energy minima). The latter distri bution is far more structured than the former, displaying fee-like sho rt-range order, and a large-void tail due to system-spanning cavities. Either void distribution can serve as the basis for constraints that retain the liquid in metastable states of superheating or stretching b y eliminating configurations that contain voids beyond an adjustable c utoff size. While acceptable cutoff sizes differ substantially in the two versions, ranges of choices have been identified yielding metastab le equations of state that agree between the two approaches. Our resul ts suggest that the structure-magnifying character of configuration ma pping to inherent structures may be a useful theoretical and computati onal tool to identify the low-temperature mechanisms through which liq uids and glasses lose their mechanical strength.