The structural difference between strong and fragile liquids

A structural order parameter for disordered configurations is defined, based, not on local topologies, but the degree of restraint imposed each atom. This provides a clear distinction between strong liquid (SiO2) and fragile (a binary Lennard-Jones mixture) without reference to dynamics. Where exhibits an abrupt transition from unrestrained restrain below melting point, molten silica highly constrained even at equilibrium. We determine temperature dependence average number particles restrained per pinned particle consider feature potential energy landscape responsible determining fragility.