The different aspects of liquid state behavior currently in focus are classified in terms of their place in the range of ralaxation times separating the microscopic (phonon) time from the structural relaxation time at the normal glass transition Tg. The place within this scheme of each of the contributions to this symposium is identified. Special attention is given to the crossover between "free diffusion" and "landscape-dominated" regimes. Thermodynamic estimates of the "height of the landscape" are given for strong and fragile liquids and a correspondence is found between the thermodynamic estimate and characteristic temperatures Tc of mode coupling theory and Tx of Rössler scaling obtained from different analyses of the dynamic properties. Fragile liquids have all their configurational microstates (configurons) packed into a small energy band between kTK and the upper limit at kTu i.e. Tu is relatively close to TK. In the landscape-dominated regime, clustering occurs. We outline a cooperative cluster model which can generate high fragility and which in extreme cases can provoke a first-order phase transition to the fully clustered state.
ASJC Scopus subject areas
- Chemical Engineering(all)