Inter-basin fluctuations in glass-forming liquids: short time and long time thermodynamic susceptibilities

Thermodynamic effects of local structure fluctuations in glassformers are analyzed in terms of energy basins and inter-basin hopping. Depending on the time-scale of measurement, one observes short-time thermodynamic properties related to a narrow set of basins, or equilibrium properties that include structural relaxation. The inter-basin hopping is manifested by the fluctuations of the pressure, internal energy, and other thermodynamic short time characteristics. Formulas relating the inter-basin fluctuations of pressure and internal energy to the differences between the long- and short-time susceptibilities are found. Based on obtained relations, we discuss the relative sensitivity of the structure to temperature and pressure.