Viscosity, relaxation time, glass temperature, melting temperature and fragile-to-strong transition parameterizations at extreme pressures in soft-matter systems

摘要

This contribution presents the extended, pressure-related Vogel-Fulcher-Tammann equation applied to portray the pressure evolution of viscosity η(P) and the related dynamic properties, such as the primary relaxation time τ(P), in soft-matter systems as well as the modified Simon-Glatzel-type equation for describing pressure dependences of the glass temperature T_g(P), the melting temperature T_m(P) and the fragile-to-strong dynamical transition in confined water T_d(P). Both equations are capable of penetrating the negative pressure (isotropically stretched liquid) domain, and at very high pressures are capable of the inverse behavior. They have the following forms: (i) η(P) = η0 exp[D_PΔP/(p_0 - P)] = η0 exp[(D_P - D_PP_(SL))/(P_0 - P)], where P_0 is the estimate of the ideal glass temperature, P_(SL) is for the stability limit at negative pressures and D_P denotes the pressure fragility strength coefficient and (ii) T_(g,m,d)(P) = (T_(g,m,d))~0(1 + (P - (P_(g,m,d)~0/(π + (P_(g,m,d)~0))) exp(-(P - (P_(g,m,d))~0)/c), where (T_(g,m,d))~0 and (P_(g,m,d))~0 are the reference temperature and pressure, -π is the negative pressure asymptote and c is the damping coefficient responsible for the inversion phenomenon.