On the glass temperature under extreme pressures

The application of a modified Simon-Glatzel-type relation [Z. Anorg. Allg. Chem. 178, 309 (1929)] for the pressure evolution of the glass temperature is presented, namely, $Tg(P)=Tg0[1+ΔP∕(π+Pg0)]1∕bexp[−(ΔP∕c)]$⁠, where $(Tg0,Pg0)$ are the reference temperature and pressure, $ΔP=P−Pg0$⁠, $−π$ is the negative pressure asymptote, $b$ is the power exponent, and $c$ is the damping pressure coefficient. The discussion is based on the experimental $Tg(P)$ data for magmatic silicate melt albite, polymeric liquid crystal P8, and glycerol. The latter data are taken from Cook et al. [J. Chem. Phys. 100, 5178 (1994)] and from the authors’ dielectric relaxation time $(τ(P))$ measurements, which employs the novel pressure counterpart of the Vogel-Fulcher-Tammann equation: $τ(P)=τ0Pexp[DPΔP∕(P0−P)]$⁠, where $ΔP=P−PSL$ (⁠$PSL$ is the stability limit hidden under negative pressure), $P0$ is the estimation of the ideal glass pressure, and $DP$ is the isothermal fragility strength coefficient. Results obtained suggest the hypothetical maximum of the $Tg(P)$ curve, which can be estimated due to the application of the supporting derivative-based analysis. A hypothetical common description of glass formers characterized by $dTg∕dP>0$ and $dTg∕dP<0$ coefficients is suggested. Finally, the hypothetical link between molecular and colloidal glass formers is recalled.