Fragility under pressure

Abstract

Viscosities of the fragile glass-forming liquids ortho-terphenyl and salol have been measured in a diamond anvil cell for pressures up to 1 GPa and for temperatures 300 K < T < 425 K. Utilizing a rolling ball technique viscosities up to 10^8 mPas could be determined. From these data the pressure dependence of the fragility index, corresponding to a reference viscosity of about 10^8 mPas, has been calculated. For ortho-terphenyl it is found that this "low-viscosity" fragility index is pressure invariant within experimental error. Salol exhibits a more complicated behavior