Universal viscosity-equation for silicate melts over wide temperature and pressure ranges

The viscous behavior of melts in the system diopside-anorthite has been studied to find a universal viscosity-equation independent of pressure and composition. esent results suggest that the WLF-equation is appropriate: all viscosity-temperature data of six melts along the diopsideanorthite join over a wide temperature range at 0.1 MPa pressure are plotted on a unified curve in accordance with the WLF-equation. For diopside melts, the equation also works well at high pressures up to 2 GPa; it includes the success of estimation of pressure dependence of the glass-transition temperature (Tg), dTg/dP, using viscosity data both at 0.1 MPa and high pressures. If one has only three constants; Tg at 0.1 MPa, the viscosity at Tg and the dT/gdP value, it is possible to estimate not only the viscosity-temperature relation but also the pressure dependence for these melts. nfigurational entropy theory provides a theoretical background for the WLF-equation in interpreting aspects of the viscous behavior of these melts.