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High temperature viscosity limit of silicate melts with least fitting error
Lei Gan, Yihong Zhou and Lina Jiao
The high temperature viscosity limits (log η∞) implied by various three-variable non-Arrhenian viscosity models were investigated, by fitting each model to 4728 high quality viscosity data representing 336 silicate melts. The models used a global optimization algorithm. It indicates it is reasonable to treat the log η∞ as a composition-independent constant, because the log η∞ values obtained by free fitting show no clear trend as function of compositions. For each form of temperature dependent equation, a bestfitting log η∞ value with lowest fitting error can be found, which is different from the average log η∞ value. The best-fitting values are –3.52, –1.06, –2.65 and –2.02 log Pa·s for Vogel-Fulcher-Tammann (VFT), Avramov- Milchev (AM), Adam-Gibbs (AG) and Mauro-Yue-Ellison-Gupta-Allan (MYEGA) equations, respectively. A viscosity model can be significantly simplified and meanwhile ensures an acceptable high accuracy by setting log η∞ as derived best-fitting value.
Keywords: Silicate melt, high temperature viscosity limit, non-Arrhenian equations, constrained fitting, best fitting, viscosity model