Correlation between dynamic fragility and glass transition temperature for different classes of glass forming liquids

Here we compile literature data for dynamic fragility m for six types of glass forming liquids: polymers, small molecule organics, hydrogen bonding organics, inorganics, ionic and metallic glass formers. Our analysis of the data shows that different categories of glass forming liquids exhibit different behaviors in terms of the correlation between m and T_g, a correlation not previously examined. For example, for hydrogen bonding organics, polymeric and metallic glass formers, there is an approximately linear increase in m with increasing T_g. While for inorganic glass formers, m appears almost independent of T_g, remaining nearly constant over a wide range in T_g. At the same time, another important parameter, the apparent activation energy E_g at T_g has been investigated. It was found that E_g increases with T_g to the 2nd power for hydrogen bonding organics, polymeric and metallic glass forming liquids, while E_g of inorganic glasses has a linear dependence on T_g.