The fragility of liquids and colloids and its relation to the softness of the potential.

A parameter that is often used to characterize the dynamics of supercooled liquids is the dynamic fragility, however it is still debated how the fragility is related to other physical properties. Recent experimental data on colloidal systems have found that fragility decreases with increasing softness of the intermolecular potential. This result is in apparent disagreement with recent molecular dynamics simulations reporting the opposite behavior. Herein, using the thermodynamical scaling exponent γ as a measure of the steepness of the potential we show how these different results can be reconciled and also agree with previous results obtained for the dynamics of supercooled liquids at high pressures.