Activation force dependence of the fluidization transition in supercooled active water

Abstract

Using an activation model reproducing facilitation mechanisms, we found recently a fluidization transition in supercooled water triggered by the motion of a few active molecules. We investigate here the effect of the activation force on the transition. The activation force increases the probability for active molecules to overcome the energy barrier induced by caging. The induced molecular motions result in an intermittent loose structure leading to a decrease of energy barriers around the moving molecule, thus facilitating the motion of nearby molecules. Therefore we expect the force, if small enough, to increase the facilitation mechanism, and as a result cooperative motions induced by it. As a result the activation force permits to tune facilitation and cooperative motions in active glass-formers. We find an optimum force for cooperative motions that we evaluate to be around 3.5pN, a value in the range of protein motor forces. As expected for a phase transition we observe peaks of cooperative motions (dynamic heterogeneity) on the transition. This result shows that dynamical heterogeneity are the cooperative motions of physical importance for the transition.