(189bp) Thermodynamic Description of Shear-Induced Phase Transition in Jammed Soft Particle Glasses

Recently we computationally showed that jammed suspensions of soft particles can undergo a phase transition under steady (Khabaz et al. Phys. Rev. Fluids. 2, 093301 (2017)) and oscillatory (Khabaz et al. Phys. Rev. Fluids. 3, 033301 (2018)) shear flows and form variety of ordered microstructures. In particular using the three-dimensional particle-dynamics simulation, we demonstrated that polydisperse suspensions formed a layered microstructure parallel to the flow-vorticity plane at high shear rates. The formation of the layered microstructure significantly decreases the internal energy and entropy of the system. Although the thermal forces are negligible in our model for jammed suspensions of soft particles due to the significance of the elastic forces between particles at contact, we can define an effective temperature using the excess entropy and elastic energy of the system. Rosenfeld theory, which connects the excess entropy to the microstructure of a system, is employed to quantify the excess entropy of the glassy and layered suspensions under different shear rates and volume fractions. Our results at a given shear rate show that the temperature and Helmholtz free energy of the layered microstructure is lower than that of the glassy suspensions. Both temperature and Helmholtz free energy follow a similar trend as the flow curve of these materials, i.e. an increase in the shear rate in each state increases the temperature and elastic energy of the suspension. In addition, the defined temperature exhibits an approximately linear relationship with the shear stress and elastic energy, which indicates that in a jammed state of these soft suspensions the shear stress can play the temperature role.