Phase separation kinetics in Two Temperature Induced Phase Separation(2-TIPS)

Two Temperature Induced Phase Separation (2-TIPS) describes the phase separation in mixtures of active and passive particles, modeled using scalar activity. In scalar models, particle activity is proportional to their temperature, with the relative temperature difference between “hot” and “cold” particles defined as activity (χ). Our molecular dynamics (MD) simulations show that the hot and cold particles phase separate when χ exceeds a density-dependent critical value.

We investigate kinetics in 2-TIPS using MD and coarse-grained modeling in 3D and 2D. The coarse-grained model couples two passive Model B equations for hot and cold particles, with coupling terms emulating the energy transfer between them by raising the temperature of cold particles and lowering that of hot particles.

MD simulations reveal that phase separation begins immediately after the quench at high densities, forming bi-continuous domains rich in hot or cold particles. These interconnected domains are also observed in the coarse-grained model for the mixture’s critical composition. Both MD and coarse-grained models show dynamic scaling of the correlation function, indicating self-similar domain growth and algebraic growth in domain length with a growth exponent of 1/3, known as the Lifshitz-Slyozov exponent, widely observed in passive systems. Thus, our results demonstrates that the universality of phase separation kinetics extends to non-equilibrium binary mixtures, beyond the scope of equilibrium systems.