Some novel states of colloidal matter: modulated liquid, modulated crystal and glass

East tunability of interparticle interactions makes aqueous suspensions of charged polystyrene spheres idea; systems for understanding freezing of liquids to crystal and glass. This review will cover two aspects of our recent work: (i) Density functional theory and Monte-Carlo simulations of the phase diagram and the order of the modulated liquid to crystal transition in laser field modulated colloids. We show that for sufficient strength of the modulating potential ßVe, the freezing transition changes from first order to a continuous transition. Our simulations reveal a novel reentrant laser-induced melting transition from the crystal to the modulating liquid phase with increasing βVe. (ii) Brownian dynamics simulations on binary colloids to study structural evolution and dynamics as liquid freezes into a crystal (at low volume fraction φ) or into a glass (at high φ). The two- and four-point density autocorrelation functions show that there is no growing correlation length near the glass transition. The bond-orientational order is characterised in terms of quadratic rotational invariants and bond-orientational correlation functions. The temperature-dependence of average relaxation times extracted from the stretched exponential fit to correlation functions obey the Vogel-Tammann-Fulcher law. The van-Hove correlation functions and the subdiffusive behaviour of the mean-squared displacements reveal strongly cooperative particle motion near the glassy state.