Over the last few decades, computational science has extended the range of phenomena that can be investiagted in the framework of Physics. Computer simulations can complement experiments in the search of an understanding of fundamental processes in nature. We use classical molecular simulations to study the underlying Physics manifested in many of the intruiging phenomena in soft matter. It includes phase behaviour, non-equilibrium behaviour and response to inhomogenous conditions of soft materials ranging from colloidal supensions to polymers and surfactants. Such materials show complex structure, dynamics and response on a wide range of length scales from nanoscopic to microscopic, resulting in a wide range of functionality and applications. Few of the current research directions are listed below.
The interactions between charged colloidal particles in solution can be complex and varied. One particularly interesting case is when the particles attract one another at small separations, but repel at larger separations. These competing interactions lead to very rich phase behavior in these systems like formation of cluster fluids. Our investigations on a highly size-asymmetric binary colloidal mixtures shows that counter ion distributions around the colloidal particles are nonlinear and this leads to highly non-additive interactions between the two components. In such an asymmetric mixture, even though likely charged, larger colloidal particles form a cluster fluid which is in very good agreement with experimental findings. Similar effects may be observed in the case highly charge-asymmetric mixtures also. We are investigating the effect of this charge/size polydispersity in colloidal mixtures on phase behavior and dynamical properties using classical molecular simulation methods such as Monte Carlo and molecular dynamics.
( in colloboration with Dr. J. Horbach, DLR, Koln, Germany )
The analysis of the behaviour of complex systems in external fields or non-equilibrium conditions may shed additional light on many features of the structural and dynamical properties of these systems. Non-equilibrium conditions can also give rise to many interesting phenomena - for example, shear thinning and thickening transitions etc.. We carry out non-equilibirum molecular dynamics simulations to investigate the behaviour of these systems under inhomogenous conditions like the flow behaviour in a temperature gradient.