Atreyee Banerjee

Data-driven identication of Glass Transition Temperature in Polymer Melts

On cooling, the dynamical properties of many polymer melts slow down exponentially, leading to a glassy state without any drastic change in static structure. We propose a data-driven approach, which utilises the high-resolution details accessible through the molecular dynamics simulation and considers the structural information of individual chains. It clearly identifies the glass transition temperature of polymer melts of semiflexible chains. By combining principal component analysis (PCA) and clustering, we identify glass transition temperature at the asymptotic limit even from relatively short-time trajectories. We demonstrate that fluctuations captured by the principal component analysis reflect the change in a chain's behaviour: from conformational rearrangement above to small vibrations below the glass transition temperature. We demonstrate the generality of the approach by using different dimensionality reduction and clustering approaches. The method can be applied to a wide range of systems with microscopic/atomistic information. More recently we applied this methodology to all-atom acrylic paint systems. Our study reveals the explicit role of backbone and side chain residues to determine the glass transition temperature.

Characterisation of the Free Energy Landscapes of Polymeric Polymorphs using data driven methods

The higher dimensional the free energy landscapes (FELs) are often expressed in terms of essential degrees of freedom known as collective variables (CVs). Data-driven techniques provide a systematic route to construct the free energy landscape without the need for extensive a priori intuition about the system. We are looking at the polymorphic transitions of polymer melts using data driven methods to overcome the two main problems: identifying goods CVs and the inherent longer timescales of the transitions.

Connecting thermodymanics to the dynamical properties of supercooled liquids

In liquid state theory, there is a well-known connection between dynamical and structural properties. However, glass-forming systems such as the Kob-Andersen model with interactions described by Lennard-Jones (LJ) and Weeks-Chandler-Andersen (WCA) potentials exhibit seemingly similar structural properties and entirely different dynamical behaviour. Earlier we have shown that this difference in dynamics is orgininated from a thermodynamical quantity. Now, we use the Kirkwood-Buff solution theory to compute thermodynamic quantities which are related to the microscopic structure of the systems.