Accurate Computation and Efficient Exploration of High Dimensional Free Energy Landscapes of Chemical Reactions

Exploration and computation of free energy surfaces of chemical reactions are pivotal to computationally predict reaction mechanisms, reaction pathways, and kinetics. Computing free energy surfaces of complex reactions, especially in soft matter system, requires advanced molecular dynamics (MD) simulation techniques. Although, tremendous progress has been made in the recent years in this direction, several limitations are yet to be addressed to make the computations efficient and more accurate. Over the past few years, my group has put forward a number of new methods to address the outstanding challenges. In my talk, I will be presenting two of our recent contributions. A new sampling technique called Temperature Accelerated Sliced Sampling (TASS) has been developed to explore high dimensional free energy surfaces of complex chemical reactions. TASS outperforms other conventional methods in sampling efficiency and convergence of free energy estimates. In order to carryout MD simulations at a higher level of density functional theory, beyond the widely used GGA level of theory, we have made a new implementation of hybrid-exact exchange integrals with plane-wave basis set in the CPMD program. Together with a noise-stabilized MD algorithm, this implementation has enabled us to perform highly accurate free energy calculations at a much lower computational cost.