Prof. Nisanth N. Nair

Department of Chemistry

Indian Institute of Technology Kanpur

E-mail id:nnair[at]iitk.ac.in

 

Brief Bio-sketch:

Dr. Nisanth N. Nair currently holds the position of Professor at the Department of Chemistry, Indian Institute of Technology Kanpur (IIT Kanpur). He joined IIT Kanpur in 2008 (Dec.) after his four years of post-doctoral work with Prof. Dominik Marx, Ruhr-University, Bochum (Germany). His research interests include development of computational methods for free energy calculations, QM/MM computations, and hybrid DFT based ab initio MD simulations. He also works in modelling enzymatic reactions, catalytic reactions in zeolites, homogenous catalytic reactions, and reactions on polymer and solid surfaces.

ENHANCED SAMPLING AND FREE ENERGY CALCULATIONS USING MOLECULAR DYNAMICS WITH HYBRID DENSITY FUNCTIONALS AND PLANE WAVES

Plane wave basis sets offer many advantages in ab initio molecular dynamics (AIMD) due to their efficiency and simplicity. In combination with hybrid functionals, they become computationally expensive due to the evaluation of the Hartree-Fock exchange energy. The computational cost can be significantly reduced by screening the Kohn-Sham orbital products after localizing the orbitals in real space. However, such a procedure introduces apparent errors in the wavefunctions and nuclear forces resulting in unstable dynamics. We overcome this problem by introducing a noise-stabilized AIMD algorithm which can stabilize the dynamics in the presence of noisy forces and also permits to use insufficiently converged wavefunctions. This approach combined with rare event sampling methods enable us to perform several hundreds of picoseconds of AIMD trajectory at the level of hybrid DFT and compute free energies of chemical reactions in systems containing hundreds of atoms. The results provide insights into the error of the Perdew-Burke-Ernzerhof functional in predicting the free energy barrier for hydrolysis reactions in water.

 

References :

S. Mondal, J. Debnath, B. Meyer, and N. N. Nair, J. Chem. Phys. 149, 144113 (2018).