Dr. Kalishankar Bhattacharyya

Welcome to the Computational Material Chemistry (CMC) Lab located in the Department of Chemistry at the Indian Institute of Technology, Guwahati (IIT-G). Our research focuses on investigating the computational methods and applications to material science, particularly in energy conversion and storage. Computational electrocatalysis is a particular area of interest. We employ first-principles methods with atomistic modelling to study electronic structure and energetics to advance existing and finding new materials.

Currently, we are actively seeking graduate, and postdoctoral scholars , as well as project students to join our group. Please feel free to reach out to us if you're interested!

KB

Research

Heterogeneous electrocatalysis

One of the major challenges in electrocatalysis that first- principle DFT calculations face at present time are (i) description of the potential dependence of the electrochemical reactions, and (ii) description of the surface structures of the catalysts in solution phase considering the continuous changes of charges and protonated states. We developed a new computational methodology based on the explicit consideration of electrochemical potential and taking account the effects from pH to investigate the electrochemical reactions at transition metal oxide electrocatalyst that are important for fuel cell applications. Here, we extensively employed two fundamental aspects, i.e. (i) description of the redox and acid-base reaction electrochemically, (ii) constant potential approach to understand the reaction mechanisms in electrocatalytic conditions. We are able to reproduce the experimental trends based on this simple and computationally affordable methodology.

Inverted singlet-triplet gap in thermally activated delayed fluorescence materials

Organic molecules have unlimited potential as functional materials due to the enormous diversity in chemical structures and molecular conformations. Yet, electronic and optical properties of organic photo functional molecules have significantly remained unexplored. Thermally activated delayed fluorescence (TADF), a new optoelectronic property, has recently opened an active organic electronics research area. TADF has unique capabilities to harvest triplet exciton through the reverse intersystem crossing (T1→S1) process depending on the singlet-triplet gap. It could directly affect their properties and performances, which is attractive for many low‐cost optoelectronic devices. Recent experimental reports have shown potential TADF applications for a set of closed-shell organic chromophores (cyclazine and heptazine derivative), where first excited singlet (S1) states are lower than first excited triplet (T1) states (ΔEST 0). Due to the violation of Hund's rule, it is thought that the triangular topology of these organic chromophores could undoubtedly play a role in their electronic structures. In the first paper (CPL, 2021, 779, 138827), I have reported a detailed analysis of this unusual electronic structure properties and inabilities to capture the inverted singlet-triplet gap by linear-response TDDFT method. Instead, DLPNO-STEOM-CCSD method can accurately capture this inverted singlet-triplet gap. From the analysis of the DLPNO- STEOM-CCSD results, we found that missing of doubles correlation in the DFT functional is the reason for failure. Hence, we further extended this work where we addressed the inclusion of doubles-corrected TDDFT with proper choice of double- hybrid functional could also capture the inverted singlet-triplet gap from LR-TDDFT.

Singlet fission process in organic molecules

Understanding the electronic coupling and associated pathway in the molecular level is the fundamental to envisage the energy transfer process for light harvesting materials. One aspect of this area is investigating the singlet fission process, which is a splitter of high-energy singlet excited state into two low-energy triplet states, generating one extra exciton per absorbed photon in organic materials. For efficient generations of triplet excition, it has strong dependence on the packing motifs and morphology of chromophores. Identification of exciton states, calculations of electronic couplings of various aggregated chromophores, and related to the excited state relaxation process require advanced computational models for detailed study. In this research project, we investigated SF mechanism considering the thermodynamic condition, its correlation to the molecular structure, and, finally, developed design principle rules of SF process from the first-principles computation.

Two-dimensional materials for nitrogen activation

we demonstrated that single boron atom doped porous C2N monolayer with high thermal stability up to 800K, can be a potential candidate as metal-free single atom catalyst for efficient N2 fixation under visible light Based on the synergistic effect of σ-donation and π-acceptance, N2 easily activated over the B/C2N surface. Our computation reveals that single B atom doped C2N could effectively reduce N2 to NH3 with a record low onset potential of0.18eV through enzymatic pathways. Moreover, decoration of single B atom on C2N significantly enhances the possibility of visible light absorption, rendering them a promising solar light-driven N2 to NH3 reduction (NRR) catalyst.

Machine learning guided excited state properties simulations

The utilization of machine learning models holds immense promise in advancing the realm of excited-state calculations, primarily through a significant reduction in the number of electronic structure computations required. In this particular endeavor, my main focus revolves around the development of a machine learning model based on excited-state calculations. To achieve this, I will employ various optimization techniques, including simulated annealing, grid search, random search, and finite difference gradient descent algorithm, to tune the hyperparameters. By conducting a comparative analysis of both hyperparameter optimization and training data size, we aim to gain deeper insights into the relationship between the machine learning model and the molecules we seek to model using this approach.

Teaching

CH 101 Chemistry Tutorial

CH 430 Quantum Chemistry

CH 110 Chemistry Laboratory

CH 631 Advanced Quantum Chemistry

Group Members

Anchit Rajib Prasad

B.Tech Project Student

Partha Pratim Borah

PhD Student 2024
Join with us

Publications

Recent publications are as follows:

Bhattacharyya, K. Electrochemistry with Quantum Chemistry. EPJ Web of Conferences, 2022, 268, 00007

Bhattacharyya, K.; Auer, A. A. Oxygen Evolution Reaction Electrocatalysis on Cobalt(Oxy)hydroxide: Role of Fe Impurities. (Journal of Physical Chemistry C, 2022, 126, 18623-18635)

Yang, X.; Reijerse, E.; Bhattacharyya, K.; Auer, A. A.; Cornella, J. Radical Activation of N-H and O-H Bonds at Bismuth (II). ( Journal of American Chemical Society, 2022, 144, 16535-16544) ( Equal 2nd author contribution)

Ghosh, S.; Bhattacharyya, K., Origin of the Failure of Density Functional Theories in Predicting Inverted Singlet-Triplet Gaps. ( Journal of Physical Chemistry A, 2022, 126, 1378-1385) ( Equal contribution)

Schiavo, E., Bhattacharyya, K., Mehring, M., Auer., A. Are interactions between main group elements and π-systems really “π-interactions”? (Chemistry -A European Journal, 2021, 27, 14520-14526)

Bhattacharyya, K. Can TDDFT Render the Electronic Excited States Ordering of Azine Derivative? A Closer Investigation with DLPNO-STEOM-CCSD. Chemical Physics Letter (Chemical Physics Letter, 2021, 779, 138827)

Sreejyothi, P., Bhattacharyya, K., Datta, A., Mandal, S. An NHC-stabilized Phosphinidene for catalytic formylation: A DFT guided approach. Chemistry- A European Journal, 202, 27, 11656-11662).

Bhattacharyya, K., Poidevin, C., Auer, A. Structure and Reactivity of IrOx Nanoparticles for the Oxygen Evolution Reaction in Electrocatalysis: An Electronic Structure Theory Study. Journal of Physical Chemistry C. 2021, 125, 4379-4390

Pal, A. K., Bhattacharyya, K., Datta, A. Polymorphism Dependent 9-Phosphoanthracene Derivative Exhibiting Thermally Activated Delayed Fluorescence: A Computational Investigation. Journal of Physical Chemistry A. 2020, 124, 11025-11037.

Fritzsche, A., Scholz, S., Krasowska, M., Bhattacharyya, K., Toma, A., Silvestru, C., Korb, M., Auer, A., Mehring, M. Evaluation of bismuth-based dispersion energy donors–synthesis, structure and theoretical study of 2-biphenylbismuth (iii) derivatives. Physical Chemistry Chemical Physic. 2020, 18, 10189-10211.

Pal, A. K., Bhattacharyya, K., Datta, A. Remote Functionalization through Symmetric or Asymmetric Substitutions Control the Pathway of Intermolecular Singlet Fission. Journal of Chemical Theory and Computation. 2019, 15, 5014-5023.

Bhattacharyya, K., Datta, A. Computationally Driven Design Principles for Singlet Fission in Organic Chromophores. Journal of Physical Chemistry C, 2019,123, 19257-19268.

Bhattacharyya, K., Datta, A. Intra-molecular Singlet Fission in Quinoidal Dihydrothiophene. Journal of Physical Chemistry C, 2019, 21, 12346-12352.

Bhattacharyya, K., Datta. A. Visible light Driven Efficient Metal Free Single Atom Catalyst Supported Nanoporous Carbon Nitride for Nitrogen Fixation. Physical Chemistry Chemical Physics, 2019, 9, 651–659.