Our group focuses mainly on molecular many body theory, theoretical spectroscopy, finite temperature non-perturbative many body theories. We were the first to develop and implement a class of many-body methods for electronic structure, known as the Multireference Coupled Cluster methods, which are now standard works in the field. A long-standing problem of guaranteeing proper scaling of energy for many electron wave-functions of arbitrary complexity has also been first resolved by us.

Our research interests comprise of:

• Molecular electronic structure and theoretical spectroscopy
  • Back in 1975, we came up with the idea of Valence Universal Cluster expansion theories for difference energies. We also developed a linear response theory based on coupled cluster formalism (CCLRT).
• Quantum many-body dynamics
  • We have developed a general time – dependent perturbative theory which remains valid for arbitrarily large time range and is free from secular divergences. Later, it was generalized to the many – body regime and formulated the first general time-dependent coupled cluster theory for wave functions of arbitrary complexity.
• Statistical field theory
  • We have developed a rigorous finite – temperature field theory to study Statistical Mechanics of Many-Body systems. Unlike the traditional Thermofield Dynamics formulations, which maps a finite temperature theory to a zero-temperature one, the method has the advantage of working directly with the physical variables in the finite temperature range and is thus both more natural and compact
• Cummulant based quantum chemistry
  • We have also formulated an electron correlation theory for strongly correlated systems by starting from a combination of reference functions using a generalization of the usual Ursell-Meyer cluster expansion. In order to achieve this, he developed a Wick-like reduction formula using the concept of generalized normal ordering for arbitrary reference functions. An important spin-off from the Generalized Wick’s Theoremhad been the methods of directly determining the various reduced density matrices via generalized Brillouin’s theorem and the contracted Schrödinger equations
• State-specific Multireference (Mk-MR) Methods
  • Recently, we have developed a suite of state-specific many-body formalisms which bypass the difficulty of the notorious intruder problem for computing potential energy surfaces. These methods do not share the shortcomings of the previously used Effective Hamiltonian formalisms applied to cases warranting a multireference description.
• Relativistic coupled cluster theory
  • We have, very recently, developed one of the most versatile many-body methods which can predict with quantitative accuracy the energetics, hyperfine interactions and transition probabilities of heavy atoms and ions where relativistic effects are important.

Humbolt Research Award for Prof. Debashis Mukherjee:

Professor Debashis Mukherjee, currently the Chairman of Raman Centre for Atomic Molecular and Optical Sciences at Indian Association for the Cultivation of Science (IACS) , Kolkata, India, has been awarded the prestigious HUMBOLDT RESEARCH AWARD for his pioneering research in many-body electronic structure theory. The award is given by Alexander von Humboldt Foundation, Germany, to the academicians and scientists whose fundamental research and discoveries had left a significant impact on their field. The main research interests of Professor Mukherjee are in the Molecular Electronic structure theory and Theoretical Spectroscopy. He has developed over the years a suite of Multi-Reference Coupled Cluster theory and Relativistic Coupled Cluster theory for studying the structure and the energetics of ground and excited/ionized states of molecules of arbitrary complexity and generality. His work on the Fock Space Coupled Cluster Theory and the State-specific Coupled Cluster Theory are regarded ground-breaking, and are named after him.

He had been the Professor and also the Head of the Department of Physical Chemistry. He served as the Director of IACS from 1999 to 2008.

He is a Fellow of numerous academics , including the International Academy of Quantum Molecular Sciences, the Asia Pacific Association for Theoretical and Computational Chemists (APATCC), the American Institute of Chemists, the Indian Academy of Sciences, the Indian National Science Academy, to mention a few. He is a founder member of APATCC. He has been awarded the prestigious Fukui medal of the APATCC for his pioneering contributions in Coupled Cluster theory. He has delivered numerous Plenary and Key-note addresses in all the leading International Symposia like the ACS Annual meetings and the International Congresses in Quantum Chemistry. He was invited to deliver the Coulson Memorial Lecture of the Center of Computational and Quantum Chemistry in the University of Georgia, Atlanta, and the Fukui Memorial Lecture of the APATCC.

Will be available soon.