Proper treatment of electron-correlation effects is very often necessary for quantitative (sometimes also for qualitative) description of electronic structure of atoms and molecules. Molecules with closed-shell electronic structure can be well-described by quantum chemical methods available in many program packages. Description of open-shell electronic structures commonly occurring in many chemical phenomena involving bond-dissociation, excited states and transition metal complexes generally requires more sophisticated methods known as multi-reference (MR) methods. My research focuses on development and applications of quantum chemical methods applicable for such situations.
My current interest is on MR methods making use of the concept of internally contracted (IC) excitations. The IC excitations are known to be compact form of excitation manifold required to correlate a zeroth-order approximation to the full wave-function. Recently, I have been involved in the development of a multi-reference configuration interaction (MRCI) method based on IC excitations. We have demonstrated the efficiency and applicability of the new method to medium size molecules such as metallocenes and dioxygen bound mono and di-copper complexes with moderately large ligands. Currently, I am working to extend this method for the treatment of excited state potential energy surfaces and molecular properties. In near future, I plan to explore some of the possibilities for IC multi-reference coupled-cluster methods which have the potential to be more accurate.
I am also interested in applying the standard as well as the newly developed methods to some interesting chemical problems involving reaction pathways and dynamics on excited potential surfaces.
- K.R. Shamasundar, Gerald Knizia, and Hans-Joachim Werner ., "A new multi-reference configuration interaction method" (under preparation).
- K. R. Shamasundar , "Cumulant decomposition of reduced density matrices, multireference normal ordering, and Wicks theorem: A spin-free approach", J. Chem. Phys. 131, 174109 (2009).
- L. Kong, K. R. Shamasundar, O. Demel, and M. Nooijen ., "State specific equation of motion coupled cluster method in general active space", J. Chem. Phys. 130, 114101 (2009).
- K. R. Shamasundar, S. Asokan, S. Pal ., "A constrained variational approach for energy derivatives in Fock-space multireference coupled-cluster theory" , J. Chem. Phys. 120, 6381 (2004).
- K. R. Shamasundar, S. Pal ., "Development of an efficient linear response approach to the Hilbert space multi-reference coupled-cluster theory" , J. Chem. Phys. 114, 1981 (2001)