Research Interests

(A) Quantum dynamics without potential energy surfaces

This work aims to develop a method that describes the highly correlated coupled nuclear-electron dynamics, specially when the calculation involving all electronic eigenstates (potential energy surfaces) becomes unfeasible or impractical. For this purpose, we have developed an electron-nuclei dynamics scheme which makes use of the second quantization representation of the electrons. In this scheme, the electronic wavefunction is represented in a basis of quasi-diabatized molecular orbitals, and all non-adiabatic effects related to the coupling between nuclei and electrons are taken into account during the propagation. To represent the total (nuclear and electronic parts) wavefunction, we make use of the highly efficient and parallelized multiconfiguration time-dependent Hartree (MCTDH) method. The implemented method has been applied to study the non-adiabatic dynamics in various systems.

(B) Parity and time reversal (P, T-) violation in heavy polar molecules

The search for the violation of parity (P) and time reversal (T) symmetries in atom, molecule and ion is very important as it can explore new physics beyond the standard model. However, the experiment, alone cannot provide the evidence; the knowledge of various P, T -odd interaction constants like effective electric field (Eeff ) or scalar-pseudoscalar (S-PS) interaction constant (Ws), which cannot be measured by any experiment, is needed. Here, the main focus is the implementation of ab initio theory in the relativistic region that can produce accurate wave function in the nuclear region of heavy nucleus and the application of the implemented method to study various P, T-odd interaction constants of the relevant systems. We have implemented the extended coupled cluster (ECC) and the Z-vector method in the relativistic coupled cluster framework and identified RaF, PbF and HgH molecules as important players for the next generation electron electric dipole moment experiment due to their large Eeff and Ws.

(C) Electron attachment and detachment process in atoms and molecules

This work aims at the precise ab initio calculation of energies related to the electron attachment and detachment process of an atom or molecule. The accurate description of the energy spectrum of heavy atoms or molecules containg heavy atom(s) requires simultaneous incorporation of both the effects of relativity and electron correlation due to their intertwined nature. We have successfully implemented the equation-of-motion coupled cluster (EOMCC) method in the four-component relativisric framework to calculate the electron affinity, single and double ionization potential values of both close and open shell atomic and molecular systems.