Relativistic electronic structure theory

Development and Implementation of Coupled-Cluster-Theory-Based Methods for Static Properties 

Coupled cluster (CC) theory being a wavefunction-based method has earned the reputation of being the “gold standard” in computational chemistry. The inclusion of relativistic effects into such a wavefunction-based method is very important for accurately describing the energy levels and predicting various spectroscopic and chemical properties of heavy atomic and molecular systems. Properties such as the electron’s electric dipole moment (eEDM) and parity nonconservation (PNC) can’t even be described without the relativistic theory. Relativistic electronic structure theory is essential for the accurate calculation of various molecular parameters (also known as the P, T-odd molecular parameters) that are required for the analysis of the results of high-precision spectroscopic experiments. The four-component relativistic coupled cluster method, which can efficiently incorporate both the relativistic effects of electrons and the electron-correlation effects, has become the cutting-edge tool for quantum chemists and molecular physicists for the accurate prediction of such properties. However, the successful implementation of relativistic CC-based methods to compute the energy levels and the spectroscopic properties is not a trivial task due to the intertwined nature of the relativistic and the electron correlation effects as well as the very high computational cost and higher order scaling. We are interested in developing and implementing efficient relativistic many-body methods within the single-reference coupled cluster framework for high-precision calculations of energy and static properties of heavy-elemental molecular systems.

Molecular Symmetry Violating Effects

The presence of T-violating interactions or CP violations (where T, C, and P mean time-reversal, charge conjugation, and parity symmetry, respectively) can help to unravel the physics behind matter-antimatter asymmetry of the known universe. The existence of the permanent electric dipole moment (EDM) and magnetic quadrupole moment (MQM) of a particle is a direct signature of CP violation, and the experimental search for CP-violating physics is now a cutting-edge area of research. We investigate the electronic structure of interesting molecules in search of CP-violating physics using relativistic ab initio methods. Our work can propose suitable molecular candidates for CP-odd high-precision experiments and also provide the precise value of the electronic structure parameters required to interpret the results of such experiments.

Detection of molecular parity violation can shed some light on the mystery of chiral purity of biochemical monomers. The P-odd effects in chiral compounds should result in a tiny difference in energy between enantiomers, which, in principle, can be measured from high-precision spectroscopic experiments. We are interested in high-precision calculations of various P-odd effects in heavy elemental molecules to guide and support the said molecular experiments.

Chemistry and Spectroscopy of Heavy-Elemental Compounds

Relativistic effects are prominent in heavy & super-heavy elements and their compounds. Therefore, efficient treatment of the relativistic effects along with the electron-correlation effects is crucial for the accurate prediction of the chemistry and spectroscopy of those systems. Our work focuses on accurately predicting the chemical and spectroscopic properties of such (super-)heavy-elemental systems by applying the relativistic many-body theories.