Our research is focused on theoretical modeling of open-shell molecules. Since chemical transformations involve bond-breaking, radicals and diradicals are often encountered as reaction intermediates or transition states. Therefore, they play a central role in mechanistic understanding of processes important in the environment, synthetic chemistry, material science, biochemistry, etc. Since these open-shell species are often very reactive and short-lived, their experimental observations are difficult. That is why electronic structure theory is a valuable tool for studying their properties.

Equation-of-motion (EOM) is a versatile electronic structure approach that allows one to describe many multi-configurational wave functions within a single-reference formalism. For example, EOM for excitation energies (EOM-EE) method accurately describes electronically excited states, while ionized/electron attached EOM models (EOM-IP/EA) can tackle doublet radicals, including notorious cases of symmetry breaking. We have extended EOM approach to diradicals, triradicals, and bond-breaking. In our approach, which is called the Spin-Flip (SF method) problematic low-spin states are treated as spin-flipping excitations from the high-spin reference state.

We are fascinated by electronic structure and bonding in triradicals, species with three unpaired electrons.

To model angular distributions of photoelectrons, we implemented the calculation of Dyson orbitals using EOM-EE/IP/EA-CCSD.

Electron transfer reactions are common in biological and synthetic polymers. The rates of these processes can be related to the coupling between the diabatic electronic states that correspond to reactant and product states. Calculations on these systems are difficult due to the propensity of Hartree-Fock solutions to overlocalize charge and break symmetry.

As a part of spectroscopy modeling unit of programs, we develop a code for wavepacket propagation.

We characterized the ground and electronically excited states of cyclic N₃⁺ at the equilibrium D_3h geometry and along Jahn-Teller distortions.

Radicals are ubiquitous in chemistry, and it is not surprising that they play an important role in atmosphere (think ozone) and in catalysis (after all, it is all about breaking and making bonds).

In collaboration with several experimental and theoretical groups, complex photodissociation dynamics of the NO dimer were uncovered. (NO)₂ is unstable at room temperature, but exists in cold atmospheres and on cold surfaces, where it behaves differently than the NO radical. It strongly absorbs UV radiation and falls apart.

Carbon trioxide plays an important role in atmospheric chemistry and has been detected in interstellar ices. However, its ground state symmetry has eluded both experimental and computational chemists for decades.