Jankunas Dissertation Award (Finalists): Ab Initio Simulations of Molecular Quantum Dynamics and Exciton-Polaritons
ORAL · Invited
Abstract
Coupling molecules to quantized radiation fields, forming hybrid light-matter states called polaritons, has shown great promise to modify chemical, photo-chemical, and photo-physical properties. There are many challenges in simulating such hybrid systems. One such challenge is simulating the quantum dynamics of the hybrid system, which is often a necessary tool in understanding the complicated interplay among the electronic, nuclear, and photonic degrees of freedom. Another challenge has been to accurately simulate the polaritonic structure (i.e., analogous to electronic structure) from first principles without reinventing standard many-body approaches used in electronic structure theory.
In this thesis, we first explore multiple ab initio molecular systems using state-of-the-art mean-field quantum dynamics approaches, including various flavor of symmetric quasi-classical (SQC), fully linearized spin-mapping (spin-LSC), and partially linearized spin-mapping (spin-PLDM). We use the quasi-diabatic scheme, which is a locally diabatic representation used to propagate the quantum (e.g., electronic, photonic) and classical (e.g., nuclear) degrees of freedom by assuming that the adiabatic quantum states are diabatic states between adjacent nuclear geometries. This approach seamlessly connects the diabatic quantum dynamics methods with adiabatic electronic structure theory. We next establish an ab initio approach, parameterized quantum electrodynamics (pQED), for simulating strongly coupled systems using output from standard electronic structure calculations as input into the non-relativistic Pauli-Fierz Hamiltonian. We compare our approach to various self-consistent QED (scQED) approaches for both cavity-modified ground and excited state Born-Oppenheimer potential energy surfaces as well as polaritonic real-space transition density. We further explored polaritonic natural transition orbitals (pNTOs) of a charge transfer system. We have since applied this approach to a textbook organic chemical reaction generating an impossible product inside the cavity as well as to exploring realistic linear spectroscopy of collectively coupled molecules inside the cavity including molecular energetic and orientational disorder.
In this thesis, we first explore multiple ab initio molecular systems using state-of-the-art mean-field quantum dynamics approaches, including various flavor of symmetric quasi-classical (SQC), fully linearized spin-mapping (spin-LSC), and partially linearized spin-mapping (spin-PLDM). We use the quasi-diabatic scheme, which is a locally diabatic representation used to propagate the quantum (e.g., electronic, photonic) and classical (e.g., nuclear) degrees of freedom by assuming that the adiabatic quantum states are diabatic states between adjacent nuclear geometries. This approach seamlessly connects the diabatic quantum dynamics methods with adiabatic electronic structure theory. We next establish an ab initio approach, parameterized quantum electrodynamics (pQED), for simulating strongly coupled systems using output from standard electronic structure calculations as input into the non-relativistic Pauli-Fierz Hamiltonian. We compare our approach to various self-consistent QED (scQED) approaches for both cavity-modified ground and excited state Born-Oppenheimer potential energy surfaces as well as polaritonic real-space transition density. We further explored polaritonic natural transition orbitals (pNTOs) of a charge transfer system. We have since applied this approach to a textbook organic chemical reaction generating an impossible product inside the cavity as well as to exploring realistic linear spectroscopy of collectively coupled molecules inside the cavity including molecular energetic and orientational disorder.
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Publication: J. Chem. Phys. 155, 084106 (2021)
J. Chem. Phys. 157, 194109 (2022)
J. Phys. Chem. Lett. 2023, 14, 25, 5901–5913
Phys. Chem. Chem. Phys., 2023, 25, 31554-31577
Chem. Rev. 2023, 123, 16, 9786–9879
Phys. Rev. A 109, 032804 (2024)
Phys. Rev. B 109, 104305 (2024)
J. Am. Chem. Soc. 2024, 146, 23, 16184–16193
J. Chem. Phys. 162, 084105 (2025)
J. Phys. Chem. A 2025, 129, 25, 5458–5468
Phys. Rev. A 112, 013713 (2025)
Presenters
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Braden M Weight
- Los Alamos National Laboratory
- Los Alamos National Laboratory (LANL)