An efficient and flexible approach for computing rovibrational polaritons from first principles

Abstract

A theoretical framework is presented for the computation of the rovibrational polaritonic states of a molecule in a lossless infrared (IR) microcavity. In the proposed approach, the quantum treatment of the rotational and vibrational motions of the molecule can be formulated using arbitrary approximations. The cavity-induced changes in electronic structure are treated perturbatively, which allows using the existing polished tools of standard quantum chemistry for determining electronic molecular properties. As a case study, the rovibrational polaritons and related thermodynamic properties of H2O in an IR microcavity are computed for varying cavity parameters, applying various approximations to describe the molecular degrees of freedom. The self-dipole interaction is significant for nearly all light–matter coupling strengths investigated, and the molecular polarizability proved important for the correct qualitative behavior of the energy level shifts induced by the cavity. On the other hand, the magnitude of polarization remains small, justifying the perturbative approach for the cavity-induced changes in electronic structure. Comparing results obtained using a high-accuracy variational molecular model with those obtained utilizing the rigid rotor and harmonic oscillator approximations revealed that as long as the rovibrational model is appropriate for describing the field-free molecule, the computed rovibropolaritonic properties can be expected to be accurate as well. Strong light–matter coupling between the radiation mode of an IR cavity and the rovibrational states of H2O leads to minor changes in the thermodynamic properties of the system, and these changes seem to be dominated by non-resonant interactions between the quantum light and matter.

Machine Learning for Polaritonic Chemistry: Accessing Chemical Kinetics

“…If we intend to widely scan those parameters or would like to include more than a single mode, it becomes, however, practically unfeasible. A (self-consistent) perturbative correction ,, to the electronic quantities might suffice to suppress some of the problematic features. Such a correction could be constructed via static electronic polarizabilities, which can be predicted with an additional neural network, to correct the electronic energies and dipole moments according to the adiabatic cavity field.…”

A Quantum Chemistry Approach to Linear Vibro-Polaritonic Infrared Spectra with Perturbative Electron–Photon Correlation

“…19 We note, CBO-PT is conceptually similar to other perturbative approaches, 20,21 which however constitute a further approximation 19,20 or do not directly connect to the CBO formulation. 21 In this work, we introduce an approximation to the nonperturbative CBO linear response framework of Bonini and Flick 15 by combining CBO-PT with linear response theory. This approach allows us to systematically correct vibropolaritonic IR spectra for electron−photon correlation effects while fully relying on molecular properties that can be accessed by ab initio quantum chemistry methods.…”

“…19 CBO-PT solves the extended CBO electronic structure problem perturbatively and allows for systematic electron−photon correlation corrections of the crude CBO approach. 19 We note, CBO-PT is conceptually similar to other perturbative approaches, 20,21 which however constitute a further approximation 19,20 or do not directly connect to the CBO formulation. 21 In this work, we introduce an approximation to the nonperturbative CBO linear response framework of Bonini and Flick 15 by combining CBO-PT with linear response theory.…”

“…CBO-PT solves the extended CBO electronic structure problem perturbatively and allows for systematic electron–photon correlation corrections of the crude CBO approach . We note, CBO-PT is conceptually similar to other perturbative approaches, , which however constitute a further approximation , or do not directly connect to the CBO formulation …”

“…This approach allows us to systematically correct vibro-polaritonic IR spectra for electron–photon correlation effects while fully relying on molecular properties that can be accessed by ab initio quantum chemistry methods. We derive explicit expressions for electron–photon correlation-corrected vibro-polaritonic Hessian matrix elements and IR intensities, which are both shown to be determined by the molecule’s static polarizability, whose possible relevance has been noted only recently. − We illustratively apply the CBO-PT linear response approach to vibro-polaritonic model systems of CO 2 and Fe­(CO) 5 (cf. Figure ) in line with ref and discuss electron–photon correlation effects in connection to experimentally relevant transmission spectra. , …”