Non-adiabatic Excited-State Molecular Dynamics: Theory and Applications for Modeling Photophysics in Extended Molecular Materials

Abstract

Optically active molecular materials, such as organic conjugated polymers and biological systems, are characterized by strong coupling between electronic and vibrational degrees of freedom. Typically, simulations must go beyond the Born− Oppenheimer approximation to account for non-adiabatic coupling between excited states. Indeed, non-adiabatic dynamics is commonly associated with exciton dynamics and photophysics involving charge and energy transfer, as well as exciton dissociation and charge recombination. Understanding the photoinduced dynamics in such materials is vital to providing an accurate description of exciton formation, evolution, and decay. This interdisciplinary field has matured significantly over the past decades. Formulation of new theoretical frameworks, development of more efficient and accurate computational algorithms, and evolution of high-performance computer hardware has extended these simulations to very large molecular systems with hundreds of atoms, including numerous studies of organic semiconductors and biomolecules. In this Review, we will describe recent theoretical advances including treatment of electronic decoherence in surface-hopping methods, the role of solvent effects, trivial unavoided crossings, analysis of data based on transition densities, and efficient computational implementations of these numerical methods. We also emphasize newly developed semiclassical approaches, based on the Gaussian approximation, which retain phase and width information to account for significant decoherence and interference effects while maintaining the high efficiency of surface-hopping approaches. The above developments have been employed to successfully describe photophysics in a variety of molecular materials.

Predicting in silico electron ionization mass spectra using quantum chemistry

“…Changing parameters in QCEIMS was not a viable method to improve simulation results. Likely, capturing the potential energy surface accurately or even conducting the excited-state molecular dynamics [35,36] can be the key to further improving EI-MS prediction. For the first time, QCEIMS simulation was tested on hundreds of small organic molecules with limited computational resources within 1 month.…”

Predicting in-silico electron ionization mass spectra using quantum chemistry

“…Changing parameters in QCEIMS was not a viable method to improve simulation results. Likely, capturing the potential energy surface accurately or even conducting the excited-state molecular dynamics [35,36] can be the key to further improving EI-MS prediction. For the rst time, QCEIMS simulation was tested on hundreds of small organic molecules with limited computational resources within one month.…”

Predicting in-silico electron ionization mass spectra using quantum chemistry

“…Changing parameters in QCEIMS was not a viable method to improve simulation results. Likely, capturing the potential energy surface accurately or even conducting the excited-state molecular dynamics [35,36] can be the key to further improving EI-MS prediction. For the first time, QCEIMS simulation was tested on hundreds of small molecules with limited computational resources within one month.…”