Title:	Development and application of new nonadiabatic dynamics methods to investigate photoinduced molecular processes
DNr:	SNIC 2022/22-1081
Project Type:	SNIC Small Compute
Principal Investigator:	Rafael Carvalho Couto <rcc@kth.se>
Affiliation:	Kungliga Tekniska högskolan
Duration:	2022-11-09 – 2023-12-01
Classification:	10407
Keywords:

Abstract

Photoinduced processes underpin an ever-expanding range of technological applications, such as photovoltaics, sensors, imaging and photocatalysts. Photons offer multiple advantages as low-loss energy carriers but also in the context of matter: providing a window into its quantum nature, triggering and driving transformations as well as externally controlling them. This project is concerned with understanding the inner workings of photoinduced processes in molecular systems by developing and using a combination of nonadiabatic dynamics simulations and calculations of their spectroscopic signatures (both electron, optical and X-ray-based). On the applicational side, we will for instance investigate internal conversion decay pathways in a prototype excited-state hydrogen transfer (ESIHT) system and their competition with intersystem crossing.[1] ESIHT is a one of the fastest chemical reactions and plays a key role in a range of light-induced biological processes and technological applications. In collaboration with leading experimentalists in the field (key collaborators: Thomas A. Wolf and Ruaridh J. G. Forbes, Stanford University) we successfully procured and conducted two LCLS experiments on acetylacetone photoexcited to its pi-pi* state that have resulted in rich sets of time-resolved X-ray absorption and X-ray scattering data. To facilitate interpretation of these experiments, we will perform ab initio multiple spawning (AIMS) simulations in combination with calculations of the spectroscopic observables. Beyond gas-phase systems, we are investigating photoinduced dynamics in condensed phases and photoactive proteins using hybrid QM/MM approaches.[2] The aim of this research is to decipher the implications of the surrounding environment on the excited-state deactivation. We are particularly interested in disentangling the effects of mutations in photo-reversibly switching fluorescent proteins with direct relevance for the development of new biomarkers and optogenetic applications. The nonadiabatic dynamics simulations will be performed primarily using the FMS90 dynamics program coupled with the GPU-accelerated electronic structure package TeraChem and to a lesser extent using CPU-based quantum chemistry codes (e.g., BAGEL, OpenMolcas, VeloxChem and DIRAC). On the development side, we will pursue two directions. First, we will develop a new flexible nonadiabatic dynamics package that scales with the problem size and allows for faster implementation and testing of new features. This development will serve as platform to enable the second direction where we will investigate possible routes to improve (i) the initial conditions sampling for excited-state simulations and (ii) the description of energy redistribution during the photoinduced nonequilibrium dynamics. [1] List et al. Chem. Sci., 2020,11, 4180-4193 [2] List et al. Chem. Sci., 2022, 13, 373; Jones et al. Chem. Sci., 2021, 12, 11347; Jones et al., J. Am. Chem. Soc., 2022, DOI: 10.1021/jacs.2c02946; List et al. in preparation.