The electron force field (eFF) models electrons as Gaussian wave packets whose centers and widths evolve according to classical equations of motion. This unconventional approach allows the simulation of nonadiabatic electron dynamics at a cost comparable to standard molecular dynamics. Herein, we present the first systematic benchmark of eFF for prototypical problems in water radiation chemistry. We show that the original eFF1 model and the eFF-ECP extension do not reproduce a stable ground-state geometry for a water monomer, whereas the eFF2 model recovers the correct monomer minimum, yet still overestimates hydrogen bond energies in water clusters. For dynamical observables, eFF2 captures key features of water electronic stopping for various projectiles (H+, He2+, Li3+, and electrons), including velocity-dependent projectile charge-state populations. It also reproduces the femtosecond dynamics of valence-ionized water monomers and dimers in good agreement with previous multireference ab initio results. However, cross sections describing proton-water collisions are largely underestimated, both for charge-transfer and fragmentation decay channels. Overall, these results establish eFF as a computationally efficient exploratory framework for ultrafast radiation-induced processes. Its primary value lies in revealing qualitative trends and identifying new mechanistic pathways, rather than providing quantitative reaction probabilities.
Tomáš Ovad, P. Slavíček· Physical Chemistry, Chemical...· 0 citations
Charge-transfer-to-solvent (CTTS) excitations provide a chemically central route to generating hydrated electrons and initiating redox chemistry in solution, yet the earliest stage of CTTS---the formation of the excited state itself---is usually treated as instantaneous. Here we present a time-domain perspective of how CTTS character builds up during core-level photoexcitation of an aqueous metal ion. Using time-dependent configuration interaction, we simulate the coherent evolution of a dense manifold of core-excited states and track the ultrafast flow of electronic charge from the initially localized site into solvent-supported final states. We find that the dynamics evolves from a few-state, oscillatory behavior to effectively irreversible delocalization, as the charge disperses among many coupled configurations, providing a microscopic mechanism for the early-time emergence of CTTS character. Our results offer a transparent real-time interpretation of what core-level spectroscopies and core-hole-clock-type measurements can probe in solutions, outlining experimental signatures for probing the build-up of CTTS states on the core-hole-lifetime timescale. Looking ahead, attosecond and sub-femtosecond X-ray pump--probe approaches at X-ray free-electron lasers provide a realistic route to directly time-resolve the core-excited CTTS wave packets in solution.
Jiří Suchan, B. S. Fales, Benjamin G. Levine et al.· 0 citations
Solute-solvent interactions are fundamental to understanding the stability, reactivity, and biological function of molecules. Spectroscopic techniques allow gaining molecular-level insights into these interactions. Here we explore the hydration of uracil, a model system for the behavior of biomolecules in an aqueous environment. We combine experimental liquid-jet photoemission spectroscopy with different theoretical approaches to investigate the element-specific core-level binding energies of solvated uracil and what they reveal about solvation. The maximum overlap method (MOM) approach combined with density functional theory (DFT) is applied to calculate the binding energies of DFT-optimized micro-hydrated clusters with an additional non-equilibrium dielectric continuum modeling long-range solvent interactions. The latter proves to be crucial but sufficient to describe the case of neutral uracil. On the other hand, for deprotonated uracil, structures extracted from QM/MM molecular dynamics provide more accurate binding energies. Both cases highlight the need to go beyond micro-hydration and to describe the full solvation, although in different ways. The conjugation of experiment and theory also allowed us to clearly identify the site of deprotonation of uracil. The present findings represent quantitative experiment-theory benchmarks on representative solvated molecules.
Marine Fournier, Martin Procházka, Rémi Dupuy et al.· Physical Chemistry, Chemical...· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
