First-Principles Molecular and Reaction Dynamics Simulations: Application to the Structure, Thermodynamics and Photochemistry of Ionic Aqueous Clusters

摘要

Realistic computer simulations of the structure and thermodynamics of complex chemical systems governed by subtle intermolecular interactions, as well as the real time-evolution of such systems in their electronically excited states, resulting for example from photoexcitation, represent many challenges for modern computational chemistry. In this contribution, we discuss the application of first-principles molecular dynamics simulations to the ground-state structure and thermodynamics and the excited-state dynamics of iodide-water clusters. One of the fascinating features of these clusters lies in the possibility of photochemical transfer of an electron from the ion to the solvent, giving rise to so-called charge-transfer-to-solvent excited states, which arises from surface solvation structures in small to medium-sized clusters and eventually lead to precursor states of the solvated electron. We will thus discuss a rigorous investigation of surface vs. interior solvation thermodynamics for these species, we will show how reliable calculations of energetics, vertical excitation energies and ionization potentials can be combined with experiment to probe cluster solvation structures, and we will highlight the importance of solvation dynamics in the relaxation of photoexcited ionic clusters, in connection with recent femtosecond photoelectron spectroscopy experimental results.