ct4002174_si_001.pdf (1.81 MB)
Bending Vibration-Governed Solvation Dynamics of an Excess Electron in Liquid Acetonitrile Revealed by Ab Initio Molecular Dynamics Simulation
journal contribution
posted on 2013-11-12, 00:00 authored by Jinxiang Liu, Robert I. Cukier, Yuxiang BuWe
report an ab initio molecular dynamics simulation
study of the solvation and dynamics of an excess electron in liquid
acetonitrile (ACN). Four families of states are observed: a diffusely
solvated state and three ACN core-localized states with monomer core,
quasi-dimer (π*-Rydberg mode) core, and dual-core/dimer core
(a coupled dual-core). These core localized states cannot be simply
described as the corresponding anions because only a part of the excess
electron resides in the core molecule(s). The quasi-dimer core state
actually is a mixture that features cooperative excess electron capture
by the π* and Rydberg orbitals of two ACNs. Well-defined dimer
anion and solvated electron cavity were not observed in the 5–10
ps simulations, which may be attributed to slow dynamics of the formation
of the dimer anion and difficulty of the formation of a cavity in
such a fluxional medium. All of the above observed states have near-IR
absorptions and thus can be regarded as the solvated electron states
but with different structures, which can interpret the experimentally
observed IR band. These states undergo continuous conversions via
a combination of long-lasting breathing oscillation and core switching,
characterized by highly cooperative oscillations of the electron cloud
volume and vertical detachment energy. The quasi-dimer core and diffusely
solvated states dominate the time evolution, with the monomer core
and dual-core/dimer core states occurring occasionally during the
breathing and core switching processes, respectively. All these oscillations
and core switchings are governed by a combination of the electron-impacted
bending vibration of the core ACN molecule(s) and thermal fluctuations.