Data from: Potentials of mean force fail to describe chemical bond-breaking in solution

Many liquid phase studies assume that the potential energy surfaces of
reacting molecules are the same as in the gas phase, neglecting complex
solvent dynamics that can completely alter the nature of chemical
reactivity. Even studies that include solvent effects typically only
consider them in an average, equilibrium way as part of a potential of
mean force (PMF). In this work, we use mixed quantum/classical simulations
to compare how equilibrium and non-equilibrium solvent motions affect the
photodissociation of a simple diatomic molecule, NaK+, in liquid
tetrahydrofuran. A PMF analysis shows that as the excited-state molecule
dissociates with the solvent at equilibrium, the bonding electron remains
associated with K+ at short bond distances but eventually localizes on Na+
at the end of dissociation.  When we examine nonequilibrium
dynamical photodissociation trajectories, however, we find that they fall
into three distinct categories: about a quarter of them have the bonding
electron mainly associated with Na+, another quarter stay mainly
associated with K+, and about half have the bonding electron shared
roughly equally between the two ions. The results show that equilibrium
PMFs cannot accurately describe the dynamics of bond-breaking chemical
reactions in solution, because there is insufficient time for the solvent
to reach equilibrium on the time scale over which bond dissociation
occurs.