Convergence of Theory and Experiment Reveals the Surprising Role of Quantum Effects in Chloride Solvation

Path-integral ab initio molecular dynamics (PI-AIMD) calculations have been employed to probe
the nature of chloride ion solvation in aqueous solution. Nuclear quantum e_ects (NQEs) are shown to weaken hydrogen bonding between solvation shell water and the chloride anion. As a consequence, the disruptive effect of the anion on the underlying solvent water structure is significantly reduced compared to what is found in the absence of NQEs. The PI-AIMD computed chloride hydration structure agrees well with information extracted from neutron scattering data. In particular, the observed satellite peak in the hydrogen-chloride-hydrogen triple angular distribution serves as a clear signature of NQEs. The present results imply that NQEs are likely to play a crucial role in determining the structure of saline solutions.