On the ion‐pair dissociation mechanisms in the small NaCl·(H₂O)₆ cluster: A perspective from reaction path search calculations

Abstract

We performed reaction path search calculations for the NaCl·(H O) cluster using the global reaction route mapping (GRRM) code to understand the atomic-level mechanisms of the NaCl → Na + Cl ionic dissociation induced by water solvents. Low-lying minima, transition states connecting two local minima and corresponding intrinsic reaction coordinates on the potential energy surface are explored. We found that the NaCl distances at the transitions states for the dissociation pathways were distributed in a relatively wide range of 2.7-3.7 Å and that the NaCl distance at the transition state did not correlate with the commonly used solvation coordinates. This suggests that the definition of the transition states with specific structures as well as good reaction coordinate is very difficult for the ionic dissociation process even in a small water cluster. © 2018 Wiley Periodicals, Inc.

Pair-Reaction Dynamics in Water: Competition of Memory, Potential Shape, and Inertial Effects

“…Snapshots from the MD simulation illustrate the different states in Figure A. In fact, the TS in this one-dimensional projection corresponds to an ensemble of disparate states that do not single out well the actual TS in an enlarged multidimensional description. , This however is not a problem for our kinetic description using the GLE, since non-Markovian effects, caused by dimensional reduction, are fully accounted for. Note that the confinement potential U con ( x ) changes the barrier height from the CP to the TS state slightly, as seen by comparing U ( x ) (solid line) and U ( x ) – U con ( x ) (broken line) in Figure A.…”

Structural Versatility and Energy Difference of Salt–Water Complex NaCl(H2O) Encoded in Cryogenic Photoelectron Spectroscopy

“…Understanding the microscopic behavior of salts in solution is one of the most fundamental questions in physical chemistry. − The salt–water complex NaCl­(H 2 O) is a basic model system for understanding the solvation of salts in water at a molecular level. Recently, many theoretic and experimental studies have been performed on NaCl­(H 2 O) n clusters, such as ab initio calculations, − argon-matrix infrared spectroscopy, helium-nanodroplet infrared spectroscopy, Fourier transform microwave spectroscopy, , and anion photoelectron spectroscopy . These studies have shown that small clusters NaCl­(H 2 O) n usually have several isomers close in energy due to the weak noncovalent interactions.…”

Physical insight into the entropy‐driven ion association

“…A series of ion pairing systems are selected from the monoatomic to polyatomic ions. As the most widely studied electrolyte through experimental techniques and theoretical simulations, 39,42,46–49 Na + –Cl − is chosen as the representative electrolyte not only to provide benchmark to validate the proposed computational strategy here, but also to offer direct comparison to the association of polyatomic ions, Ca 2+ –CO 3 2− and Ca 2+ –HPO 4 2− . The selected two polyatomic ions, broadly existing in nature, play a pivotal role in biological environment and life activities, and have been studied with extensive experimental and computational data available for comparison 50–53 .…”

“…A series of ion pairing systems are selected from the monoatomic to polyatomic ions. As the most widely studied electrolyte through experimental techniques and theoretical simulations, 39,42,[46][47][48][49] Na + -Cl À is chosen as the representative electrolyte not only to provide benchmark to validate the proposed computational strategy here, but also to offer direct comparison to the association of polyatomic ions, Ca 2+ -CO 3 2À and Ca 2+ -HPO 4…”