Reaction mechanism of an intracluster S N 2 reaction induced by electron capture

2022

Self Cite

Carbon materials such as graphene, carbon nanotubes, fullerene, and graphene nanoflakes (GNFs) are used for hydrogen storage. The doping of alkali metals to these materials generally increases the accumulation density of molecular hydrogen (H2). However, the reason why the doping enhances the ability of the H2 storage of GNF is not clearly known, although there are some explanations. In addition, the information on the storage capacity of GNF is ambiguous. In the present review article, we introduce our recent theoretical studies on the interaction of GNF with H2 molecules carried out to elucidate the mechanism of hydrogen storage in alkali-doped GNFs. As alkali metals, lithium (Li), sodium (Na), and potassium (K) were examined, and the abilities of hydrogen storage were discussed. Next, the mechanism of Li-diffusion on GNF, which plays a crucial role in Li-battery, was presented. There are several unanswered questions. In particular, does lithium diffuse randomly on GNF? Or is there a specific diffusion path? We present our study, which elucidates the factors governing lithium diffusion on GNF. If the dominant factor is known, it is possible to arbitrarily control the diffusion path of lithium. This will lead to the development of highly functional battery materials. Finally, the molecular design of H adsorption–desorption reversible storage devices based on GNF will be introduced. Elucidating the mechanism of hydrogen storage, Li-diffusion on GNF, and molecular design of storage device is important in understanding the current molecular devices and provide a deeper insight into materials chemistry.

Section: Electron Capture Dynamics Of Gnf-mg-h2mentioning

confidence: 99%

Hydrogen Storages Based on Graphene Nano-Flakes: Density Functional Theory Approach

2022

Self Cite

“…The effects of ZPE on the reaction mechanism were investigated using the classical vibrational sampling method (microcanonical ensemble). − The effects of the functional on the reaction mechanism were investigated using the ωB97XD functional and compared with those obtained with the CAM-B3LYP functional. Direct AIMD calculations were carried out using our own code. − …”

Section: Computational Detailsmentioning

confidence: 99%

“…In the present study, the reactions of ionized hydrogen peroxide–water clusters, denoted as [H 2 O 2 –(H 2 O) n ] + , after vertical ionization of neutral cluster, are investigated using the direct ab initio molecular dynamics (MD) method − to elucidate the effects of micro-solvation on the reaction of H 2 O 2 . Clusters with one to five water molecules, H 2 O 2 –(H 2 O) n ( n = 1–5), are examined.…”

Section: Introductionmentioning

confidence: 99%

Intracluster Reaction Dynamics of Ionized Micro-Hydrated Hydrogen Peroxide (H₂O₂): A Direct Ab Initio Molecular Dynamics Study

Yamasaki

2022

ACS Omega

Self Cite

Hydrogen peroxide (H 2 O 2 ) is a unique molecule that is applied in various fields, including energy chemistry, astrophysics, and medicine. H 2 O 2 readily forms clusters with water molecules. In the present study, the reactions of ionized H 2 O 2 –water clusters, H 2 O 2 + (H 2 O) n , after vertical ionization of the parent neutral cluster were investigated using the direct ab initio molecular dynamics (AIMD) method to elucidate the reaction mechanism. Clusters with one to five water molecules, H 2 O 2 –(H 2 O) n ( n = 1–5), were examined, and the reaction of [H 2 O 2 + (H 2 O) n ] ver was tracked from the vertical ionization point to the product state, where [H 2 O 2 + (H 2 O) n ] ver is the vertical ionization state (hole is localized on H 2 O 2 ). After ionization, fast proton transfer (PT) from H 2 O 2 + to the water cluster (H 2 O) n was observed in all clusters. The HOO radical and H 3 O + (H 2 O) n −1 were formed as products. The PT reaction proceeds directly without an activation barrier. The PT times for n = 1–5 were calculated to be 36.0, 9.8, 8.3, 7.7, and 7.1 fs, respectively, at the MP2/6-311++G(d,p) level, indicating that PT in these clusters is a very fast process, and the PT time is not dependent on the cluster size ( n ), except in the case of n = 1, where the PT time was slightly longer because the bond distance and angle of the hydrogen bond in n = 1 were deformed from the standard structure. The reaction mechanism was discussed based on these results.

“…The reactions are as follows ( H 2 ) n + normalh normalv → false[ ( H 2 ) n + ] normalv normale normalr , .25em normali normalo normaln normali normalz normala normalt normali normalo normaln false[ ( H 2 ) n + ] normalv normale normalr → normalp normalr normalo normald normalu normalc normalt ( P D ) where [(H 2 ) n + ] ver is the vertical ionization state of the (H 2 ) n cluster. The direct ab initio molecular dynamics (AIMD) method − was applied in reaction (5).…”

Section: Introductionmentioning

confidence: 99%

“…The reactions are as follows where [(H 2 ) n + ] ver is the vertical ionization state of the (H 2 ) n cluster. The direct ab initio molecular dynamics (AIMD) method − was applied in reaction (5).…”

Section: Introductionmentioning

confidence: 99%

Formation Mechanism of Odd- and Even-Numbered Hydrogen Cluster Cations Using the Direct Ab Initio Molecular Dynamics Approach

2022

J. Phys. Chem. A

Self Cite

The photoreaction of hydrogen clusters caused by cosmic-ray irradiations plays a crucial role in interstellar molecular clouds because the reaction of molecules takes place in these surrounding clusters. Previous gas-phase experiments introduced the reaction products after the ionization of the neutral hydrogen cluster. In the experiments, the odd-numbered hydrogen cluster cation, H+(H2) m , was the main product, while the even-numbered cluster cation, (H2) n +, was the minor product. However, the formation yield of (H2) n + was significantly low. Despite many theoretical calculations and experiments, the formation mechanism of odd- and even-numbered cluster ions from ionized hydrogen clusters is still unclear. In this study, the direct ab initio molecular dynamics (AIMD) method was applied to the reaction of the hydrogen cluster cation (H2) n + to understand the abovementioned formation mechanism. The trajectories of (H2) n + following the vertical ionization of the neutral cluster were calculated. Direct AIMD calculations indicated that odd-numbered cluster cations, H3 +(H2) n−2 + H (dissociation), were formed directly as the main product after the ionization of (H2) n . An even-numbered cluster, (H2) n +, was temporally formed when an H-shaped complex composed of three H2 molecules existed within a neutral cluster. However, it was rapidly dissociated to an odd-numbered cluster. Static ab initio calculations suggested that the odd-numbered cluster complex, H3 +(H2) n−2-H, could be transferred to even-numbered ions via a transition state with a low energy barrier. The even-numbered cluster cation was formed stepwise from the odd-numbered cluster cation. The formation mechanism of odd- and even-numbered cluster cations is discussed based on these results.