Reactions of Photoionization-Induced CO–H₂O Cluster: Direct Ab Initio Molecular Dynamics Study

Abstract

The hydrocarboxyl radical (HOCO) is an important species in combustion and astrochemistry because it is easily converted to CO 2 after hydrogen reduction. In this study, the formation mechanism of the HOCO radical in a CO–H 2 O system was investigated by direct ab initio molecular dynamics calculations. Two reactions were examined for HOCO formation. First, the reaction dynamics of the CO–H 2 O cluster cation, following the ionization of the neutral parent cluster CO(H 2 O) n ( n = 1–4), were investigated. Second, the bimolecular collision reaction between CO and (H 2 O) n + was studied. In the ionization of the CO(H 2 O) n clusters ( n = 3 and 4), proton transfer, expressed as CO(H 2 O) n + → CO–(OH)H 3 O + (H 2 O) n –2 , occurred within the (H 2 O) n + cluster cation, and the HOCO radical was yielded as a product upon addition of CO and OH. This reaction proceeds under zero-point energy. Also, this radical was effectively formed from the collision reaction of CO with water cluster cation (H 2 O) n + , expressed as CO + OH(H 3 O + )(H 2 O) n –2 → HOCO–H 3 O + + (H 2 O) n –2 . If the intermolecular vibrational stretching mode is excited in the CO(H 2 O) n cluster (vibrational stretching between CO and the water cluster), the HOCO radical was detected after ionization when n = 2. The reaction mechanism was discussed based on the theoretical results.

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

“…This specific property makes the GNF-Mg-H2 system suitable for use as a H2 storage device with adsorption-desorption reversible properties. In the following sections, the direct AIMD calculations [46][47][48] for the electron and hole capture processes of the GNF-Mg-H2 system are described [45].…”

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

“…The deviation in the total energy was less than 0.01 kcal/mol. The effects of ZPE on the reaction mechanism were investigated using the classical vibrational sampling method (microcanonical ensemble). − Direct AIMD calculations were carried out using our code. − …”

“…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).…”

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

“…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. − …”

“…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.…”