Electron detachment dynamics of O₂⁻(H₂O): direct ab initio molecular dynamics (AIMD) approach

Abstract

Electron detachment dynamics of the hydrated superoxide anion O 2 À (H 2 O) have been investigated by means of direct ab initio molecular dynamics (AIMD) methods. Two potential energy surfaces were examined as electronic states of oxygen molecule after the electron detachment of the hydrated superoxide anion: O 2 ( 3 S)(H 2 O) and O 2 ( 1 D)(H 2 O). In both electronic states, the dissociation products, O 2 + H 2 O, were obtained. However, the internal states of O 2 were essentially different from each other. On the triplet state surface, the O-O stretching mode of O 2 ( 3 S) was excited, whereas that of O 2 ( 1 D) was silent. The reaction mechanism was discussed on the basis of theoretical results.

Ab Initio Molecular Dynamics Investigation of the Electronic and Structural Stability of Anionic O2–(H2O)n, n = 1–16 Clusters

“…Additionally, the dissociation energies of the (H 2 O) n clusters with n = 2–5, Δ E = E­[(H 2 O) n ] – n *E­[(H 2 O)], agree very well with the high-level MP2/aug-cc-pV5Z calculations of Xantheas et al Next, we calculated the anionic O 2 – and neutral O 2 bond distances to be 1.391 and 1.241 Å which compare well with the experimental 1.348 ± 0.008 and 1.2075 Å values, respectively. We then calculated the water dissociation energy to O 2 – (H 2 O) n with n = 0–2, Δ E = E [O 2 – (H 2 O) n ] – E [O 2 – (H 2 O) n ‑1 ] – E [(H 2 O)], and compared our results with available experimental , and theoretical MP2/6-311++G­(d,p) reports, finding a good agreement with a difference of less than 0.2 eV. Finally, we calculated vertical and adiabatic electron detachment energies and compared our results with the experimental report of Luong et al .…”

“…Our starting structures were build and visualized using the Molden and Weblab software. Each successive structure was produced by adding water molecules to the previous structure in various locations and by reproducing previously reported geometries . It is important to note that at n = 6, O 2 – (H 2 O) n clusters became increasingly complex and molecular dynamics calculations were then used to explore the potential energy surface at different temperatures, from 300 to 900 K, which provided enough thermal energy to overcome energy barriers.…”

“…performed an ab initio molecular dynamics study of O 2 – solvated in 31 water molecules and estimated that the average water coordination number was 4.5 . Tachikawa investigated the electron detachment dynamics of O 2 – (H 2 O) with an ab initio molecular dynamics approach . So far, the more comprehensive studies of O 2 – (H 2 O) n clusters are the theoretical report of Bork et al with their ab initio investigation of the structures and energetics for O 2 – (H 2 O) n molecular clusters, with n ≤ 12, and the experimental study by Sekimoto et al of O 2 – (H 2 O) n molecular clusters, with n ≤ 81 using mass spectromety …”

Direct ab‐initio molecular dynamics study on the radiation effects on catalytic triad composed of Ser‐His‐Glu residues

“…First, we assumed the CAS‐SCF/6‐31G(d) potential energy surface for the direct AIMD trajectory calculations. In previous papers, we investigated the reaction dynamics of several reaction systems using MP2 wave function. However, the MP2 wave function needs high cost, and was impossible to calculate the present catalytic triad because the present reaction system is very large for the MP2‐dynamics calculation.…”

“…The structure of the catalytic triad was optimized at the MP2/ 6-31111G(d,p) level of theory. The direct AIMD calculation [25][26][27] was carried out from the optimized structure of Ser-His-Glu. We used complete active space-self consistent field theory (CAS-SCF) to calculate electronic structures and multidimensional potential energy surface for the cation and anion systems.…”