AB Initio Simulation on Grotthuss Mechanism

2005 ◽  
Author(s):  
Jiahua Han ◽  
Hongtan Liu
Keyword(s):  
Ab Initio ◽  
Water Clusters ◽  
Dominant Role ◽  
High Mobility ◽  
Weight Fraction ◽  
Solvation Shell ◽  
Water Molecules ◽  
Proton Diffusion ◽  
Ab Initio Simulations ◽  
Grotthuss Mechanism

Ab initio simulations on Grotthuss mechanism have been carried out. Using the simulation results together with the existing experimental data, all the popular propositions for Grotthuss mechanism, including the one recently proposed by Noam [1], have been checked. Combining with the charge distribution calculation and the movement of the positive charge center inside the protonated water cluster during the proton diffusion process, only one mechanism is shown probable, while all the other proposed mechanisms are excluded. According to this probable mechanism, the high mobility of proton inside water is caused by the high diffusion rate of H5O2+, while the diffusion of H5O2+ is mainly induced by the thermal movement of water molecules at the second solvation shell of H5O2+ cation and the Zundel polarization inside the cation ion. Furthermore, the external field and thermo-dynamic effects play important roles during the transport process by affecting the reorientation of water molecules at the neighborhood of the second solvation shell of H5O2+ to induce the Zundel polarization and by providing the energy for the cleavage of the hydrogen bond between a newly formed water molecule and H5O2+. Because the weight (fraction) of H5O2+ among protonated water clusters decreases as temperature increases, this proposed mechanism is considered to play the dominant role only when temperature is below 572 K, above which, protons transport by other mechanisms become dominant.

scholarly journals Pseudo Jahn−Teller Origin of the Proton Tunneling in Zundel Cation Containing Water Clusters

2021 ◽  
Vol 57 (11) ◽  
pp. 1149
Author(s):  
I. Geru ◽  
N. Gorinchoy ◽  
I. Balan
Keyword(s):  
Ab Initio ◽  
Electronic Structures ◽  
Water Clusters ◽  
Electronic States ◽  
Adiabatic Potential ◽  
Water Molecules ◽  
High Symmetry ◽  
Proton Tunneling ◽  
Jahn Teller ◽  
Low Symmetry

The pseudo Jahn–Teller (PJT) origin of the proton transfer barrier in the Zundel cation at different O–O distances and in an H5O2+(H2O)4 cluster is revealed by means of  ab initio calculations of their electronic structures and the adiabatic potential energy curves. The vibronic constants in this approach were estimated by fitting the ab initio calculated adiabatic potential to its analytical expression. It is shown also that the high-symmetry nuclear configurations ofproton-centered water clusters of the type H+(H2O)n (n = 6, 4, 3) are unstable with respect to the low-symmetry nuclear distortions leading to forming the dihydronium cation H5O2+ and the appropriate number of water molecules: H2n + 1On+ →  (n – 2)H2O + H5O2+. The reason for this instability and the subsequent decay is the PJT coupling between the ground and excited electronic states.

scholarly journals Ab-Initio Computational Study on Fe2NiP schreibersite: Bulk and Surface Characterization

2021 ◽  
Author(s):  
Stefano Pantaleone ◽  
Marta Corno ◽  
Albert Rimola ◽  
Nadia Balucani ◽  
Piero Ugliengo
Keyword(s):  
Ab Initio ◽  
Surface Characterization ◽  
Organic Molecules ◽  
Computational Study ◽  
Water Molecules ◽  
Ab Initio Simulations ◽  
Iron Nickel ◽  
Living Organisms ◽  
Phosphorous Compounds ◽  
Simple Interaction

<p>Phosphorous is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorous is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and non-reactive materials, and, accordingly, unavailable for being readily incorporated in living organisms. A possible source of phosphorous is from the exogenous meteoritic bombardment and, in particular, in iron/nickel phosphites. These materials, by simple interaction with water, produce oxygenated phosphorous compounds, which can easily react with organic molecules, thus forming C-O-P bonds. In the present work, periodic ab-initio simulations at PBE level (inclusive of dispersive interactions) have been carried out on metallic Fe<sub>2</sub>NiP-schreibersite, as a relative abundant component of metallic meteorites, in order to characterize structural, energetics and vibrational properties of both bulk and surfaces of this material. The aim is to study the relative stability among different surfaces, to characterize both the nanocrystal morphology and the reactivity towards water molecules. </p>

scholarly journals Ab-Initio Computational Study on Fe2NiP Schreibersite: Bulk and Surface Characterization

2021 ◽  
Author(s):  
Stefano Pantaleone ◽  
Marta Corno ◽  
Albert Rimola ◽  
Nadia Balucani ◽  
Piero Ugliengo
Keyword(s):  
Ab Initio ◽  
Surface Characterization ◽  
Organic Molecules ◽  
Computational Study ◽  
Water Molecules ◽  
Ab Initio Simulations ◽  
Iron Nickel ◽  
Living Organisms ◽  
Phosphorous Compounds ◽  
Simple Interaction

<p>Phosphorous is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorous is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and non-reactive materials, and, accordingly, unavailable for being readily incorporated in living organisms. A possible source of phosphorous is from the exogenous meteoritic bombardment and, in particular, in iron/nickel phosphites. These materials, by simple interaction with water, produce oxygenated phosphorous compounds, which can easily react with organic molecules, thus forming C-O-P bonds. In the present work, periodic ab-initio simulations at PBE level (inclusive of dispersive interactions) have been carried out on metallic Fe<sub>2</sub>NiP-schreibersite, as a relative abundant component of metallic meteorites, in order to characterize structural, energetics and vibrational properties of both bulk and surfaces of this material. The aim is to study the relative stability among different surfaces, to characterize both the nanocrystal morphology and the reactivity towards water molecules. </p>

The hydration mechanism of ketene: 15 years later

1999 ◽  
Vol 77 (5-6) ◽  
pp. 817-829 ◽  
Author(s):  
Minh Tho Nguyen ◽  
Greet Raspoet
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Water Clusters ◽  
Field Method ◽  
Polarizable Continuum Model ◽  
Water Molecules ◽  
Orbital Theory ◽  
Acid Product ◽  
Reaction Field ◽  
Hydration Mechanism

New insights into the detailed mechanism of the hydration of ketene yielding acetic acid (H2C=C=O + H2O →> CH3COOH) were obtained by theoretical methods in both gas phase and solution. While gas phase calculations were performed using ab initio molecular orbital theory, bulk solvent effects were included using the self-consistent reaction field method (SCRF) and the polarizable continuum model (PCM). The hydration modeled by attack of water clusters containing two, three, and four water molecules confirms that a two-step addition of water to the ketene C=O bond, yielding a 1,1-enediol intermediate as initially demonstrated in 1984, is energetically, slightly but consistently, preferred over a concerted addition across the C=C bond leading directly to the acid product. Attempts to locate a zwitterion intermediate in solution were not successful. At least a cluster of three hydrogen-bonded water molecules is present in the gas phase supersystem to facilitate the proton transfer. Further incorporation of active water molecules in the catalytic water chain induces rather minor energetic improvements on the proton relay, which indicates a certain saturation of the cluster when reaching 3-4 water molecules. Effects of the surrounding solvent bulk do not change qualitatively the facts found in gas phase. The C=O addition mechanism is in better agreement with recent experimental developments in identifying enols of carboxylic acids than other mechanisms involving either a zwitterion or a direct C=C addition, as proposed for years in the literature.Key words: ketene, ketene hydration, hydration mechanism, solvent effect, ab initio calculations.

scholarly journals Ab-Initio Computational Study on Fe2NiP Schreibersite: Bulk and Surface Characterization

2021 ◽  
Author(s):  
Stefano Pantaleone ◽  
Marta Corno ◽  
Albert Rimola ◽  
Nadia Balucani ◽  
Piero Ugliengo
Keyword(s):  
Ab Initio ◽  
Surface Characterization ◽  
Organic Molecules ◽  
Computational Study ◽  
Water Molecules ◽  
Ab Initio Simulations ◽  
Iron Nickel ◽  
Living Organisms ◽  
Phosphorous Compounds ◽  
Simple Interaction

<p>Phosphorous is ubiquitous in planet Earth and plays a fundamental role in all living systems. Finding a reasonable prebiotic source of phosphorous is not trivial, as common sources where it is present nowadays are in the form of phosphate minerals, which are rather insoluble and non-reactive materials, and, accordingly, unavailable for being readily incorporated in living organisms. A possible source of phosphorous is from the exogenous meteoritic bombardment and, in particular, in iron/nickel phosphites. These materials, by simple interaction with water, produce oxygenated phosphorous compounds, which can easily react with organic molecules, thus forming C-O-P bonds. In the present work, periodic ab-initio simulations at PBE level (inclusive of dispersive interactions) have been carried out on metallic Fe<sub>2</sub>NiP-schreibersite, as a relative abundant component of metallic meteorites, in order to characterize structural, energetics and vibrational properties of both bulk and surfaces of this material. The aim is to study the relative stability among different surfaces, to characterize both the nanocrystal morphology and the reactivity towards water molecules. </p>

A model calculation on structures and excitation energies of the hydrated electron

1993 ◽  
Vol 71 (1) ◽  
pp. 118-124 ◽  
Author(s):  
Hiroto Tachikawa ◽  
Anders Lund ◽  
Masaaki Ogasawara
Keyword(s):  
Excitation Energy ◽  
Ab Initio ◽  
Short Range ◽  
Solvation Shell ◽  
Hydrated Electron ◽  
Excess Electron ◽  
Water Molecules ◽  
Range Interaction ◽  
Model Calculations ◽  
Ab Initio Mo

Model calculations were made on the hydrated electron by using the ab initio MO method combined with the MR-SD-Cl method and the coupled cluster theory. The models used in the calculations were water clusters denoted by [e−(H2O)n(H2O)m], where n = 2,3,4, and 6 for the first solvation shell and m = 0–28 for the second and third solvation shells. In these model calculations, the interactions between the excess electron and the water molecules in the first solvation shell are explicitly calculated by ab initio MO methods and the water molecules in the second and third solvation shells were represented by the fractional charges obtained at the MP2/D95V** level. The stabilization energies and the solvation radius r(e−–O), in terms of the distance between the center of the cavity and an oxygen atom of the surrounding water molecules, increased monotonically with the number of water molecules in the first solvation shell. On the other hand, the first excitation energy was not dependent on the number of water molecules in solvation shells, but constant, with the value of ca. 2.0 eV. On the basis of the present calculations, we suggest that (1) the energetic stability of excess electrons depends on both short-range interaction and long-range interaction, (2) the first excitation energy is critically affected by only the short-range interactions, and the excitation is theoretically attributed to the1s→2p transition of the excess electron.

Quantum Mechanical Interpretation of the Ultra-Low Energy Methyl-Rotation Dynamics in Porous Metal-Organic Frameworks Probed by Low-Frequency Vibrational Spectroscopy and ab initio Simulations

2018 ◽  
Author(s):  
Qi Li ◽  
Adam J. Zaczek ◽  
Timothy M. Korter ◽  
J. Axel Zeitler ◽  
Michael T. Ruggiero
Keyword(s):  
Ab Initio ◽  
Metal Organic Frameworks ◽  
Low Frequency ◽  
Rotor Dynamics ◽  
Quantum Mechanical ◽  
Valuable Insight ◽  
Void Space ◽  
Ab Initio Simulations ◽  
Metal Organic ◽  
Insight Into

<div>Understanding the nature of the interatomic interactions present within the pores of metal-organic frameworks</div><div>is critical in order to design and utilize advanced materials</div><div>with desirable applications. In ZIF-8 and its cobalt analogue</div><div>ZIF-67, the imidazolate methyl-groups, which point directly</div><div>into the void space, have been shown to freely rotate - even</div><div>down to cryogenic temperatures. Using a combination of ex-</div><div>perimental terahertz time-domain spectroscopy, low-frequency</div><div>Raman spectroscopy, and state-of-the-art ab initio simulations,</div><div>the methyl-rotor dynamics in ZIF-8 and ZIF-67 are fully charac-</div><div>terized within the context of a quantum-mechanical hindered-</div><div>rotor model. The results lend insight into the fundamental</div><div>origins of the experimentally observed methyl-rotor dynamics,</div><div>and provide valuable insight into the nature of the weak inter-</div><div>actions present within this important class of materials.</div>

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