scholarly journals Ion pair particles at the air–water interface

2017 ◽  
Vol 114 (47) ◽  
pp. 12401-12406 ◽  
Author(s):  
Manoj Kumar ◽  
Joseph S. Francisco
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Methanesulfonic Acid ◽  
Density Functional Theory Calculations ◽  
Particle Formation ◽  
Ion Pair ◽  
Urban Environments ◽  
Water Interface ◽  
Air Water Interface ◽  
Dynamics Simulations

Although the role of methanesulfonic acid (HMSA) in particle formation in the gas phase has been extensively studied, the details of the HMSA-induced ion pair particle formation at the air–water interface are yet to be examined. In this work, we have performed Born–Oppenheimer molecular dynamics simulations and density functional theory calculations to investigate the ion pair particle formation from HMSA and (R1)(R2)NH (for NH3, R1= R2= H; for CH3NH2, R1= H and R2= CH3; and for CH3NH2, R1= R2= CH3) at the air–water interface. The results show that, at the air–water interface, HMSA deprotonates within a few picoseconds and results in the formation of methanesulfonate ion (MSA−)⋅⋅H3O+ion pair. However, this ion pair decomposes immediately, explaining why HMSA and water alone are not sufficient for forming stable particles in atmosphere. Interestingly, the particle formation from the gas-phase hydrogen-bonded complexes of HMSA with (R1)(R2)NH on the water droplet is observed with a few femtoseconds, suggesting a mechanism for the gas to particle conversion in aqueous environments. The reaction involves a direct proton transfer between HMSA and (R1)(R2)NH, and the resulting MSA−⋅⋅(R1)(R2)NH2+complex is bound by one to four interfacial water molecules. The mechanistic insights gained from this study may serve as useful leads for understanding about the ion pair particle formation from other precursors in forested and polluted urban environments.

Interaction of CO with Gold Under Gas Phase and Electrochemical Environments

2020 ◽  
Author(s):  
Sudarshan Vijay ◽  
Thomas Vagn Hogg ◽  
Johan Ehlers ◽  
Henrik Høgh Kristoffersen ◽  
Yu Katayama ◽  
...  
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Co Adsorption ◽  
Density Functional Theory Calculations ◽  
Underpotential Deposition ◽  
Attenuated Total Reflection ◽  
Ab Initio Molecular Dynamics ◽  
Adsorption Sites ◽  
Temperature Programmed ◽  
Dynamics Simulations

<div> <div> <div> <p>We present a joint theoretical-experimental study of CO coverage on Au under both gas phase and electrochemical conditions. By analyzing temperature programmed desorption (TPD) spectra on (211) and (310) surface facets, we show that, under atmospheric CO pressure, the steps of both facets adsorb up to 0.7 ML coverage of *CO, while the terraces have close to zero coverage. We show this result to be consistent with density functional theory calculations of adsorption energies. Under electrochemical conditions on polycrystalline Au, we investigate the CO binding with in situ attenuated total reflection surface enhanced IR spectra (ATR-SEIRAS). We detect a CO band at 0.2V vs. SHE that disappears upon partial Pb underpotential deposition (facet selective), which suggests Pb blocks the CO adsorption sites. With Pb underpotential deposition on single crystals and theoretical surface Pourbaix analysis, we narrow down the possible adsorption sites of CO to open site motifs: (211) and (110) steps, as well as (100) terraces. Ab initio molecular dynamics simulations of explicit water at the Au surface, however, shows the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace than steps in an electrochemical environment. The competition between water and CO adsorption can result in different binding sites for *CO on Au in gas phase and electrochemical environments. </p> </div> </div> </div>

scholarly journals Interaction of CO with Gold Under Gas Phase and Electrochemical Environments

2020 ◽  
Author(s):  
Sudarshan Vijay ◽  
Thomas Vagn Hogg ◽  
Johan Ehlers ◽  
Henrik Høgh Kristoffersen ◽  
Yu Katayama ◽  
...  
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Co Adsorption ◽  
Density Functional Theory Calculations ◽  
Underpotential Deposition ◽  
Attenuated Total Reflection ◽  
Ab Initio Molecular Dynamics ◽  
Adsorption Sites ◽  
Temperature Programmed ◽  
Dynamics Simulations

<div> <div> <div> <p>We present a joint theoretical-experimental study of CO coverage on Au under both gas phase and electrochemical conditions. By analyzing temperature programmed desorption (TPD) spectra on (211) and (310) surface facets, we show that, under atmospheric CO pressure, the steps of both facets adsorb up to 0.7 ML coverage of *CO, while the terraces have close to zero coverage. We show this result to be consistent with density functional theory calculations of adsorption energies. Under electrochemical conditions on polycrystalline Au, we investigate the CO binding with in situ attenuated total reflection surface enhanced IR spectra (ATR-SEIRAS). We detect a CO band at 0.2V vs. SHE that disappears upon partial Pb underpotential deposition (facet selective), which suggests Pb blocks the CO adsorption sites. With Pb underpotential deposition on single crystals and theoretical surface Pourbaix analysis, we narrow down the possible adsorption sites of CO to open site motifs: (211) and (110) steps, as well as (100) terraces. Ab initio molecular dynamics simulations of explicit water at the Au surface, however, shows the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace than steps in an electrochemical environment. The competition between water and CO adsorption can result in different binding sites for *CO on Au in gas phase and electrochemical environments. </p> </div> </div> </div>

A New Phase of the Na+ Ion Conductor Na3PS4

2019 ◽  
Author(s):  
Theodosios Famprikis ◽  
James Dawson ◽  
François Fauth ◽  
Emmanuelle Suard ◽  
Benoit Fleutot ◽  
...  
Keyword(s):  
Solid Electrolytes ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Ion Conductor ◽  
Solid State Batteries ◽  
Density Analysis ◽  
Two Phases ◽  
Dynamics Simulations

<div> <p>Solid electrolytes are crucial for next‑generation solid‑state batteries and Na<sub>3</sub>PS<sub>4</sub> is one of the most promising Na<sup>+</sup> conductors for such applications. At present, two phases of Na<sub>3</sub>PS<sub>4</sub> have been identified and it had been thought to melt above 500 °C. In contrast, we show that it remains solid above this temperature and transforms into a third polymorph, γ, exhibiting superionic behavior. We propose an orthorhombic crystal structure for γ‑Na<sub>3</sub>PS<sub>4</sub> based on scattering density analysis of diffraction data and density functional theory calculations. We show that the Na<sup>+</sup> superionic behavior is associated with rotational motion of the thiophosphate polyanions pointing to a rotor phase, based on <i>ab initio</i> molecular dynamics simulations and supported by high‑temperature synchrotron and neutron diffraction, thermal analysis and impedance spectroscopy. These findings are of importance for the development of new polyanion‑based solid electrolytes.</p> </div>

Graphene adlayer growth between nonepitaxial graphene and Ni(111) substrate: a promising theoretical scheme

2020 ◽  
Author(s):  
Lijuan Meng ◽  
Jinlian Lu ◽  
Yujie Bai ◽  
Lili Liu ◽  
Tang Jingyi ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Chemical Vapor Deposition ◽  
Molecular Dynamics Simulations ◽  
Vapor Deposition ◽  
Density Functional ◽  
Chemical Vapor ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Dynamics Simulations

Understanding the fundamentals of chemical vapor deposition bilayer graphene growth is crucial for its synthesis. By employing density functional theory calculations and classical molecular dynamics simulations, we have investigated the...

scholarly journals Molecular Insights into Cage Occupancy of Hydrogen Hydrate: A Computational Study

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 699 ◽  
Author(s):  
Ma ◽  
Zhong ◽  
Liu ◽  
Zhong ◽  
Yan ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Storage ◽  
Molecular Dynamics Simulations ◽  
Density Functional ◽  
Storage Capacity ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
Hydrogen Storage Capacity ◽  
Large Cage ◽  
Dynamics Simulations

Density functional theory calculations and molecular dynamics simulations were performed to investigate the hydrogen storage capacity in the sII hydrate. Calculation results show that the optimum hydrogen storage capacity is ~5.6 wt%, with the double occupancy in the small cage and quintuple occupancy in the large cage. Molecular dynamics simulations indicate that these multiple occupied hydrogen hydrates can occur at mild conditions, and their stability will be further enhanced by increasing the pressure or decreasing the temperature. Our work highlights that the hydrate is a promising material for storing hydrogen.

Behavior of β-Amyloid 1−16 at the Air−Water Interface at Varying pH by Nonlinear Spectroscopy and Molecular Dynamics Simulations

2011 ◽  
Vol 115 (23) ◽  
pp. 5873-5880 ◽  
Author(s):  
Abigail E. Miller ◽  
Poul B. Petersen ◽  
Christopher W. Hollars ◽  
Richard J. Saykally ◽  
Jan Heyda ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Nonlinear Spectroscopy ◽  
Water Interface ◽  
Air Water Interface ◽  
Β Amyloid ◽  
Dynamics Simulations

Molecular dynamics simulations predict an accelerated dissociation of H2CO3 at the air–water interface

2014 ◽  
Vol 16 (46) ◽  
pp. 25573-25582 ◽  
Author(s):  
Mirza Galib ◽  
Gabriel Hanna
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Carbonic Acid ◽  
Bulk Water ◽  
Water Interface ◽  
Air Water Interface ◽  
Dynamics Simulations ◽  
Dissociation Barrier

Ab initio molecular dynamics simulations of carbonic acid (H2CO3) at the air–water interface yield a lower dissociation barrier than in bulk water.

The Role of SiH3 Diffusion in Determining the Surface Smoothness of Plasma-Deposited Amorphous Si Thin Films: An Atomic-Scale Analysis

2005 ◽  
Vol 862 ◽  
Author(s):  
Mayur S. Valipa ◽  
Tamas Bakos ◽  
Eray S. Aydil ◽  
Dimitrios Maroudas
Keyword(s):  
Thin Films ◽  
Density Functional ◽  
Activation Barrier ◽  
Density Functional Theory Calculations ◽  
Atomic Scale ◽  
Functional Theory ◽  
Weak Adsorption ◽  
Dynamics Simulations ◽  
Hydrogenated Amorphous

AbstractDevice-quality hydrogenated amorphous silicon (a-Si:H) thin films grown under conditions where the SiH3 radical is the dominant deposition precursor are remarkably smooth, as the SiH3 radical is very mobile and fills surface valleys during its diffusion on the a-Si:H surface. In this paper, we analyze atomic-scale mechanisms of SiH3 diffusion on a-Si:H surfaces based on molecular-dynamics simulations of SiH3 radical impingement on surfaces of a-Si:H films. The computed average activation barrier for radical diffusion on a-Si:H is 0.16 eV. This low barrier is due to the weak adsorption of the radical onto the a-Si:H surface and its migration predominantly through overcoordination defects; this is consistent with our density functional theory calculations on crystalline Si surfaces. The diffusing SiH3 radical incorporates preferentially into valleys on the a-Si:H surface when it transfers an H atom and forms a Si-Si backbond, even in the absence of dangling bonds.

scholarly journals Formation and reactions of the 1, 8-naphthyridine (napy) ligated geminally dimetallated phenyl complexes [(napy)Cu2(Ph)]+, [(napy)Ag2(Ph)]+ and [(napy)CuAg(Ph)]+

2019 ◽  
Vol 25 (1) ◽  
pp. 30-43 ◽  
Author(s):  
Qiuyan Jin ◽  
Jiaye Li ◽  
Alireza Ariafard ◽  
Allan J Canty ◽  
Richard AJ O’Hair
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Ion Trap ◽  
Density Functional Theory Calculations ◽  
Collision Induced Dissociation ◽  
Ion Trap Mass Spectrometry ◽  
Functional Theory ◽  
Organometallic Cations ◽  
Gas Phase Ion

Gas-phase ion trap mass spectrometry experiments and density functional theory calculations have been used to examine the routes to the formation of the 1,8-naphthyridine (napy) ligated geminally dimetallated phenyl complexes [(napy)Cu2(Ph)]+, [(napy)Ag2(Ph)]+ and [(napy)CuAg(Ph)]+ via extrusion of CO2 or SO2 under collision-induced dissociation conditions from their corresponding precursor complexes [(napy)Cu2(O2CPh)]+, [(napy)Ag2(O2CPh)]+, [(napy)CuAg(O2CPh)]+ and [(napy)Cu2(O2SPh)]+, [(napy)Ag2(O2SPh)]+, [(napy)CuAg(O2SPh)]+. Desulfination was found to be more facile than decarboxylation. Density functional theory calculations reveal that extrusion proceeds via two transition states: TS1 enables isomerization of the O, O-bridged benzoate to its O-bound form; TS2 involves extrusion of CO2 or SO2 with the concomitant formation of the organometallic cation and has the highest barrier. Of all the organometallic cations, only [(napy)Cu2(Ph)]+ reacts with water via hydrolysis to give [(napy)Cu2(OH)]+, consistent with density functional theory calculations which show that hydrolysis proceeds via the initial formation of the adduct [(napy)Cu2(Ph)(H2O)]+ which then proceeds via TS3 in which the coordinated H2O is deprotonated by the coordinated phenyl anion to give the product complex [(napy)Cu2(OH)(C6H6)]+, which then loses benzene.

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