Ab initio mechanism revealing for tricalcium silicate dissolution

2021 ◽  
Author(s):  
Yunjian Li ◽  
Hui Pan ◽  
Xing Ming ◽  
Zongjin Li
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Calcium Ions ◽  
Tricalcium Silicate ◽  
Proton Exchange ◽  
Reaction Pathways ◽  
Ab Initio Molecular Dynamics ◽  
Energy Barriers ◽  
Silicate Dissolution ◽  
Quantitative Analyses

Abstract Dissolution of mineral in water is ubiquitous in nature and industry, especially for the calcium silicate species. However, the behavior of such a complex chemical reaction is still unclear at atomic level. Here, we show that the ab initio molecular dynamics and metadynamics simulations enable quantitative analyses of reaction pathways, and the thermodynamics and kinetics of calcium ion dissolution from the tricalcium silicate (Ca3SiO5) surface. The calcium sites with different coordination environment leads to different reaction pathways and free energy barriers. The low free energy barriers lead to that the detachment of calcium ions is a ligand exchange and auto-catalytic process. Moreover, the water adsorption, proton exchange and diffusion of water into the surface layer accelerate the leaching of calcium ions from the surface step by step. The discovery in this work thus would be a landmark for revealing the mechanism of cement hydration.

Microscopic mechanisms of initial oxidation of Si(100): Reaction pathways and free-energy barriers

2012 ◽  
Vol 85 (20) ◽  
Author(s):  
Kenichi Koizumi ◽  
Mauro Boero ◽  
Yasuteru Shigeta ◽  
Atsushi Oshiyama
Keyword(s):  
Free Energy ◽  
Reaction Pathways ◽  
Energy Barriers ◽  
Initial Oxidation

scholarly journals OH− and H3O+ Diffusion in Model AEMs and PEMs at Low Hydration: Insights from Ab Initio Molecular Dynamics

Membranes ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 355
Author(s):  
Tamar Zelovich ◽  
Mark E. Tuckerman
Keyword(s):  
Molecular Dynamics ◽  
Fuel Cell ◽  
Ab Initio ◽  
Cost Effective ◽  
Clean Energy ◽  
Proton Exchange ◽  
Ab Initio Molecular Dynamics ◽  
Anion Exchange Membranes ◽  
Diffusion Mechanisms ◽  
Dynamics Simulations

Fuel cell-based anion-exchange membranes (AEMs) and proton exchange membranes (PEMs) are considered to have great potential as cost-effective, clean energy conversion devices. However, a fundamental atomistic understanding of the hydroxide and hydronium diffusion mechanisms in the AEM and PEM environment is an ongoing challenge. In this work, we aim to identify the fundamental atomistic steps governing hydroxide and hydronium transport phenomena. The motivation of this work lies in the fact that elucidating the key design differences between the hydroxide and hydronium diffusion mechanisms will play an important role in the discovery and determination of key design principles for the synthesis of new membrane materials with high ion conductivity for use in emerging fuel cell technologies. To this end, ab initio molecular dynamics simulations are presented to explore hydroxide and hydronium ion solvation complexes and diffusion mechanisms in the model AEM and PEM systems at low hydration in confined environments. We find that hydroxide diffusion in AEMs is mostly vehicular, while hydronium diffusion in model PEMs is structural. Furthermore, we find that the region between each pair of cations in AEMs creates a bottleneck for hydroxide diffusion, leading to a suppression of diffusivity, while the anions in PEMs become active participants in the hydronium diffusion, suggesting that the presence of the anions in model PEMs could potentially promote hydronium diffusion.

scholarly journals Synergistic adsorptions of Na2CO3 and Na2SiO3 on calcium minerals revealed by spectroscopic and ab initio molecular dynamics studies

2019 ◽  
Vol 10 (43) ◽  
pp. 9928-9940 ◽  
Author(s):  
Yann Foucaud ◽  
Michaël Badawi ◽  
Lev O. Filippov ◽  
Odile Barres ◽  
Inna V. Filippova ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Sodium Silicate ◽  
Sodium Carbonate ◽  
Proton Exchange ◽  
Ab Initio Molecular Dynamics ◽  
Calcium Minerals

FTIR, XPS, and ab initio molecular dynamics studies demonstrated that sodium silicate (Na2SiO3) adsorbs on fluorite with a higher affinity when they are treated beforehand by sodium carbonate (Na2CO3) due to proton exchange(s).

scholarly journals Water Dipole and Quadrupole Moment Contributions to the Ion Hydration Free Energy by the Deep Neural Network Trained with Ab Initio Molecular Dynamics Data

2020 ◽  
Author(s):  
YU SHI ◽  
Carrie C. Doyle ◽  
Thomas L. Beck
Keyword(s):  
Neural Network ◽  
Molecular Dynamics ◽  
Free Energy ◽  
Ab Initio ◽  
Deep Neural Network ◽  
Ab Initio Molecular Dynamics ◽  
Quadrupole Moments ◽  
Hydration Free Energy ◽  
Ion Hydration ◽  
Water Dipole

<div>We report a calculation scheme on water molecular dipole and quadrupole moments in the liquid phase through a Deep Neural Network (DNN) model. Employing the the Maximally Localized Wannier Functions (MLWF) for the valence electrons, we obtain the water moments through a post-process on trajectories from \textit{ab-initio} molecular dynamics (AIMD) simulations at the density functional theory (DFT) level. In the framework of the deep potential molecular dynamics (DPMD), we develop a scheme to train a DNN with the AIMD moments data. Applying the model, we calculate the contributions from water dipole and quadrupole moments to the electrostatic potential at the center of a cavity of radius 4.1 \AA\ as -3.87 V, referenced to the average potential in the bulk-like liquid region.</div><div>To unravel the ion-independent water effective local potential contribution to the ion hydration free energy, we estimate the 3rd cumulant term as -0.22 V from simulations totally over 6 ns, a time-scale inaccessible for AIMD calculations. </div>

scholarly journals Mechanisms and competition of halide substitution and hydrolysis in reactions of N2O5 with seawater

2019 ◽  
Vol 5 (6) ◽  
pp. eaav6503 ◽  
Author(s):  
Laura M. McCaslin ◽  
Mark A. Johnson ◽  
R. Benny Gerber
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Time Scales ◽  
Atmospheric Chemistry ◽  
Theoretical Study ◽  
Reaction Pathways ◽  
Ab Initio Molecular Dynamics ◽  
Central Importance ◽  
Key Features ◽  
Hydrolysis Of

SN2-type halide substitution and hydrolysis are two of the most ubiquitous reactions in chemistry. The interplay between these processes is fundamental in atmospheric chemistry through reactions of N2O5 and seawater. N2O5 plays a major role in regulating levels of O3, OH, NOx, and CH4. While the reactions of N2O5 and seawater are of central importance, little is known about their mechanisms. Of interest is the activation of Cl in seawater by the formation of gaseous ClNO2, which occurs despite the fact that hydrolysis (to HNO3) is energetically more favorable. We determine key features of the reaction landscape that account for this behavior in a theoretical study of the cluster N2O5/Cl−/H2O. This was carried out using ab initio molecular dynamics to determine reaction pathways, structures, and time scales. While hydrolysis of N2O5 occurs in the absence of Cl−, results here reveal that a low-lying pathway featuring halide substitution intermediates enhances hydrolysis.

Rate Coefficients for Intramolecular Homolytic Substitution of Oxyacyl Radicals at Sulfur

2013 ◽  
Vol 66 (3) ◽  
pp. 323 ◽  
Author(s):  
Heather M. Aitken ◽  
Sonia M. Horvat ◽  
Michelle L. Coote ◽  
Ching Yeh Lin ◽  
Carl H. Schiesser
Keyword(s):  
Free Energy ◽  
Ab Initio ◽  
Gas Phase ◽  
Sulfur Atom ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Rate Coefficients ◽  
Energy Barriers ◽  
Tert Butyl ◽  
Homolytic Substitution

It is predicted on the basis of ab initio and density functional calculations that intramolecular homolytic substitution of oxyacyl radicals at the sulfur atom in ω-alkylthio-substituted radicals do not involve hypervalent intermediates. With tert-butyl as the leaving radical, free energy barriers ΔG‡ (G3(MP2)-RAD) for these reactions range from 45.8 kJ mol–1 for the formation of the five-membered cyclic thiocarbonate (8) to 56.7 kJ mol–1 for the formation of the six-membered thiocarbonate (9). Rate coefficients in the order of 104–106 s–1 and 101–104 s–1 for the formation of 8 and 9, respectively, at 353.15 K in the gas phase are predicted at the G3(MP2)-RAD level of theory.

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