Adsorption of water in Na-LTA zeolite : an Ab Initio Molecular Dynamics investigation

Author(s):  
Joharimanitra Randrianandraina ◽  
Michael Badawi ◽  
Bruno Cardey ◽  
Manuel Grivet ◽  
Jean-Emmanuel Groetz ◽  
...  

The very wide range of applications of LTA zeolites, including the storage of tritiated water, implies that a detailed and accurate atomic-scale description of the adsorption processes taking place in...

2020 ◽  
Author(s):  
Nicholas Humphrey ◽  
Selin Bac ◽  
Shaama Mallikarjun Sharada

<div> <div> <div> <p>We present a multi-scale modeling study of atomically dispersed Pt on the (110) surface of rutile TiO2. Using density functional theory (DFT) and ab initio molecular dynamics (AIMD), we probe the dynamic evolution of the catalytic surface at elevated temperatures. We identify metal atom diffusion as well as support atom mobility as important dynamical phenomena that enable the formation of new active sites. Among the eight new dynamically formed sites that are distinct from prior experimental and DFT reports, two sites exhibit anionic, near-linear O−Pt−O configurations. Such configurations are neither intuitive nor easily located using static methods such as DFT. Therefore, DFT alone is not sufficient to obtain a complete, dynamic description of the catalytic surface. Furthermore, the near-linear O−Pt−O sites exhibit CO binding characteristics that are markedly distinct from their parent sites, with possibly higher activity towards CO oxidation and water-gas shift reactions. Based on the wide range of adsorbate affinities exhibited by the DFT and AIMD-generated sites in this study, our aim going forward is to probe site-sensitivity of water-gas shift kinetics with these catalysts. </p> </div> </div> </div>


2020 ◽  
Author(s):  
Nicholas Humphrey ◽  
Selin Bac ◽  
Shaama Mallikarjun Sharada

<div> <div> <div> <p>We present a multi-scale modeling study of atomically dispersed Pt on the (110) surface of rutile TiO2. Using density functional theory (DFT) and ab initio molecular dynamics (AIMD), we probe the dynamic evolution of the catalytic surface at elevated temperatures. We identify metal atom diffusion as well as support atom mobility as important dynamical phenomena that enable the formation of new active sites. Among the eight new dynamically formed sites that are distinct from prior experimental and DFT reports, two sites exhibit anionic, near-linear O−Pt−O configurations. Such configurations are neither intuitive nor easily located using static methods such as DFT. Therefore, DFT alone is not sufficient to obtain a complete, dynamic description of the catalytic surface. Furthermore, the near-linear O−Pt−O sites exhibit CO binding characteristics that are markedly distinct from their parent sites, with possibly higher activity towards CO oxidation and water-gas shift reactions. Based on the wide range of adsorbate affinities exhibited by the DFT and AIMD-generated sites in this study, our aim going forward is to probe site-sensitivity of water-gas shift kinetics with these catalysts. </p> </div> </div> </div>


2019 ◽  
Author(s):  
Liqun Cao ◽  
Jinzhe Zeng ◽  
Mingyuan Xu ◽  
Chih-Hao Chin ◽  
Tong Zhu ◽  
...  

Combustion is a kind of important reaction that affects people's daily lives and the development of aerospace. Exploring the reaction mechanism contributes to the understanding of combustion and the more efficient use of fuels. Ab initio quantum mechanical (QM) calculation is precise but limited by its computational time for large-scale systems. In order to carry out reactive molecular dynamics (MD) simulation for combustion accurately and quickly, we develop the MFCC-combustion method in this study, which calculates the interaction between atoms using QM method at the level of MN15/6-31G(d). Each molecule in systems is treated as a fragment, and when the distance between any two atoms in different molecules is greater than 3.5 Å, a new fragment involved two molecules is produced in order to consider the two-body interaction. The deviations of MFCC-combustion from full system calculations are within a few kcal/mol, and the result clearly shows that the calculated energies of the different systems using MFCC-combustion are close to converging after the distance thresholds are larger than 3.5 Å for the two-body QM interactions. The methane combustion was studied with the MFCC-combustion method to explore the combustion mechanism of the methane-oxygen system.


2021 ◽  
Vol 22 (9) ◽  
pp. 4378
Author(s):  
Anna Helena Mazurek ◽  
Łukasz Szeleszczuk ◽  
Dariusz Maciej Pisklak

This review focuses on a combination of ab initio molecular dynamics (aiMD) and NMR parameters calculations using quantum mechanical methods. The advantages of such an approach in comparison to the commonly applied computations for the structures optimized at 0 K are presented. This article was designed as a convenient overview of the applied parameters such as the aiMD type, DFT functional, time step, or total simulation time, as well as examples of previously studied systems. From the analysis of the published works describing the applications of such combinations, it was concluded that including fast, small-amplitude motions through aiMD has a noticeable effect on the accuracy of NMR parameters calculations.


ACS Omega ◽  
2021 ◽  
Author(s):  
Khagendra Baral ◽  
Saro San ◽  
Ridwan Sakidja ◽  
Adrien Couet ◽  
Kumar Sridharan ◽  
...  

2021 ◽  
Vol 7 ◽  
pp. 111-119
Author(s):  
Ben Craig ◽  
Chris-Kriton Skylaris ◽  
Carlos Ponce de Leon ◽  
Denis Kramer

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