scholarly journals Defect Formation, T-Atom Substitution and Adsorption of Guest Molecules in MSE-Type Zeolite Framework—DFT Modeling

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7296
Author(s):  
Petko St. Petkov ◽  
Kristina Simeonova ◽  
Iskra Z. Koleva ◽  
Hristiyan A. Aleksandrov ◽  
Yoshihiro Kubota ◽  
...  
Keyword(s):  
Density Functional ◽  
Defect Formation ◽  
Dissociative Adsorption ◽  
Zeolite Framework ◽  
Functional Theory ◽  
Guest Molecules ◽  
Dft Modeling ◽  
Type Zeolite ◽  
Modeling Of Adsorption ◽  
Atom Position

We used computational modeling, based on Density Functional Theory, to help understand the preference for the formation of silanol nests and the substitution of Si by Ti or Al in different crystallographic positions of the MSE-type framework. All these processes were found to be energetically favorable by more than 100 kJ/mol. We suggested an approach for experimental identification of the T atom position in Ti-MCM-68 zeolite via simulation of infrared spectra of pyridine and acetonitrile adsorption at Ti. The modeling of adsorption of hydrogen peroxide at Ti center in the framework has shown that the molecular adsorption was preferred over the dissociative adsorption by 20 to 40 kJ/mol in the presence or absence of neighboring T-atom vacancy, respectively.

Density functional theory study into H2O dissociative adsorption on the Fe5C2(010) surface

2013 ◽  
Vol 468 ◽  
pp. 370-383 ◽  
Author(s):  
Rui Gao ◽  
Dong-Bo Cao ◽  
Shaoli Liu ◽  
Yong Yang ◽  
Yong-Wang Li ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Dissociative Adsorption ◽  
Density Functional Theory Study ◽  
Functional Theory

Aluminum distribution in mordenite-zeolite framework: A new outlook based on density functional theory calculations

2021 ◽  
pp. 122725
Author(s):  
Joel Antúnez-García ◽  
D.H. Galván ◽  
Vitalii Petranovskii ◽  
Fabian N. Murrieta-Rico ◽  
Rosario I. Yocupicio-Gaxiola ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Zeolite Framework ◽  
Functional Theory ◽  
Aluminum Distribution

A complete ab initio thermodynamic and kinetic catalogue of the defect chemistry of hematite α-Fe2O3, its cation diffusion, and sample donor dopants

2021 ◽  
Author(s):  
Shehab Shousha ◽  
Sarah Khalil ◽  
Mostafa Youssef
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Defect Formation ◽  
Defect Chemistry ◽  
Cation Diffusion ◽  
Functional Theory ◽  
Migration Barriers ◽  
Hubbard U ◽  
And Migration ◽  
Formation Energies

This paper studies comprehensively the defect chemistry and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U...

scholarly journals Theoretical Investigation of the Fusion Process of Mono-Cages to Tri-Cages with CH4/C2H6 Guest Molecules in sI Hydrates

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7071
Author(s):  
Shuxian Wei ◽  
Siyuan Liu ◽  
Shoufu Cao ◽  
Sainan Zhou ◽  
Yong Chen ◽  
...  
Keyword(s):  
Natural Gas ◽  
Density Functional ◽  
Fusion Energy ◽  
Fusion Process ◽  
Large Cage ◽  
Cage Structure ◽  
Microscopic Mechanism ◽  
Functional Theory ◽  
Guest Molecules ◽  
Further Development

Owing to a stable and porous cage structure, natural gas hydrates can store abundant methane and serve as a potentially natural gas resource. However, the microscopic mechanism of how hydrate crystalline grows has not been fully explored, especially for the structure containing different guest molecules. Hence, we adopt density functional theory (DFT) to investigate the fusion process of structure I hydrates with CH4/C2H6 guest molecules from mono-cages to triple-cages. We find that the volume of guest molecules affects the stabilities of large (51262, L) and small (512, s) cages, which are prone to capture C2H6 and CH4, respectively. Mixed double cages (small cage and large cage) with the mixed guest molecules have the highest stability and fusion energy. The triangular triple cages exhibit superior stability because of the three shared faces, and the triangular mixed triple cages (large-small-large) structure with the mixed guest molecules shows the highest stability and fusion energy in the triple-cage fusion process. These results can provide theoretical insights into the growth mechanism of hydrates with other mono/mixed guest molecules for further development and application of these substances.

scholarly journals Supramolecular Complexes of Cucurbiturils with Second Group Metal Salts and Hydrates and Histamine

INEOS OPEN ◽  
2021 ◽  
Vol 4 ◽  
Author(s):  
Yu. A. Borisov ◽  
◽  
S. S. Kiselev ◽  
Keyword(s):  
Aqueous Solution ◽  
Density Functional Theory ◽  
Density Functional ◽  
Metal Salts ◽  
Supramolecular Complexes ◽  
Water Molecules ◽  
Functional Theory ◽  
Guest Molecules ◽  
First Time ◽  
Formation Energies

The interaction of cucurbiturils (Q6, Q7, and Q8) with Ca and Ba chlorides and iodides are studied for the first time by density functional theory. The thermodynamic parameters for the formation of host–guest complexes are calculated. The structures of complexes of Q6 and Q7 with one and two guest molecules are established. The energy parameters for the transfer of Be2+ and Ba2+ cations from an aqueous solution into the cavity of Q7 containing n water molecules are defined. The dependences of the formation energies for complexes Q7WnBe2+ and Q7WnBa2+ on the number of water molecules are shown to be parabolic, with the energy minima at n = 5 and n = 6, respectively. It is found that Q7 can form in an aqueous solution supramolecular complexes with protonated histamine (HA) and neutral histamine in the presence of Ca2+ ions.

scholarly journals DFT Visualization and Experimental Evidence of BHT-Mg-Catalyzed Copolymerization of Lactides, Lactones and Ethylene Phosphates

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1641 ◽  
Author(s):  
Ilya Nifant’ev ◽  
Andrey Shlyakhtin ◽  
Maxim Kosarev ◽  
Dmitry Gavrilov ◽  
Stanislav Karchevsky ◽  
...  
Keyword(s):  
Ring Opening ◽  
Density Functional ◽  
Point Of View ◽  
Basis Set ◽  
Random Copolymers ◽  
Key Factors ◽  
Functional Theory ◽  
Cyclic Esters ◽  
Dft Modeling ◽  
Derivatives Of

Catalytic ring-opening polymerization (ROP) of cyclic esters (lactides, lactones) and cyclic ethylene phosphates is an effective way to process materials with regulated hydrophilicity and controlled biodegradability. Random copolymers of cyclic monomers of different chemical nature are highly attractive due to their high variability of characteristics. Aryloxy-alkoxy complexes of non-toxic metals such as derivatives of 2,6-di-tert-butyl-4-methylphenoxy magnesium (BHT-Mg) complexes are effective coordination catalysts for homopolymerization of all types of traditional ROP monomers. In the present paper, we report the results of density functional theory (DFT) modeling of BHT-Mg-catalyzed copolymerization for lactone/lactide, lactone/ethylene phosphate and lactide/ethylene phosphate mixtures. ε-Caprolactone (ε-CL), l-lactide (l-LA) and methyl ethylene phosphate (MeOEP) were used as examples of monomers in DFT simulations by the Gaussian-09 program package with the B3PW91/DGTZVP basis set. Both binuclear and mononuclear reaction mechanistic concepts have been applied for the calculations of the reaction profiles. The results of calculations predict the possibility of the formation of random copolymers based on l-LA/MeOEP, and substantial hindrance of copolymerization for ε-CL/l-LA and ε-CL/MeOEP pairs. From the mechanistic point of view, the formation of highly stable five-membered chelate by the products of l-LA ring-opening and high donor properties of phosphates are the key factors that rule the reactions. The results of DFT modeling have been confirmed by copolymerization experiments.

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