scholarly journals ENERGIES AND VIBRATIONAL MODES OF SPECIES FORMED BY DEHYDROGENATION OF CH4 IN PRESENCE OF O2 OVER Cr2O3(0001)

Anales AFA ◽  
2021 ◽  
Vol 32 (3) ◽  
pp. 83-87
Author(s):  
S.N. Hernández Guiance ◽  
◽  
I.D. Coria ◽  
I.M. Irurzun ◽  
◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Experimental Methods ◽  
Vibrational Modes ◽  
Functional Theory ◽  
Methanol Formation ◽  
Dissociative States ◽  
Dissociative State ◽  
Good Agreement

In this work we perform a theoretical study of dehydrogenation process of CH4 on O2– in both molecular and dissociative states - previously adsorbed on Cr2O3(0001). Calculations are based on Density Functional Theory (DFT). The results show the methanol formation form the adsorption of CH4 on O2 in dissociative state with a formationenergy5:14 eV. Also formaldehyde was formed by the reaction of CH2with molecular O2(Eads=6:09 eV) and dioxymethylene by the reaction of CH2with O2 previously adsorbed in dissociative state on Cr2O3(0001), withEads=8:17 eV. Finally, the vibrational modes found by DFT for each of the species were compared, which are in good agreement with those of reference bibliography. This allows us to support the values found both by technical calculations and by experimental methods.

scholarly journals Theoretical Study on Structure and Electronic Properties of 4H-Cyclopenta[2,1-b,3;4-b’]dithiopene S-oxide and Its CCl2 and CF2 Bridged Derivatives

2015 ◽  
Vol 15 (1) ◽  
pp. 93-100 ◽  
Author(s):  
Banjo Semire ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Quantum Chemical ◽  
Density Functional ◽  
Theoretical Study ◽  
Functional Theory ◽  
Td Dft ◽  
Moller Plesset ◽  
Semi Empirical ◽  
Good Agreement

Quantum chemical calculations using semi-empirical, ab initio, density functional theory (DFT) and Møller plesset (MP2) methods were performed on 4H-Cyclopenta[2,1-b,3;4-b’]dithiopene S-oxide derivatives (i.e. bridged dithiophene S-oxides, BTOs). The geometries, stabilities, electronic and thermodynamic properties of the compounds were studied. The thermodynamic parameters calculated at PM3 were in good agreement with those calculated at B3LYP/6-31G(d) level. The band gap energies calculated at B3LYP/6-31G(d) level for the BTOs were lower than the un-substituted trithiophene but higher than 4H-Cyclopenta[2,1-b,3;4-b’]dithiopene. The absorption λmax calculated using TD-DFT was shifted to longer wavelength by successive replacement of methylene hydrogens of BTO by chlorine and fluorine atoms.

scholarly journals First principles calculations of the electronic and dielectric properties of λ-Ta2O5

TecnoLógicas ◽  
2018 ◽  
Vol 21 (43) ◽  
pp. 43-52 ◽  
Author(s):  
Camilo Valencia-Balvín ◽  
Santiago Pérez-Walton ◽  
Jorge M. Osorio-Guillén
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Study ◽  
Wide Bandgap ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Wide Bandgap Semiconductor ◽  
Exchange Correlation ◽  
Good Agreement

Ta2O5 is a wide-bandgap semiconductor that offers interesting applications in microwavecommunications, mainly related to the manufacture of filters and resonators whosesize is inversely proportional to the dielectric constant of the material. For that reason, inthis work we present a theoretical study, based on density functional theory (using PBEsoland hybrid HSE06 exchange-correlation functionals), of the electronic and dielectricproperties of the orthorhombic model -Ta2O5. We found that this model has a direct gap of2.09 and 3.7 eV with PBEsol and HSE06, respectively. Furthermore, the calculated staticdielectric constant, 51, is in good agreement with the reported values of other phases of thissemiconductor.

scholarly journals Theoretical study of the adsorption of benzene on coinage metals

2014 ◽  
Vol 10 ◽  
pp. 1775-1784 ◽  
Author(s):  
Werner Reckien ◽  
Melanie Eggers ◽  
Thomas Bredow
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Dispersion Correction ◽  
Functional Theory ◽  
Coinage Metals ◽  
Adsorption Energies ◽  
Theoretical Results ◽  
Good Agreement

The adsorption of benzene on the M(111), M(100) and M(110) surfaces of the coinage metals copper (M = Cu), silver (M = Ag) and gold (M = Au) is studied on the basis of density functional theory (DFT) calculations with an empirical dispersion correction (D3). Variants of the Perdew–Burke–Ernzerhof functionals (PBE, RPBE and RevPBE) in combination with different versions of the dispersion correction (D3 and D3(BJ)) are compared. PBE-D3, PBE-D3(BJ) and RPBE-D3 give similar results which exhibit a good agreement with experimental data. RevPBE-D3 and RevPBE-D3(BJ) tend to overestimate adsorption energies. The inclusion of three-center terms (PBE-D3(ABC)) leads to a slightly better agreement with the experiment in most cases. Vertical adsorbate–substrate distances are calculated and compared to previous theoretical results. The observed trends for the surfaces and metals are consistent with the calculated adsorption energies.

Experimental methods in chemical engineering: Density functional theory— DFT

2021 ◽  
Author(s):  
Hasan Al‐Mahayni ◽  
Xiao Wang ◽  
Jean‐Philippe Harvey ◽  
Gregory S. Patience ◽  
Ali Seifitokaldani
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Chemical Engineering ◽  
Experimental Methods ◽  
Functional Theory

A DFT study of spherands containing five anisyl groups — Highly preorganized to bind the alkali metal

2006 ◽  
Vol 84 (8) ◽  
pp. 1045-1049 ◽  
Author(s):  
Shabaan AK Elroby ◽  
Kyu Hwan Lee ◽  
Seung Joo Cho ◽  
Alan Hinchliffe
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Density Functional ◽  
Ionic Radius ◽  
Binding Energies ◽  
Cavity Size ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Good Agreement

Although anisyl units are basically poor ligands for metal ions, the rigid placements of their oxygens during synthesis rather than during complexation are undoubtedly responsible for the enhanced binding and selectivity of the spherand. We used standard B3LYP/6-31G** (5d) density functional theory (DFT) to investigate the complexation between spherands containing five anisyl groups, with CH2–O–CH2 (2) and CH2–S–CH2 (3) units in an 18-membered macrocyclic ring, and the cationic guests (Li+, Na+, and K+). Our geometric structure results for spherands 1, 2, and 3 are in good agreement with the previously reported X-ray diffraction data. The absolute values of the binding energy of all the spherands are inversely proportional to the ionic radius of the guests. The results, taken as a whole, show that replacement of one anisyl group by CH2–O–CH2 (2) and CH2–S–CH2 (3) makes the cavity bigger and less preorganized. In addition, both the binding and specificity decrease for small ions. The spherands 2 and 3 appear beautifully preorganized to bind all guests, so it is not surprising that their binding energies are close to the parent spherand 1. Interestingly, there is a clear linear relation between the radius of the cavity and the binding energy (R2 = 0.999).Key words: spherands, preorganization, density functional theory, binding energy, cavity size.

A theoretical study on solvatofluorochromic asymmetric thiazolothiazole (TTz) dyes using dielectric-dependent density functional theory

2021 ◽  
Vol 23 (37) ◽  
pp. 21078-21086
Author(s):  
Tomomi Shimazaki ◽  
Masanori Tachikawa
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Dye Molecules ◽  
Excitation Energies ◽  
Functional Theory ◽  
Dependent Density

In this work, the excitation energies of asymmetric thiazolothizaole (TTz) dye molecules have been theoretically studied using dielectric-dependent density functional theory (DFT).

scholarly journals STRUCTURAL AND ELECTRONIC PROPERTIES OF BRIDGED BITHIOPHENE S-OXIDES (BTO) WITH S, S=O, O, SiH2 and BH2 BRIDGE: SEMI-EMPIRICAL AND AB INITIO STUDY

2010 ◽  
Vol 18 (18) ◽  
pp. 1-10
Author(s):  
Banjo Semire ◽  
Isaiah Ajibade Adejoro ◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Study ◽  
Empirical Methods ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Semi Empirical ◽  
Good Agreement

In this paper, we theoretically studied the geometries, stabilities, electronic and thermodynamic properties of bridged bithiophene S-oxide (BTO-X) derivates (with X = BH2, SiH2, S, S=O, and O) by using semi-empirical methods, ab-initio, and Density functional theory. The geometries and thermodynamic parameters calculated by PM3 were in good agreement with that of B3LYP/6-31G(d). The bandgap calculated by B3LYP/6-31G(d) ranged from 3.94eV (BTO-O)-3.16eV (BTO-BH2). The absorption λmax calculated suing B3LYP/6-31G(d) shifted to longer wavelength with X=BH2, SiH2, and S=O due to enhancement of π-conjugated system whereas, BTO-S and BTO-O shifted to shorter wavelengths as compared to dimmer thiophene S-oxide (2TO).

A Theoretical Study of H2S Toxic Gas Adsorption on Pristine and Doped Monolayer (AlN)21 Using Density Functional Theory

2020 ◽  
Vol 12 (02) ◽  
pp. 99-111
Author(s):  
Jamal A. Shlaka ◽  
◽  
Abbas H. Abo Nasria
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Gas Adsorption ◽  
Aluminium Nitride ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Gas Molecules ◽  
Toxic Gas ◽  
Center Ring

Been studying the interactions between graphene - like aluminium nitride P(AlN)21 nano ribbons doped and defect (AlN)21Sheet, Molecules and small toxic gas molecules ( H2S), were built for two different adsorption sites on graphene like aluminium nitride P(AlN)21. this was done by employing B3LYP density functional theory (DFT) with 6-31G*(d,p) using Gaussian 09 program, Gaussian viw5.0 package of programs and Nanotube Modeller program 2018. the adsorptions of H2S on P(AlN)21, (C) atoms-doped P(AL-N)20 sheet, D-P(AL-N)20 and D-(C)atoms-doped P(AL-N)19 (on atom) with (Ead) (-0.468eV),(-0.473 eV), (-0.457 eV), (-0.4478 eV) and (-0.454 eV), respectively, (Ead) of H2S on the center ring of the P(AL-N)21, (C) atoms-doped P(AL-N)20 sheet, D-P(AL-N)20 and D-(C,B)atoms-doped P(AL-N)19 sheet are (-0.280 eV),(-0.465 eV), (-0.405 eV), (-0.468 eV) and -0.282 eV), respectively, are weak physisorption . However, the adsorptions of H2S, on the ((AlN)20 -B and D- (AlN)19 -B), (on atom N and center ring the sheet) are a strong chemisorption because of the (Ead) larger than -0.5 eV, due to the strong interaction, the ((AlN)20-B and D-(AlN)19-B), could catalyst or activate, through the results that we obtained, which are the improvement of the sheet P(AlN)21 by doping and per forming a defect in, it that can be used to design sensors. DOI: http://dx.doi.org/10.31257/2018/JKP/2020/120210

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