Aluminum adsorption on graphene: Theoretical study of dispersion effects

2019 ◽  
Vol 18 (04) ◽  
pp. 1950019
Author(s):  
Ana C. Rossi Fernández ◽  
Nicolás F. Domancich ◽  
Ricardo M. Ferullo ◽  
Norberto J. Castellani
Keyword(s):  
Density Functional ◽  
Single Atom ◽  
Ionic Character ◽  
Dispersion Interactions ◽  
Functional Theory ◽  
Dispersion Effects ◽  
Adsorption Mode ◽  
The Density Functional Theory ◽  
Analysis Of Results ◽  
Dispersion Character

The interaction between a single atom and graphene is an example in which the density functional theory (DFT) presents serious difficulties in giving an appropriate description of the adsorbate–substrate interaction, giving also different predictions according to the chosen approximation. The present calculations sustain that the inclusion of dispersion interactions in the framework of DFT for the Al/graphene system lead to potential energy curves of different nature according to the theoretical approach employed. The adsorption of an Al atom on the graphene surface was studied using both cluster and slab models. Cluster DFT–PBE calculations show the presence of a minimum at hollow site at an Al–graphene distance of about 2.1–2.3 Å corresponding to an exothermic state. Conversely, under B3LYP the same adsorption mode is endothermic. In comparison, our MP2 reference calculations predict the formation of two minima, both of exothermic nature, separated by an important energy barrier (about 0.2–0.4[Formula: see text]eV). The incorporation of empirical van der Walls (vdW) corrections to B3LYP changes the original behavior, giving an exothermic adsorption; furthermore, it produces a second, more external minimum. Slab calculations with PBE, and specially using the vdW-DF2 functional, predict also the formation of a minimum of very low depth at about 3.1 Å. The analysis of results obtained with cluster and slab models sustains that the bonding of the inner minima is of ionic character while that of the external ones is of dispersion character.

Single-atom Pt on non-metal modified graphene sheets as efficient catalysts for CO oxidation

2019 ◽  
Vol 43 (24) ◽  
pp. 9555-9565 ◽  
Author(s):  
Yanan Tang ◽  
Haiquan Zhang ◽  
Jincheng Zhou ◽  
Weiguang Chen ◽  
Huadou Chai ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Electronic Structures ◽  
Density Functional ◽  
Catalytic Properties ◽  
Single Atom ◽  
Graphene Sheets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Modified Graphene

By the density functional theory (DFT) calculations, the formation geometries, electronic structures and catalytic properties of metal Pt and nonmetal (NM) atom-co-modified graphene (Pt–3NM–graphene, NM = N, Si, P) as reactive substrates were investigated.

scholarly journals Computational Insights on the Mechanism of the Chemiluminescence Reaction of New Group of Chemiluminogens—10-Methyl-9-thiophenoxycarbonylacridinium Cations

2020 ◽  
Vol 21 (12) ◽  
pp. 4417
Author(s):  
Milena Pieńkos ◽  
Beata Zadykowicz
Keyword(s):  
Quantum Yield ◽  
Density Functional ◽  
Single Atom ◽  
Human Organism ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Aqueous Environments ◽  
Td Dft ◽  
Electronically Excited ◽  
Potential Applicability

Immunodiagnostics, in which one of the promising procedures is the chemiluminescent labelling, is essential to facilitate the detection of infections in a human organism. One of the standards commonly used in luminometric assays is luminol, which characterized by low quantum yield in aqueous environments. Acridinium esters have better characteristics in this topic. Therefore, the search for new derivatives, especially those characterized by the higher quantum yield of chemiluminescence, is one of the aims of the research undertaken. Using the proposed mechanism of chemiluminescence, we examined the effect of replacing a single atom within a center of reaction on the efficient transformation of substrates into electronically excited products. The density functional theory (DFT) and time dependent (TD) DFT calculated thermodynamic and kinetic data concerning the chemiluminescence and competitive dark pathways suggests that some of the scrutinized derivatives have better characteristics than the chemiluminogens used so far. Synthesis of these candidates for efficient chemiluminogens, followed by studies of their chemiluminescent properties, and ultimately in chemiluminescent labelling, are further steps to confirm their potential applicability in immunodiagnostics.

scholarly journals Single-Atom X/g-C3N4(X = Au1, Pd1, and Ru1) Catalysts for Acetylene Hydrochlorination: A Density Functional Theory Study

Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 808 ◽  
Author(s):  
Zhou ◽  
Zhu ◽  
Kang
Keyword(s):  
Density Functional Theory ◽  
Energy Barrier ◽  
Density Functional ◽  
Single Atom ◽  
Functional Theory ◽  
Acetylene Hydrochlorination ◽  
B3lyp Method ◽  
The Density Functional Theory ◽  
Catalytic Mechanisms ◽  
Functional Dispersion

The mechanisms of the single-atom X/g-C3N4(X = Au1, Pd1, and Ru1) catalysts for the acetylene hydrochlorination reaction were systematically investigated using the density functional theory (DFT) B3LYP method. The density functional dispersion correction obtained by the DFT-D3 method was taken into account. During the reaction, C2H2 and HCl were well activated and the analysis of the adsorption energy demonstrated the adsorption performance of C2H2 is better than that of HCl. The catalytic mechanisms of the three catalysts consist of one intermediate and two transition states. Moreover, our results showed that the three single-atom catalysts improve the catalytic activity of the reaction to different degrees. The calculated energy barrier declines in the order of Pd1/g-C3N4 > Ru1/g-C3N4 > Au1/g-C3N4, and the energy barrier for the Au1/g-C3N4 catalyst was only 13.66 kcal/mol, proving that single-atom Au1/g-C3N4 may be a potential catalyst for hydrochlorination of acetylene to vinyl chloride.

Ab-initio Studies of the Electronic Structures of the Hexavalent Uranium Compounds K2UO4 and Na4UO5

2014 ◽  
Vol 69 (1) ◽  
pp. 109-115
Author(s):  
Samir F. Matar
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Ionic Character ◽  
Functional Theory ◽  
Hexavalent Uranium ◽  
Conduction Bands ◽  
Uranium Compounds ◽  
The Density Functional Theory ◽  
Volume Equations ◽  
Theoretical Results

Band theoretical results within the density functional theory are reported for the uranates K2UO4 and Na4UO5. The two structures are differentiated respectively by uranyl and reverse uranyl-type short U-O distances characterizing the UO6 octahedra, as also reflected by larger compressibility and stability of the potassium-based uranate derived from energy-volume equations of states and the cohesive energy. A larger ionic character of Na4UO5 is inferred from comparative Bader charge analyses. The two uranates are insulators with a larger band gap and less extended valence and conduction bands for Na4UO5. Chemical bonding shows major interactions for U-O versus Na,K-O and is further differentiated as a function of the distances. The band structure results confirm the hexavalent character of the uranium atoms.

A strategy for enhancing the photoactivity of g-C3N4-based single-atom catalysts via sulphur doping: a theoretical study

2021 ◽  
Vol 23 (11) ◽  
pp. 6632-6640
Author(s):  
Yanqing Guo ◽  
Meng Xia ◽  
Mingkun Zhang ◽  
Jing Zou ◽  
Yue You ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Photocatalytic Activity ◽  
Density Functional ◽  
Carbon Nitride ◽  
Theoretical Study ◽  
Density Functional Theory Calculations ◽  
Graphitic Carbon Nitride ◽  
Single Atom ◽  
Functional Theory ◽  
The Density Functional Theory

The sulphur-doping strategy was proposed to enhance the incorporation of single Pt atoms in monolayer graphitic carbon nitride and the density functional theory calculations verified it has superb photocatalytic activity.

scholarly journals BNPd single-atom catalysts for selective hydrogenation of acetylene to ethylene: a density functional theory study

2018 ◽  
Vol 5 (7) ◽  
pp. 171598 ◽  
Author(s):  
Wanqi Gong ◽  
Lihua Kang
Keyword(s):  
Density Functional Theory ◽  
Selective Hydrogenation ◽  
Density Functional ◽  
Hydrogenation Reaction ◽  
Basis Set ◽  
Single Atom ◽  
Dissociative Chemisorption ◽  
Functional Theory ◽  
Selective Hydrogenation Of Acetylene ◽  
The Density Functional Theory

The mechanisms of selective hydrogenation of acetylene to ethylene on B 11 N 12 Pd single-atom catalyst were investigated through the density functional theory by using the 6-31++G** basis set. We studied the adsorption characteristics of H 2 and C 2 H 2 , and simulated the reaction mechanism. We discovered that H 2 underwent absolute dissociative chemisorption on single-atom Pd, forming the B 11 N 12 Pd(2H) dihydride complex, and then the hydrogenation reaction with C 2 H 2 proceeded. The hydrogenation reaction of acetylene on the B 11 N 12 Pd complex complies with the Horiuti–Polanyi mechanism, and the energy barrier was as low as 26.55 kcal mol −1 . Meanwhile, it also has a higher selectivity than many bimetallic alloy single-atom catalysts.

Charge-density distribution in hydrogen methylphosphonates of calcium and lithium

2011 ◽  
Vol 67 (5) ◽  
pp. 399-408 ◽  
Author(s):  
Adrian Mermer ◽  
Przemysław Starynowicz
Keyword(s):  
Density Functional ◽  
Metal Cations ◽  
Ionic Character ◽  
Topological Properties ◽  
Charge Density Distribution ◽  
Functional Theory ◽  
X Ray ◽  
Charge Densities ◽  
The Density Functional Theory ◽  
Calcium Compound

Two new crystal structures, calcium bis(hydrogen methylphosphonate), Ca(CH3PO3H)2, and lithium hydrogen methylphosphonate, Li(CH3PO3H), have been obtained, and the experimental and theoretical charge densities, as well as their topological properties, are reported. Both compounds display layered structures. Each hydrogen methylphosphonate anion coordinates three metal cations in the calcium compound and four in the lithium one. Weak polarization of oxygen lone pairs is observed, with lithium showing somewhat stronger polarization strength than calcium. The reported topological properties from the density functional theory (DFT) and X-ray approach are consistent with each other. In both structures the P—O bonds have a significant share of ionic character. The hyperconjugation effects within the phosphonate group are quenched upon coordination of the metal cations.

scholarly journals Strain Investigation on Spin-Dependent Transport Properties of γ-Graphyne Nanoribbon Between Gold Electrodes

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yun Li ◽  
Xiaobo Li ◽  
Shidong Zhang ◽  
Liemao Cao ◽  
Fangping Ouyang ◽  
...  
Keyword(s):  
Transport Properties ◽  
High Performance ◽  
Density Functional ◽  
Strain Engineering ◽  
Molecular Junctions ◽  
Spin Splitting ◽  
Functional Theory ◽  
Spin Dependent Transport ◽  
The Density Functional Theory ◽  
Dependent Transport

AbstractStrain engineering has become one of the effective methods to tune the electronic structures of materials, which can be introduced into the molecular junction to induce some unique physical effects. The various γ-graphyne nanoribbons (γ-GYNRs) embedded between gold (Au) electrodes with strain controlling have been designed, involving the calculation of the spin-dependent transport properties by employing the density functional theory. Our calculated results exhibit that the presence of strain has a great effect on transport properties of molecular junctions, which can obviously enhance the coupling between the γ-GYNR and Au electrodes. We find that the current flowing through the strained nanojunction is larger than that of the unstrained one. What is more, the length and strained shape of the γ-GYNR serves as the important factors which affect the transport properties of molecular junctions. Simultaneously, the phenomenon of spin-splitting occurs after introducing strain into nanojunction, implying that strain engineering may be a new means to regulate the electron spin. Our work can provide theoretical basis for designing of high performance graphyne-based devices in the future.

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