scholarly journals Graphene Support Effects on Palladium Catalyzed Reactions

2019 ◽  
Vol 20 (2) ◽  
Author(s):  
Kathleen Dreyer
Keyword(s):  
Binding Energy ◽  
Palladium Catalysts ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Catalytic Reactions ◽  
Graphene Interface ◽  
Palladium Catalyzed ◽  
Pd Clusters ◽  
Catalyzed Reactions

Palladium catalysts are often anchored to a support, such as graphitic carbon, to increase their overall surface area and facilitate catalytic reactions. There is a potential for interaction between the support and the catalyst, which can affect such reactions. At a certain palladium size threshold, it is hypothesized that the effects of the support on reactions on Pd are negligible. To determine this threshold, the Pd catalyst size and shape were varied (size was varied in the number of layers and number of Pd atoms, while shape ranged from hemispherical to spherical). The Pd clusters ranged from 2-5 layers and 38-293 atoms. Also, the graphene support was functionalized to different extents to test its effect on catalytic reactions on Pd. Initially, adsorption reactions of H*, O*, C*, OH*, and CH* onto supported Pd were tested to determine the effects of catalyst shape and size on the binding energy of such adsorbates. Periodic density functional theory calculations were used to determine these binding energies on bare Pd, Pd on a pure graphene support, and Pd on graphene functionalized with oxygen and hydroxide. These tests revealed that smaller Pd particles (about 100 atoms or fewer) are influenced by the support, showing large shifts in adsorbate binding energy from the pure graphene to the functionalized graphene. This shift in binding energy indicates that there are major changes in the catalytic behavior of sites upon which the adsorption reaction was tested, meaning that sites near the Pd-graphene interface might be affected by the support.

scholarly journals The investigation of 2D monolayers as potential chelation agents in Alzheimer’s disease

2019 ◽  
Author(s):  
Neha Pavuluru ◽  
Xuan Luo
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Charge Transfer ◽  
Binding Energy ◽  
Amyloid Beta ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Amyloid Beta Protein ◽  
Functional Theory

In this study, we conducted Density Functional Theory calculations comparing the binding energy of the copper- Amyloid-beta complex to the binding energies of potential chelation materials. We used the first-coordination sphere of the truncated high-pH Amyloid-beta protein subject to computational limits. Binding energy and charge transfer calculations were evaluated for copper’s interaction with potential chelators: monolayer boron nitride, monolayer molybdenum disulfide, and monolayer silicene. Silicene produced the highest binding energies to copper, and the evidence of charge transfer between copper and the monolayer proves that there is a strong ionic bond present. Although our three monolayers did not directly present chelation potential, the absolute differences between the binding energies of the silicene binding sites and the Amyloid-beta binding site were minimal proving that further research in silicene chelators may be useful for therapy in Alzheimer’s disease.

scholarly journals Antimony Selenide Crystals Encapsulated within Single Walled Carbon Nanotubes-A DFT Study

2009 ◽  
Vol 6 (s1) ◽  
pp. S147-S152 ◽  
Author(s):  
Navaratnarajah Kuganathan
Keyword(s):  
Carbon Nanotubes ◽  
Binding Energy ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Single Walled Carbon Nanotubes ◽  
Binding Energies ◽  
Single Walled Carbon ◽  
Transmission Electron ◽  
Antimony Selenide ◽  
Walled Carbon Nanotubes

The structure and binding energies of antimony selenide crystals encapsulated within single-walled carbon nanotubes are studied using density functional theory. Calculations were performed on the simulated Sb2Se3structure encapsulated within single walled nanotube to investigate the perturbations on the Sb2Se3crystal and tube structure and electronic structure and to estimate the binding energy. The calculated structures are in good agreement with the experimental high resolution transmission electron microscopy images of the Sb2Se3@SWNT. The calculated binding energy shows that larger diameter tube could accommodate the Sb2Se3crystals exothermically. Minimal charge transfer is observed between nanotube and the Sb2Se3crystals.

scholarly journals First-Principles Density Functional Theory Calculations of Bilayer Membranes Heterostructures of Ti3C2T2 (MXene)/Graphene and AgNPs

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 543
Author(s):  
Golibjon. R. Berdiyorov ◽  
Mohamed E. Madjet ◽  
Khaled. A. Mahmoud
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Structural Properties ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Silver Nanoclusters ◽  
Functional Theory ◽  
Bilayer Membranes ◽  
Principle Density Functional Theory

The properties of two-dimensional (2D) layered membrane systems can be medullated by the stacking arrangement and the heterostructure composition of the membrane. This largely affects the performance and stability of such membranes. Here, we have used first-principle density functional theory calculations to conduct a comparative study of two heterostructural bilayer systems of the 2D-MXene (Ti3C2T2, T = F, O, and OH) sheets with graphene and silver nanoparticles (AgNPs). For all considered surface terminations, the binding energy of the MXene/graphene and MXene/AgNPs bilayers increases as compared with graphene/graphene and MXene/MXene bilayer structures. Such strong interlayer interactions are due to profound variations of electrostatic potential across the layers. Larger interlayer binding energies in MXene/graphene systems were obtained even in the presence of water molecules, indicating enhanced stability of such a hybrid system against delamination. We also studied the structural properties of Ti3C2X2 MXene (X = F, O and OH) decorated with silver nanoclusters Agn (n ≤ 6). We found that regardless of surface functionalization, Ag nanoclusters were strongly adsorbed on the surface of MXene. In addition, Ag nanoparticles enhanced the binding energy between MXene layers. These findings can be useful in enhancing the structural properties of MXene membranes for water purification applications.

1,4,5,8-Tetraazafulvalene – Darstellung schwefelhaltiger Derivate und Zuordnung des Chromophors / 1,4,5,8-Tetraazafulvalenes – Synthesis of Sulfur-Containing Derivatives and Classification of the Chromophor

2004 ◽  
Vol 59 (4) ◽  
pp. 406-413 ◽  
Author(s):  
Christiane Kühn ◽  
R. Beckert ◽  
U.-W. Grummt ◽  
C. Käpplinger ◽  
E. Birckner
Keyword(s):  
Lipoic Acid ◽  
Density Functional ◽  
Tautomeric Form ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Different Types ◽  
Palladium Catalyzed ◽  
Catalyzed Reactions ◽  
Sulfur Containing

Abstract In order to obtain sulfur-containing tetraazafulvalenes the derivatives 1 - 3 were cross-coupled with different types of acetylenes via palladium-catalyzed reactions. Starting from the tetrabromoaryl derivative 3a, four bromine atoms could be replaced by 2-ethynylthiophene. Under analogous conditions, the methylsulfanyl esters 7 -11 could be obtained by employing 4-ethynylbenzoic acid 4-(methylsulfanyl)butylester 6. Lipoic acid could be integrated into tetraazafulvalenes successfully in a two step reaction. First, the Sonogashira coupling method yielded the compound 12 possessing two (4-anilino)ethynyl residues which were then condensed with lipoic acid to give derivative 13. Whereas the NMR data suggest the predominance of prototropic form A, UV/vis spectra of the deeply colored tetraazafulvalenes are in favor with structure B rather than with structure A. DFT calculations at the B3LYP/6-31G(d) level showed that tautomeric form B is about 60 kJ/mol more stable than A. In addition, time-dependent density functional theory calculations support the substructure of two crossed diazaheptamethinemerocyanines.

scholarly journals The investigation of 2D monolayers as potential chelation agents in Alzheimer’s disease

2019 ◽  
Author(s):  
Neha Pavuluru ◽  
Xuan Luo
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Charge Transfer ◽  
Binding Energy ◽  
Amyloid Beta ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Amyloid Beta Protein ◽  
Functional Theory

In this study, we conducted Density Functional Theory calculations comparing the binding energy of the copper- Amyloid-beta complex to the binding energies of potential chelation materials. We used the first-coordination sphere of the truncated high-pH Amyloid-beta protein subject to computational limits. Binding energy and charge transfer calculations were evaluated for copper’s interaction with potential chelators: monolayer boron nitride, monolayer molybdenum disulfide, and monolayer silicene. Silicene produced the highest binding energies to copper, and the evidence of charge transfer between copper and the monolayer proves that there is a strong ionic bond present. Although our three monolayers did not directly present chelation potential, the absolute differences between the binding energies of the silicene binding sites and the Amyloid-beta binding site were minimal proving that further research in silicene chelators may be useful for therapy in Alzheimer’s disease.

Density functional theory periodic slab calculations of adsorption and dissociation of H2O on the Cu2O(110):CuO surface

2013 ◽  
Vol 91 (12) ◽  
pp. 1101-1106 ◽  
Author(s):  
Sherin A. Saraireh ◽  
Mohammednoor Altarawneh
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Water Molecule ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Environmental Applications ◽  
Functional Theory ◽  
Adsorption And Dissociation

Interaction of water with Cu2O has many prominent industrial and environmental applications. This study represents detailed density-functional theory calculations investigating the adsorption of a water molecule on a Cu2O(110):CuO surface; one of the two most stable Cu2O surfaces under practical catalytic conditions of temperatures and pressures. We report herein structural geometries and binding energies for all plausible molecular and dissociative interaction of H2O with the surface. The water molecule is found to interact weakly with the Cu2O(110):CuO surface, forming several vertical and flat orientations where the latter was found to offer the most preferred site with a binding energy at 0.389 eV. Dissociation of a water molecule on this surface is found to incur a modest endothermcity of 0.71 eV.

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.

First-Principles Analysis on Interaction between Dopant (Ga, Sb) and Contamination Metal Atoms in Ge Crystals

2013 ◽  
Vol 205-206 ◽  
pp. 417-421
Author(s):  
Tatsunori Yamato ◽  
Koji Sueoka ◽  
Takahiro Maeta
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Functional Theory ◽  
Substitutional Site ◽  
Metal Impurities ◽  
Metal Atoms ◽  
Total Energies ◽  
Group 3

The lowest energetic configurations of metal impurities in 4throw (Sc - Zn), 5throw (Y - Cd) and 6throw (Hf - Hg) elements in Ge crystals were determined with density functional theory calculations. It was found that the substitutional site is the lowest energetic configuration for most of the calculated metals in Ge. The most stable configurations of dopant (Ga, Sb) - metal complexes in Ge crystals were also investigated. Following results were obtained. (1) For Ga dopant, 1st neighbor T-site is the most stable for metals in group 3 to 7 elements while substitutional site next to Ga atom is the most stable for metals in group 8 to 12 elements. (2) For Sb dopant, substitutional site next to Sb atom is the most stable for all calculated metals. Binding energies of the interstitial metalMiwith the substitutional dopantDswere obtained by the calculated total energies. The calculated results for Ge were compared with those for Si.

scholarly journals Including dispersion interactions in the ONETEP program for linear-scaling density functional theory calculations

2008 ◽  
Vol 465 (2103) ◽  
pp. 669-683 ◽  
Author(s):  
Quintin Hill ◽  
Chris-Kriton Skylaris
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Cost ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Molecular Structures ◽  
Dispersion Interactions ◽  
Biomolecular Systems ◽  
Functional Theory ◽  
High Level

While density functional theory (DFT) allows accurate quantum mechanical simulations from first principles in molecules and solids, commonly used exchange-correlation density functionals provide a very incomplete description of dispersion interactions. One way to include such interactions is to augment the DFT energy expression by damped London energy expressions. Several variants of this have been developed for this task, which we discuss and compare in this paper. We have implemented these schemes in the ONETEP program, which is capable of DFT calculations with computational cost that increases linearly with the number of atoms. We have optimized all the parameters involved in our implementation of the dispersion correction, with the aim of simulating biomolecular systems. Our tests show that in cases where dispersion interactions are important this approach produces binding energies and molecular structures of a quality comparable with high-level wavefunction-based approaches.

Diffusion of Fluorine-Silicon Interstitial Complex in Crystalline Silicon

2005 ◽  
Vol 864 ◽  
Author(s):  
Scott A. Harrison ◽  
Thomas F. Edgar ◽  
Gyeong S. Hwang
Keyword(s):  
Density Functional Theory ◽  
Binding Energy ◽  
Charge State ◽  
First Principles ◽  
Density Functional ◽  
Positive Charge ◽  
Crystalline Silicon ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
And Diffusion

AbstractBased on first principles density functional theory calculations, we identify the structure and diffusion pathway for a fluorine-silicon interstitial complex (F-Sii). We find the F-Sii complex to be most stable in the singly positive charge state at all Fermi leVels. At mid-gap, the complex is found to have a binding energy of 1.08 eV relative to bond-centered F+ and (110)-split Sii. We find the F-Sii complex has an overall migration barrier of 0.76 eV, which suggests that this complex may play an important role in fluorine diffusion. Our results should lead to more accurate models that describe the behavior of fluorine co-implants crystalline silicon.

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