scholarly journals Electrochemical Deposition of Copper on Epitaxial Graphene

2020 ◽  
Vol 10 (4) ◽  
pp. 1405 ◽  
Author(s):  
Ivan Shtepliuk ◽  
Mikhail Vagin ◽  
Rositsa Yakimova
Keyword(s):  
Density Functional ◽  
Epitaxial Graphene ◽  
Computational Techniques ◽  
Copper Electrodeposition ◽  
Metal Contacts ◽  
Kinetic Measurements ◽  
Nucleation Sites ◽  
Starting Point ◽  
Instantaneous Nucleation ◽  
Nucleation Mechanisms

Understanding the mechanism of metal electrodeposition on graphene as the simplest building block of all graphitic materials is important for electrocatalysis and the creation of metal contacts in electronics. The present work investigates copper electrodeposition onto epitaxial graphene on 4H-SiC by experimental and computational techniques. The two subsequent single-electron transfer steps were coherently quantified by electrochemistry and density functional theory (DFT). The kinetic measurements revealed the instantaneous nucleation mechanism of copper (Cu) electrodeposition, controlled by the convergent diffusion of reactant to the limited number of nucleation sites. Cu can freely migrate across the electrode surface. These findings provide fundamental insights into the nature of copper reduction and nucleation mechanisms and can be used as a starting point for performing more sophisticated investigations and developing real applications.

A Rare Low Spin Co(IV) Bis-Silyldiamide with High Thermal Stability: Exploring the Origin of an Unusual S = 1/2 Configuration

2020 ◽  
Author(s):  
David Zanders ◽  
Goran Bačić ◽  
Dominique Leckie ◽  
Oluwadamilola Odegbesan ◽  
Jeremy M. Rawson ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Density Functional ◽  
Atomic Layer ◽  
Epr Spectrum ◽  
Functional Theory ◽  
Cluster Calculations ◽  
Layer Deposition ◽  
Starting Point ◽  
Higher Spin ◽  
Surface Saturation

Attempted preparation of a chelated Co(II) β-silylamide re-sulted in the unprecedented disproportionation to Co(0) and a spirocyclic cobalt(IV) bis(β-silyldiamide): [Co[(NtBu)2SiMe2]2] (1). Compound 1 exhibits a room temperature magnetic moment of 1.8 B.M and a solid state axial EPR spectrum diagnostic of a rare S = 1/2 configuration. Semicanonical coupled-cluster calculations (DLPNO-CCSD(T)) revealed the doublet state was clearly preferred (–27 kcal/mol) over higher spin configurations for which density functional theory (DFT) showed no energetic preference. Unlike other Co(IV) complexes, 1 had remarkable thermal stability, and was demonstrated to form a stable self-limiting monolayer in initial atomic layer deposition (ALD) surface saturation tests. The ease of synthesis and high-stability make 1 an attractive starting point to begin investigating otherwise inaccessible Co(IV) intermediates and synthesizing new materials.

scholarly journals Direct Kinetic Measurements and Master Equation Modelling of the Unimolecular Decomposition of Resonantly-Stabilized CH2CHCHC(O)OCH3 Radical and an Upper Limit Determination for CH2CHCHC(O)OCH3 + O2 Reaction

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1251-1268 ◽  
Author(s):  
Satya Prakash Joshi ◽  
Prasenjit Seal ◽  
Timo Theodor Pekkanen ◽  
Raimo Sakari Timonen ◽  
Arrke J. Eskola
Keyword(s):  
Master Equation ◽  
Density Functional ◽  
Rate Coefficient ◽  
Decomposition Kinetics ◽  
Basis Sets ◽  
Stationary Points ◽  
Unimolecular Decomposition ◽  
Kinetic Measurements ◽  
Point Energy ◽  
Upper Limit

AbstractMethyl-Crotonate (MC, (E)-methylbut-2-enoate, CH3CHCHC(O)OCH3) is a potential component of surrogate fuels that aim to emulate the combustion of fatty acid methyl ester (FAME) biodiesels with significant unsaturated FAME content. MC has three allylic hydrogens that can be readily abstracted under autoignition and combustion conditions to form a resonantly-stabilized CH2CHCHC(O)OCH3 radical. In this study we have utilized photoionization mass spectrometry to investigate the O2 addition kinetics and thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical. First we determined an upper limit for the bimolecular rate coefficient of CH2CHCHC(O)OCH3 + O2 reaction at 600 K (k ≤ 7.5 × 10−17 cm3 molecule−1 s−1). Such a small rate coefficient suggest this reaction is unlikely to be important under combustion conditions and subsequent efforts were directed towards measuring thermal unimolecular decomposition kinetics of CH2CHCHC(O)OCH3 radical. These measurements were performed between 750 and 869 K temperatures at low pressures (<9 Torr) using both helium and nitrogen bath gases. The potential energy surface of the unimolecular decomposition reaction was probed at density functional (MN15/cc-pVTZ) level of theory and the electronic energies of the stationary points obtained were then refined using the DLPNO-CCSD(T) method with the cc-pVTZ and cc-pVQZ basis sets. Master equation simulations were subsequently carried out using MESMER code along the kinetically important reaction pathway. The master equation model was first optimized by fitting the zero-point energy corrected reaction barriers and the collisional energy transfer parameters $\Delta{E_{{\text{down}},\;{\text{ref}}}}$ and n to the measured rate coefficients data and then utilize the constrained model to extrapolate the decomposition kinetics to higher pressures and temperatures. Both the experimental results and the MESMER simulations show that the current experiments for the thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical are in the fall-off region. The experiments did not provide definite evidence about the primary decomposition products.

Theoretical determination of the structures of CaSiO3 perovskites

2006 ◽  
Vol 62 (6) ◽  
pp. 1025-1030 ◽  
Author(s):  
Razvan Caracas ◽  
Renata M. Wentzcovitch
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Determination ◽  
Functional Theory ◽  
Starting Point ◽  
Atomic Coordinates ◽  
The Ideal

Density functional theory is used to determine the possible crystal structure of the CaSiO3 perovskites and their evolution under pressure. The ideal cubic perovskite is considered as a starting point for studying several possible lower-symmetry distorted structures. The theoretical lattice parameters and the atomic coordinates for all the structures are determined, and the results are discussed with respect to experimental data.

Physical Based Microstructure Modelling Coupled with Nucleation Theory during and after Hot Forming of AA5083

2010 ◽  
Vol 89-91 ◽  
pp. 509-514
Author(s):  
Pavel Sherstnev ◽  
Christof Sommitsch ◽  
Stefan Mitsche ◽  
Carsten Melzer
Keyword(s):  
Aluminium Alloy ◽  
Hot Rolling ◽  
Volume Fraction ◽  
Electron Backscatter Diffraction ◽  
Grain Structure ◽  
Nucleation Theory ◽  
Structure Evolution ◽  
Nucleation Sites ◽  
Nucleation Mechanisms ◽  
Backscatter Diffraction

A physical model based on three types of dislocations and three nucleation sites for recrystallized grain is applied to hot rolling simulation. This model was implemented into a commercial Finite Element (FE) analysis package FORGE 2008 to calculate both the structure evolution during and the recrystallized volume fraction after hot working of aluminium alloy 5083. It is shown that the main nucleation mechanisms in the aluminium alloy are the particle stimulated nucleation (PSN) and nucleation at grain boundaries. Hence the precipitation kinetics during homogenisation was investigated by use of the thermodynamic calculation software MatCalc. To validate the simulation results hot rolling experiments were performed by means of a laboratory mill. The grain structure evolution was analysed by electron backscatter diffraction (EBSD).

High-yield synthesis of CsPbBr3 nanoparticles: Diphenylphosphine as a reducing agent and its effect in Pb-seeding nucleation and growth

2021 ◽  
Author(s):  
Eder Antonio Castillo-Ruiz ◽  
Diana Fabiola Garcia-Gutierrez ◽  
Domingo Ixcóatl Garcia-Gutierrez
Keyword(s):  
Nucleation And Growth ◽  
Reducing Agent ◽  
High Yield ◽  
Reaction Yield ◽  
High Quality ◽  
Stabilizing Agents ◽  
Nucleation Sites ◽  
Nucleation Mechanisms ◽  
Attractive Option ◽  
Mass Increment

Abstract Based on the reported nucleation mechanisms for CsPbX3 and II-VI/IV-VI quantum dots, CsPbBr3 nanoparticles with a high reaction-yield, up to 393% mass-increment, were synthesized by the hot-injection method. The introduction of diphenylphosphine (DPP) as a reducing agent improved nanoparticle nucleation and growth, giving out evidence for Pb-seeding in CsPbBr3 nanoparticles formation. Additionally, a clear influence of the DPP in a CsPbBr3-Cs4PbBr6 incomplete phase transformation was observed, marked by the appearance of several PbBr2 nanoparticles, indicating the need for an improved ratio between the stabilizing agents and the precursors, due to the increased number of nucleation sites produced by the DPP. The resulting CsPbBr3 nanoparticles showed high quality, as they displayed 70%-90% photoluminescence quantum yield (PLQY), narrow size distribution with an average nanoparticle size of ~10 nm and the characteristic cubic morphology reported in previous works. This increment in CsPbBr3 nanoparticles’ reaction yield will contribute to making them a more attractive option for different optoelectronic applications.

Photoresponse in epitaxial graphene with asymmetric metal contacts

2012 ◽  
Vol 100 (9) ◽  
pp. 093116 ◽  
Author(s):  
Ram Sevak Singh ◽  
Venkatram Nalla ◽  
Wei Chen ◽  
Wei Ji ◽  
Andrew T. S. Wee
Keyword(s):  
Epitaxial Graphene ◽  
Metal Contacts

scholarly journals Study of interaction energies between residues of the active site of Hsp90 and geldanamycin analogues using quantum mechanics/molecular mechanics methods

F1000Research ◽  
2019 ◽  
Vol 8 ◽  
pp. 2040
Author(s):  
Ricardo Vivas-Reyes ◽  
Alejando Morales-Bayuelo ◽  
Carlos Gueto ◽  
Juan C. Drosos ◽  
Johana Márquez Lázaro ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Biological Activity ◽  
Active Site ◽  
Density Functional ◽  
Biological Response ◽  
Computational Techniques ◽  
Quantum Similarity ◽  
Interaction Energies ◽  
Atp Binding Site ◽  
Hsp90 Chaperone

Background: Heat shock protein (Hsp90KDa) is a molecular chaperone involved in the process of cellular oncogenesis, hence its importance as a therapeutic target in clinical trials. Geldanamycin is an inhibitor of Hsp90 chaperone activity, which binds to the ATP binding site in the N-terminal domain of Hsp90. However, geldanamycin has shown hepatotoxic damage in clinical trials; for this reason, its use is not recommended. Taking advantage that geldanamycin binds successfully to Hsp90, many efforts have focused on the search for similar analogues, which have the same or better biological response and reduce the side effects of its predecessor; 17-AAG and 17-DMAG are examples of these analogues. Methods: In order to know the chemical factors influencing the growth or decay of the biological activity of geldanamycin analogues, different computational techniques such as docking, 3DQSAR and quantum similarity were used.  Moreover, the study quantified the interaction energy between amino acids residues of active side and geldanamycin analogues, through hybrid methodologies and density functional theory (DFT) indexes. Results: The evaluation of interaction energies showed that the interaction with Lys58 residue is essential for the union of the analogues to the active site of Hsp90, and improves its biological activity. This union is formed through a substituent on C-11 of the geldanamycin macrocycle. A small and attractor group was found as the main steric and electrostatic characteristic that substituents on C11 need in order to interact with Lys 58; behavior was observed with hydroxy and methoxy series of geldanamycin analogues, under study. Conclusion: These outcomes were supported with quantum similarity and reactivity indices calculations using DFT in order to understand the non-covalent stabilization in the active site of these compounds.

scholarly journals Controlling Thermal Stability and Volatility of Organogold(I) Compounds for Vapor Deposition with Complementary Ligand Design

2019 ◽  
Author(s):  
Matthew Griffiths ◽  
Zachary Dubrawski ◽  
Goran Bačić ◽  
Jason Masuda ◽  
Achini Japahuge ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Vapor Deposition ◽  
Figure Of Merit ◽  
Density Functional ◽  
Computational Techniques ◽  
Functional Theory ◽  
Design Studies ◽  
X Ray Crystallography ◽  
Compare And Contrast ◽  
Thermal Stability Of

We compare and contrast the volatility and thermal stability of a family of twelve organometallic gold(I) compounds using a combination of X-ray crystallography, thermogravimetric analysis (TGA), and density functional theory (DFT) techniques. Pentafluorophenyl is used as a new ligand for vapor deposition which produces rather low volatility, but very thermally stable compounds when combined with PMe<sub>3</sub> and <i>N</i>,<i>N</i>'-di-<i>tert</i>-butylimidazolidin-2-ylidene. We introduce a precursor figure of merit that can be used to rank precursor usefulness. Using DFT, we find a linear correlation between Au-L bond strength and thermal stability, which demonstrates the power of computational techniques to predict successful synthetic targets for future precursor design studies.

scholarly journals Controlling Thermal Stability and Volatility of Organogold(I) Compounds for Vapor Deposition with Complementary Ligand Design

2019 ◽  
Author(s):  
Matthew Griffiths ◽  
Zachary Dubrawski ◽  
Goran Bačić ◽  
Jason Masuda ◽  
Achini Japahuge ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Vapor Deposition ◽  
Figure Of Merit ◽  
Density Functional ◽  
Computational Techniques ◽  
Functional Theory ◽  
Design Studies ◽  
X Ray Crystallography ◽  
Compare And Contrast ◽  
Thermal Stability Of

We compare and contrast the volatility and thermal stability of a family of twelve organometallic gold(I) compounds using a combination of X-ray crystallography, thermogravimetric analysis (TGA), and density functional theory (DFT) techniques. Pentafluorophenyl is used as a new ligand for vapor deposition which produces rather low volatility, but very thermally stable compounds when combined with PMe<sub>3</sub> and <i>N</i>,<i>N</i>'-di-<i>tert</i>-butylimidazolidin-2-ylidene. We introduce a precursor figure of merit that can be used to rank precursor usefulness. Using DFT, we find a linear correlation between Au-L bond strength and thermal stability, which demonstrates the power of computational techniques to predict successful synthetic targets for future precursor design studies.

scholarly journals Preparation, thermal stability and electrical transport properties of vaesite, NiS2

2019 ◽  
Author(s):  
Helena M Ferreira ◽  
Elsa B Lopes ◽  
José F Malta ◽  
Luís M Ferreira ◽  
Maria H Casimiro ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Electrical Transport ◽  
Hot Pressing ◽  
Density Functional ◽  
Single Phase ◽  
Electronic Band Structure ◽  
Electrical Transport Properties ◽  
Electronic Band ◽  
Metallic Behavior ◽  
Starting Point

Vaesite, a nickel chalcogenide with NiS2 formula, has been synthetized and studied by theoretical and experimental methods. NiS2 was prepared by solid-state reaction under vacuum and densified by hot-pressing, at different consolidation conditions. Dense single-phase pellets (relative densities >94%) were obtained, without significant lattice distortions for different hot-pressing conditions. The thermal stability of NiS2 was studied by thermogravimetric analysis. Both as-synthetized and hot-pressed NiS2 have a single phase nature, although some hot-pressed samples had traces of the sulfur deficient phase, Ni1-xS (<1%vol), due to the strong desulfurization at T > 340ºC. The electronic band structure and density of states were calculated by Density Functional Theory (DFT), indicating a metallic behavior. However, the electronic transport measurements showed p-type semiconductivity for bulk NiS2, verifying its characteristic behavior has a Mott insulator. The consolidation conditions strongly influence the electronic properties, with the best room-temperature Seebeck coefficient, electrical resistivity and power factor being 182µVK-1, 2257μΩm and 14.1µWK-2m-1, respectively, pointing this compound as a good starting point for a new family of thermoelectric materials.

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