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Статті в журналах з теми "Kinetic modelling, density functional theory (DFT)"

1

Sibanda, David, Sunday Temitope Oyinbo, and Tien-Chien Jen. "A review of atomic layer deposition modelling and simulation methodologies: Density functional theory and molecular dynamics." Nanotechnology Reviews 11, no. 1 (January 1, 2022): 1332–63. http://dx.doi.org/10.1515/ntrev-2022-0084.

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Abstract The use of computational modelling and simulation methodologies has grown in recent years as researchers try to understand the atomic layer deposition (ALD) process and create new microstructures and nanostructures. This review article explains and simplifies two simulation methodologies, molecular dynamics and the density functional theory (DFT), in solving atomic layer deposition problems computationally. We believe that these simulation methodologies are powerful tools that can be utilised in atomic layer deposition. DFT is used to solve problems in surface science and catalysis (predicting surface energy, adsorption energy, charge transfer, etc.), semiconductors (band structure, defect bands, band gap, etc.), superconductors (electron–phonon coupling, critical transition temperature), and molecular electronics (conductance, current–voltage characteristics). Molecular dynamics (MD) is used to predict the kinetic and thermodynamic properties of a material. Of interest in this article is a review where different material problems emanating from atomic layer deposition from these fields have been addressed by DFT and MD. Selected publications are discussed where DFT and MD have been successfully applied in atomic layer deposition (and related processes in some instances). The applications of DFT stretch from binding energy calculations of molecules and the solid band structure in chemistry and physics, respectively, computing the electron density up to determining the properties of a many-electron system. Also highlighted in this review study are the challenges that DFT and MD simulations must overcome.
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2

Žula, Matej, Miha Grilc, Andrii Kostyniuk, Giorgio Tofani, Edita Jasiukaitytė-Grojzdek, Tina Ročnik Kozmelj, Ramesh Kumar Chowdari, et al. "Biorefining Twin Transition: Digitalisation for Bio-based Chemicals/Materials - Discovery, Design and Optimisation." CHIMIA 77, no. 12 (December 20, 2023): 816–26. http://dx.doi.org/10.2533/chimia.2023.816.

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The article discusses the production of platform chemicals from various biological sources, including glycerol, lignin, cellulose, bio-oils, and sea products. It presents the results of catalytic and downstream processes involved in the conversion of these biomass-derived feedstocks. The experimental approaches are complemented by numerical descriptions, ranging from density functional theory (DFT) calculations to kinetic modellingof the experimental data. This multi-scale modelling approach helps to understand the underlying mechanisms and optimize the production of platform chemicals from renewable resources.
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Taifan, William, Adam A. Arvidsson, Eric Nelson, Anders Hellman, and Jonas Baltrusaitis. "CH4 and H2S reforming to CH3SH and H2 catalyzed by metal-promoted Mo6S8 clusters: a first-principles micro-kinetic study." Catalysis Science & Technology 7, no. 16 (2017): 3546–54. http://dx.doi.org/10.1039/c7cy00857k.

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Density Functional Theory (DFT) and microkinetic modelling of CH4 and H2S reactions to form CH3SH and H2 as a first step in elucidating complex pathways in oxygen-free sour gas reforming was performed.
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Krayovskyy, Volodymyr, Volodymyr Pashkevych, Andriy Horpenuk, Volodymyr Romaka, Yuriy Stadnyk, Lyubov Romaka, Andriy Horyn, and Vitaliy Romaka. "RESEARCH OF THERMOMETRIC MATERIAL Er1-xScxNiSb. I. MODELLING OF PERFORMANCES." Measuring Equipment and Metrology 82, no. 2 (2021): 16–21. http://dx.doi.org/10.23939/istcmtm2021.02.016.

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Automated The results of modeling performances of the semiconductor solid solution Er1-xScxNiSb are presented, which can be a promising thermometric material for the manufacture of sensitive elements of thermoelectric and electroresistive thermocouples. Fullprof Suite software was used to model the crystallographic characteristics of the Er1-xScxNiSb thermometric material. Modeling of the electronic structure of Er1-xScxNiSb was performed by Coring-Kon-Rostocker methods in the approximation of coherent potential and local density using the exchange-correlation potential Moruzzi-Janak-Williams and Linear Muffin-Tin Orbital in the framework of DFT density functional theory. The Brillouin zone was divided into 1000 k-points, which were used to model energetic performances by calculating DOS. The width of the energy window was 22 eV and was chosen to capture all semi-core states of p-elements. Full potential (FP) was used in the representation of the linear MT orbital in the representation of plane waves. The accuracy of calculating the position of the Fermi level was εF ± 6 meV. To verify the existence of a continuous solid solution, Er1-xScxNiSb substitution, the change in the values of the period of the unit cell a (x) was calculated within the framework of the DFT density functional theory in the range x = 0–1.0. It is presented that the calculated and experimentally obtained dependences of the period of the unit cell a(x) Er1-xScxNiSb are almost parallel, which confirms the correctness of the used tools and the obtained modeling results. To research the possibility of obtaining thermometric material Er1-xScxNiSb in the form of a continuous solid solution was performed modeling of thermodynamic calculations in the approximation of harmonic oscillations of atoms in the theory of DFT density functional for a hypothetical solid solution Er1-xScxNiSb, x = 0–1.0. It is shown that the change in the values of free energy ΔG(x) (Helmholtz potential) passes through the minimum at the concentration x≈0.1 for all temperatures of possible homogenizing annealing of the samples, indicating the solubility limit of Sc atoms in the structure of the ErNiSb compound. The presence of this minimum indicates that the substitution of Er atoms for Sc atoms in the ErNiSb compound is energetically advantageous only up to the concentration of impurity atoms Sc, x≈0.1. At higher concentrations of Sc atoms, x> 0.10, stratification occurs (spinoidal phase decay). It is shown that modeling of the mixing entropy behavior S even at a hypothetical temperature T = 4000 K shows the absence of complete solubility of Sc atoms in Er1-xScxNiSb. To model the energetic and kinetic performances of the semiconductor thermometric material Er1-xScxNiSb, particularly the behavior of the Fermi level F e , bandgap width g e the distribution of the density of electronic states (DOS) and the behavior of its electrical resistance ρ(x, T) is calculated for an ordered variant of the structure in which the Er atoms in position 4a are replaced by Sc atoms. It is shown that the ErNiSb compound is a semiconductor of the electronic conductivity type, in which the Fermi level is located near the level of the conduction band C e . The modeling showed that at higher concentrations of Sc atoms, the number of generated acceptors exceeds the concentration of uncontrolled donors, and the concentration of free holes exceeds the concentration of electrons. Under these conditions, the Fermi level F e approaches, and then the level of the valence band Er1- xScxNiSb crosses: the dielectric-metal conductivity transition occurs. The experiment should change the sign of the thermo-emf coefficient α(x, T) Er1-xScxNiSb from negative to positive, and the intersection of the Fermi level F e and the valence band changes the conductivity from activating to metallic: on the dependences ln(ρ(1/T)) the activation sites disappear, and the values of resistivity ρ increase with temperature.
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Miran, Hussein A., Mohammednoor Altarawneh, Zainab N. Jaf, M. Mahbubur Rahman, Mansour H. Almatarneh, and Zhong-Tao Jiang. "Influence of the variation in the Hubbard parameter (U) on activation energies of CeO2-catalysed reactions." Canadian Journal of Physics 98, no. 4 (April 2020): 385–89. http://dx.doi.org/10.1139/cjp-2019-0065.

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Accurate description of thermodynamic, structural, and electronic properties for bulk and surfaces of ceria (CeO2) necessitates the inclusion of the Hubbard parameter (U) in the density functional theory (DFT) calculations to precisely account for the strongly correlated 4f electrons. Such treatment is a daunting task when attempting to draw a potential energy surface for CeO2-catalyzed reaction. This is due to the inconsistent change in thermo-kinetics parameters of the reaction in reference to the variation in the U values. As an illustrative example, we investigate herein the discrepancy in activation and reaction energies for steps underlying the partial and full hydrogenation of acetylene over the CeO2(111) surface. Overall, we find that both activation and reaction energies positively correlate with the increase in the U value. In addition to benchmarking against more accurate theoretical methodologies, we suggest that U values are better optimized against kinetics modelling of experimentally observed profiles of products from the catalytic-assisted system of reactions.
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Dogru Mert, Basak, Mehmet Erman Mert, Gülfeza Kardas, and Birgül Yazici. "The experimental and quantum chemical investigation for two isomeric compounds as aminopyrazine and 2-amino-pyrimidine against mild steel corrosion." Anti-Corrosion Methods and Materials 63, no. 5 (2016): 369–76. http://dx.doi.org/10.1108/acmm-12-2014-1480.

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Purpose The purpose of this paper is to investigate the adsorption and corrosion inhibition of two isomeric compounds (C4H5N3) as aminopyrazine (AP) and 2-amino-pyrimidine (2AP) on mild steel (MS) in 0.5 M HCl. The study was a trial to combine experimental and modelling studies and research effect of molecular geometry on inhibition effect of inhibitor molecules. Design/methodology/approach The thermodynamic, kinetic and quantum parameters were determined. The electrochemical impedance spectroscopy and anodic polarisation measurements were obtained. The scanning electron microscope was used for monitoring electrode surface. The highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, Mulliken and natural bonding orbital charges on the backbone atoms, absolute electronegativity, absolute hardness were calculated by density functional theory (DFT)/B3LYP/6-311G (++ d,p). Findings Results showed that AP and 2AP suppressed the corrosion rate of MS. The corrosion current values were 0.530, 0.050 and 0.016 mA cm-2 in HCl, AP and 2AP containing HCl solutions, respectively. It was illustrated with the blocked fraction of the MS surface by adsorption of inhibitors which obeyed the Langmuir isotherm. The inhibition efficiency follows the order: 2AP > AP which is in agreement with experimental and quantum results. Originality/value This paper provides lay a bridge on the molecular geometry and inhibition efficiency by electrochemical tests and modelling study. The inhibition effect of AP and 2AP has not been compared with each other, neither experimentally nor theoretically. This study put forward possible application of 2AP as corrosion inhibitor especially for closed-circuit systems.
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Wang, Ying, and Daniel John Blackwood. "Exploring the Kinetics of Oxygen Reduction Reaction in Relation to Pitting Corrosion Resistance in Fe-Cr Alloys." ECS Meeting Abstracts MA2024-01, no. 18 (August 9, 2024): 1241. http://dx.doi.org/10.1149/ma2024-01181241mtgabs.

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Pitting corrosion, a major concern in materials science and engineering, threatens critical metallic structures and components. Its implications reach across daily life and industries such as energy, transportation, and infrastructure, potentially causing environmental harm, economic losses, and even loss of life. This complex process is influenced by factors including material composition, local environment, and mechanical stresses.1 Once initiated, pit propagation rates are largely dependent on the magnitude of the supporting cathodic current available from the oxygen reduction reaction (ORR) occurring on the external passive film.2 In Fe-Cr alloys, the ORR occurs on this film, undergoing a mixed diffusion and kinetic-controlled process. The number of electrons involved and the corrosion rate are determined by the thermodynamically stable state of the passive film. This research studies the ORR kinetics on FeCr alloys fabricated by arc-melting, using both computational and experimental methods. The rotating disc electrode technique was employed across various Fe:Cr alloys in alkaline and neutral electrolytes. The Koutecky-Levich analysis showed a dominant four-electron ORR pathway in all tested Fe-Cr alloys, with the ORR significantly inhibited by higher proportions of Cr2O3 in the film, suggesting a correlation with high chromium content. Experimental ORR overpotentials, when combined with theoretical potential-pH (Pourbaix) diagrams, helped discern the likely characteristics of the passive films on the alloys. It was deduced that the catalytic properties of potential passive films increased in the order Cr2O3 < Fe3O4 < Fe2O3 < FeCr2O4. These findings, excellently aligned with density functional theory (DFT) modelling, underscore the role of increased chromium levels in slowing pitting progression by suppressing the ORR. In summary, this research offers distinctive insights into the correlation between the kinetics of the ORR and the resistance to localized corrosion in Fe-Cr alloys, which enhances our understanding of the underlying mechanisms of pitting corrosion. Keywords FeCr alloy, pitting corrosion, ORR, rotating disc electrode, DFT Reference [1] B. Zhang, J. Wang, B. Wu, X. W. Guo, Y. J. Wang, D. Chen, Y. C. Zhang, K. Du, E. E. Oguzie, and X. L. Ma, Nat. Commun. (2018) 9, 2559. [2] G. T. Burstein, P. C. Pistorius, and S. P. Mattin, Corros. Sci. (1993) 35, 57.
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Jaberi, Ali, Michel L. Trudeau, Jun Song, and Raynald Gauvin. "On the Study of Lithium Diffusivity in Lithium Nickel Manganese Cobalt Oxide Cathodes." ECS Meeting Abstracts MA2022-01, no. 2 (July 7, 2022): 381. http://dx.doi.org/10.1149/ma2022-012381mtgabs.

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Climate change, population growth, and rising fossil fuel prices have encouraged governments and scientists for alternate energy resources. This energy transition requires a high-performance energy storage device to satisfy the high energy and power demand and lithium-ion battery (LIB) is one of the promising one. The performance of these batteries ultimately relies on the properties of their components. In this regard, to meet the high-power demand in high-power applications (such as electric vehicles (EVs) and hybrid EVs), materials with rapid lithium transport are required. Lithium Nickel Manganese Cobalt Oxide (NMC) has attracted scientists’ attentions due to its outstanding performance as a cathode material. Therefore, understanding the effect of various factors on lithium diffusivity in NMC is critical to develop high-performance LIBs for high-power applications. Electrochemical methods such as potentiostatic and galvanostatic intermittent titration techniques (PITT and GITT) have been frequently utilized to experimentally quantify lithium diffusivity in NMC. These techniques need the knowledge of electrode particle shape and dimension, and uncertainty about these parameters leads to substantial errors in predicting the diffusion coefficient. In addition, because these techniques consider the response of the whole electrochemical cell, it is hard to distinguish the effect of different structural factors on Li diffusivity in a single NMC active material. Therefore, an appropriate method still needs to be developed to capture the structural effects on lithium diffusivity in NMC. For this purpose, a multi-level modelling from Density Functional Theory (DFT) to kinetic Monte Carlo (KMC) should be implemented. In this study, we will use DFT to find the ground state energy of NMC at different lithium concentrations and configurations. Also, the minimum energy path of lithium migration and the related activation barrier will be found by Climbing Image-Nudge Elastic Band (CI-NEB) method. Then by implementing the configurational dependent activation barrier into the KMC simulation, the lithium diffusivity will be studied. This atomistic simulation gives insight about the structural effects on lithium diffusivity in NMC to further develop this cathode material for high performance LIBs.
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Luisier, Mathieu, Jan Aeschlimann, Jonathan Backman, Jiang Cao, Manasa Kaniselvan, Youseung Lee, and Marko Mladenovic. "(Invited) Advanced Modeling of Nanoscale Devices." ECS Meeting Abstracts MA2023-01, no. 33 (August 28, 2023): 1849. http://dx.doi.org/10.1149/ma2023-01331849mtgabs.

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Moore’s scaling law has survived during more than 50 years because the transistor fabrication recipes have been continuously adapted and technology boosters have been gradually introduced, e.g. strain, high- dielectrics, or 3-D FinFETs. The driving force behind these innovations has always been the intuition of clever researchers who benefited from classical technology computer aided design (TCAD) tools. The latter have been used in the semiconductor industry since the end of the 1970’s, when the first 2-D simulations of CMOS devices became feasible on a supercomputer [1]. Over the last 40 years, transistors have undergone tremendous evolutions, their dimensions being reduced by several orders of magnitude, while the physical models at the core of commercially available device simulators have remained the same: electron transport is still described by classical drift-diffusion (DD) equations, which have been modified to capture parts of the quantum mechanical effects affecting nano-transistors, e.g. geometrical confinement tunnelling leakages, or energy quantization [2]. A new generation of advanced TCAD tools that go beyond the DD equations and rely on atomistic quantum mechanical concepts is needed to reproduce the characteristics of today’s nanostructures and to predict the performance of not-yet-fabricated components. Such tools should combine different modelling approaches to be able to treat various device types, from state-of-the-art nano-transistors to photo-detectors based on two-dimensional materials or resistive switching random access memories. For example, to shed light on the behaviour of valence change memory (VCM) cells, which consist of metal-insulator-metal stacks, molecular dynamics (MD), kinetic Monte Carlo (KMC), density functional theory (DFT), and quantum transport (QT) should be allied, as illustrated in the accompanying figure. By doing so, the growth of nano-filaments through realistic oxides embedded between two metallic electrodes can be accurately simulated and the electrical current flowing through computed with, e.g., the Non-equilibrium Green’s Function (NEGF) formalism [3]. In this presentation the multi-method simulation environment shown the accompanying Figure will be briefly reviewed. The main focus will be set on the discussion of few applications, among them transistors and memory cells. References: [1] S. Selberherr, W. Fichtner, and H.W. Potzl, “Minimos - A program package to facilitate MOS device design and analysis”, Proceedings of NASECODE I, 275 (1979). [2] A. Wettstein, A. Schenk, and W. Fichtner, “Quantum device-simulation with the density-gradient model on unstructured grids”, IEEE Trans. On Elec. Dev. 48, 279 (2001). [3] M. Kaniselvan, M. Luisier, and M. Mladenovic, “An Atomistic Modelling Framework for Valence Change Memory Cells”, Solid-State Electronics 199, 108506 (2023). Figure Caption: Multi-method simulation framework dedicated to the investigation of resistive switching devices, here valence change memory (VCM) cells. First, oxide samples with a low defect concentration are constructed withclassical molecular dynamics (MD) using a melt-and-quench procedure. They arethentransferredto akinetic Monte Carlo (KMC) solver that determines the distribution of oxygen vacancies (VO,green spheres) within the oxide layer. All input parameters to KMC (diffusioncoefficients and generation/recombination rates) are computed with density functional theory(DFT), which is also used to calculate the Hamiltonian (H) and Overlap (S) matrices of the created VCM structure. Finally, these quantities are passed to aquantum transport (QT) tool to perform ab initiodevice simulations. Figure 1
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Homma, Takayuki, Masahiro Kunimoto, and Masahiro Yanagisawa. "(Invited) Approaches for Mechanistic Understanding of Electrodeposition Processes for Fabricating Micro/Nano Structures and Devices." ECS Meeting Abstracts MA2023-01, no. 27 (August 28, 2023): 1757. http://dx.doi.org/10.1149/ma2023-01271757mtgabs.

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Electrochemical deposition processes have precise controllability, selectivity and uniformity, and have been widely applied for fabricating various functional micro/nano structures and devices. In order to achieve further higher controllability for developing reliable process for manufacturing, molecular-level understanding of the deposition processes is required. Furthermore, this can be be also utilized to understand various applications such as the electrode processes of secondary batteries using metal anodes and so on. For this, we have attempted to apply theoretical approaches such as density functional theory (DFT) and kinetic Monte Carlo (KMC) calculations[1.2], as well as experimental methods such as surface enhanced Raman microscopy equipped with plasmonic sensors[3-5]. In this paper, these approaches with some of the resent results will be described. The analysis using DFT calculations provided the molecular-level insights for the catalytic activity of the electroless deposition reaction process at the surface, with the effects of the additive species and solvation. Also, in combination with the KMC calculation, multi-scale simulation for the nucleation and growth process at the Zn anode surface for the secondary battery was attempted. While these approaches enable quantitative discussion for the mechanistic understanding of the processes, we also attempted to obtain "real" data from experimental approaches. For this, we applied surface enhanced Raman scattering (SERS) and developed "plasmonic sensors" with controlled nanostructures to obtain high signal enhancement at electrode-electrolyte interface. We have developed two types of the plasmonic sensors which could achieve extremely high sensitivity. Multi-confocal type SERS microscopy was also developed for mapping and imaging analyses of the electrode surface as well as local pH distributions. By using these techniques, various processes at the electrode surfaces and interfaces have been investigated and modelling of the processes has been carried out. This work was financially supported in part by “Development of Systems and Technology for Advanced Measurement and Analysis” program from Japan Science and Technology Agency, and Grant-in-Aid for Scientific Research, MEXT, Japan. [1] Y. Onabuta, M. Kunimoto, H. Nakai, T. Homma, Electrochim. Acta, 307, 536 (2019). [2] Y. Onabuta, M. Kunimoto, S. Wang, Y. Fukunaka, H. Nakai, T. Homma, J. Electrochem. Soc., 169, 092504 (2022). [3] M. Yanagisawa, M. Saito, M. Kunimoto, T. Homma, Appl. Phys. Express, 9 , 122002 (2016). [4] M. Kunimoto, F. Yamaguchi, M. Yanagisawa, T. Homma, J. Electrochem. Soc., 166, D212 (2019). [5] T. Wang, M. Kunimoto, M. Yanagisawa, M. Morita, T. Abe, T. Homma, Energy Env. Mat., in press (2022).
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Дисертації з теми "Kinetic modelling, density functional theory (DFT)"

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Vorms, Evgeniia. "Cinétique de l’oxydation de l’hydrate d’hydrazine et d’autres combustibles sans carbone sur électrode de nickel." Electronic Thesis or Diss., Strasbourg, 2025. http://www.theses.fr/2025STRAF003.

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La production d'énergie électrochimique à partir de combustibles sans carbone a récemment suscité un grand intérêt. Ce manuscrit se concentre sur l'étude du mécanisme de la réaction d'oxydation de l'hydrazine (HHOR) sur des électrodes de Ni et le compare avec ceux des réactions d'oxydation du borohydrure et de l’ammoniac-borane (BOR, ABOR). Les sites métalliques de Ni ont été identifiés comme les sites catalytiques pour la HHOR, la BOR et l'ABOR, tandis que la présence de sites de Ni (hydr)oxydés a un effet négatif sur l'activité sans influencer clairement le mécanisme réactionnel. Sur la base des résultats de calculs DFT, de la modélisation microcinétique et de mesures DEMS en ligne, un mécanisme de la HHOR sur Ni a été proposé. Celui-ci implique la réaction directe de l'hydrazine dissoute avec des espèces Ni-OH adsorbées, formant un intermédiaire N2Hx,ad (x<4), qui est ensuite oxydé électrochimiquement, conduisant à la formation de N2 et d’eau
Electrochemical energy production from carbon-free fuels has recently attracted much attention. This manuscript focuses on studying the mechanism of the hydrazine oxidation reaction (HHOR) on Ni electrodes and comparing it with the ones of the borohydride and ammonia-borane oxidation reactions (BOR, ABOR). Metallic Ni sites were identified as the catalytic sites for the HHOR, BOR, and ABOR, while the presence of Ni (hydr)oxide sites was found to negatively affect activity without a clear influence on the reaction mechanism. Based on the results of DFT calculations, microkinetic modelling, and online DEMS measurements, a mechanism for HHOR on Ni was proposed. It involves the direct reaction of dissolved hydrazine with adsorbed Ni-OH species forming N2Hx,ad (x<4) intermediate, which is subsequently electrochemically oxidized, leading to the formation of N2 and water
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2

Gonzalez, Calderon Juan David. "Molecular and Kinetic Modelling of the Ammonia Oxidation on Platinum." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17683.

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The thesis contributes to the fundamental understanding of the chemistry of ammonia oxidation on platinum. The research concentrates on determining the kinetic and reaction mechanisms for the NH3(g) oxidation with O2(g) on flat and stepped platinum surfaces using first-principles methodologies. The research finds direct applications in the modelling of the NO(g) production from NH3(g), a significant key step in the HNO¬3 manufacture through the Ostwald process. This process is industrially very significant because nearly all of the world's HNO3 is made from NH3(g), and most of the world’s HNO3 production is dedicated to the production of fertilisers. The reactions studied in this work, however, are relevant to other chemical processes of interest such as the selective catalytic oxidation for the removal of NH3(g) from industrial waste streams, and the selective catalytic reduction of NOx. The work carried out seeks fundamental analysis of three main elements of the NH3(g) oxidation, i) the effect of Pt surface morphology towards the formation of N2O(g), ii) the existence of lower activated alternative pathways for NO(g) formation and iii) the effect of the surface coverage on the energetics of selected surface reactions and the adsorption/desorption process. A new thermodynamically-consistent microkinetic model for the NH3(g) oxidation over Pt has been proposed by using the DFT-calculated kinetic parameters on the Pt(211) surface as input parameters. The simulated profiles of NH3(g) conversion and product yields reproduce qualitatively the experimental data obtained previously in our group, for the NH3(g) oxidation over Pt using a micro–tubular reactor. However, sensitivity analysis of the input data suggests small changes to a selected set of values improve the quantitative agreement with experimental observations.
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3

O'Kennedy, Sean James. "A kinetic and thermodynamic study of procyanidin oligomer conformation by 1H NMR and DFT." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/98054.

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Razumovskiy, Vsevolod. "Thermodynamic and kinetic properties of Fe-Cr and TiC-ZrC alloys from Density Functional Theory." Doctoral thesis, KTH, Materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96285.

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The complete and accurate thermodynamic and kinetic description of any systemis crucialfor understanding and predicting its properties. A particular interest is in systemsthat are used for some practical applications and have to be constantly improved usingmodification of their composition and structure. This task can be quite accuratelysolved at a fundamental level by density functional theory methods. Thesemethods areapplied to two practically important systems Fe-Cr and TiC-ZrC.The elastic properties of pure iron and substitutionally disordered Fe-Cr alloy are investigatedas a function of temperature and concentration using first-principles electronicstructurecalculations by the exact muffin-tin orbitals method. The temperature effectson the elastic properties are included via the electronic, magnetic, and lattice expansioncontributions. It is shown that the degree of magnetic order in both pure iron andFe90Cr10 alloy mainly determines the dramatic change of the elastic anisotropy of thesematerials at elevated temperatures. A peculiarity in the concentration dependence ofthe elastic constants in Fe-rich alloys is demonstrated and related to a change in theFermi surface topology.A thermodynamic model for the magnetic alloys is developed from first principles andapplied to the calculation of bcc Fe-Cr phase diagram. Various contributions to the freeenergy (magnetic, electronic, and phonon) are estimated and included in the model. Inparticular, it is found that magnetic short range order effects are important just abovethe Curie temperature. The model is applied for calculating phase equilibria in disorderedbcc Fe-Cr alloys. Model calculations reproduce a feature known as a Nishizawahorn for the Fe-rich high-temperature part of the phase diagram.The investigation of the TiC-ZrC system includes a detailed study of the defect formationenergies and migration barriers of point defects and defect complexes involvedin the diffusion process. It is found, using ab initio atomistic simulations of vacancymediateddiffusion processes in TiC and ZrC, that a special self-diffusion mechanism isoperative for metal atom diffusion in sub-stoichiometric carbides. It involves a noveltype of a stable point defect, a metal vacancy ”dressed” in a shell of carbon vacancies.It is shown that this vacancy cluster is strongly bound and can propagate through thelattice without dissociating.

QC 20120604


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5

Afaneh, Akef. "Computational investigations of the electronic structure of molecular mercury compounds: ion-selective sensors." Springer International Publishing AG, 2012. http://hdl.handle.net/1993/30661.

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This thesis presents the basic concepts of electronic structure theory and the chemical properties of mercury. The theoretical foundation of DFT and the consequences of relativity are also introduced. The electronic structure of Hg(II) ions, [Hg(L)n(H2O)m]q (L = HO-, Cl-, HS-, S2-) has been studied. We show, in this thesis, that the charge transfer (that is calculated from the hard-soft-acid-base principle (Pearson’s principle)), the total NBO charge and the interaction energies are strongly correlated. Our studies indicate the effect of the solvent on the global electrophilicity, the charge transfer and consequently the interaction strength between Hg(II) and ligand L. The formation constants, logK, of Hg2+−complexes are calculated. The procedure that we follow in this thesis to calculate the formation constants, logK’s, are in good agreement with the extrapolated experimental values. We introduce and explain why it is important adding water molecules explicitly during the calculations of the logK. The recommended logK value of HgS is 27.2. We examined two different types of organic compounds as sensors for heavy metal ions: lumazine (Lm) and 6-thienyllumazine (TLm). We found that the simple calculation of pKa values using DFT methods and implicit solvent models failed to reproduce the experimental values. However, calculated orbital energies and gas phase acidities both indicate that the compound TLm is inherently more acidic than the parent species Lm. We demonstrate that: (1) we need to take in our consideration the population of each tautomer and conformer during the calculations of the pKa values, and (2) thienyl group has indirect effect on the acidity of the proton on N1 in the uracil ring. Last but not least, the fluorescence spectrum of the sensors (L) and their [(L)nM(H2O)m]2+ complexes (L = Lumazine (Lm) and 6-thienyllumazine (TLm) and M = Cd2+and Hg2+) are calculated using time dependent DFT (TDDFT). The results show that TDDFT is in good agreement with experimental results. This chapter provides a new concept in the design of fluorescence turn-on/off sensors that has wider applicability for other systems. Finally, we provide a summary of the works compiled in this thesis and an outlook on potential future work.
October 2015
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Baniahmad, Ata. "QUANTUM MECHANICAL Study and Modelling of MOLECULAR ELECTRONIC DEVICES." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13193/.

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Molecular electronics pursues the use of molecules as fundamental electronic components. The inherent properties of molecules such as nano-size, low cost, scalability, and self-assembly are seen by many as a perfect complement to conventional silicon electronics. Molecule based electronics has captured the attention of a broad cross section of the scientific community. In molecular electronic devices, the possibility of having channels that are just one atomic layer thick, is perhaps the most attractive feature that takes the attention to graphene.The conductivity, stability, uniformity, composition, and 2D nature of graphene make it an excellent material for electronic devices. In this thesis we focused on Zigzag Graphene NanoRibbon(ZGNR) as a transmission channel. Due to the importance of an accurate description of the quantum effects in the operation of graphene devices, a full-quantum transport model has been adopted: the electron dynamics has been described by Density Functional Theory(DFT) and transport has been solved within the formalism of Non-Equilibrium Green’s Functions (NEGF). Using DFT and NEGF methods, the transport properties of ZGNR and ZGNR doped with Si are studied by systematically computing the transmission spectrum. It is observed that Si barrier destroyed the electronic transport properties of ZGNR, an energy gap appeared for ZGNR, and variations from conductor to semiconductor are displayed. Its followed by a ZGNR grown on a SiO2 crystal substrate, while substituting the Graphene electrodes with the Gold ones, and its effect on transmission properties have been studied. Improvement in transmission properties observed due to the formation of C-O bonds between ZGNR and substrate that make the ZGNR corrugated. Finally, we modeled a nano-scale Field Effect Transistor by implementing a gate under SiO2 substrate. A very good I-ON/I-OFF ratio has been observed although the device thickness.
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Nour, Zalfa. "Modélisation de l'adsorption des molécules à fort impact sur l'environnement et la santé dans des matériaux nanoporeux en couplant des approches quantiques et classiques." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2011. http://www.theses.fr/2011ENCM0001/document.

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L'adsorption de CO dans la faujasite échangée au CuI et au Na+ a été modélisée à l'aide des approches quantiques (DFT) et classiques (Monte Carlo). Grâce à l'approche DFT, la surface d'énergie potentielle de la faujasite a été explorée. Différents types d'interactions de CO avec les cations ont été identifiés, pour chacune les effets induits par l'adsorption de CO aux niveaux structural et énergétique ont été analysés, et le calcul de la fréquence de vibration de CO a été réalisé. Grâce aux valeurs obtenues, une nouvelle attribution des spectres d'adsorption de CO dans CuY et NaY a été établie. D'un autre côté, grâce aux simulations Monte Carlo dans l'ensemble Grand Canonique, les propriétés d'adsorption (isothermes et enthalpies) de la faujasite vis-à-vis de CO ont été modélisées, et le mécanisme microscopique d'adsorption de CO a été établi. La mise en œuvre de ces simulations a nécessité de paramétrer un nouveau champ de force destiné à décrire les interactions CO/faujasite et CO/CO
CO adsorption in CuI and Na+ exchanged faujasite has been modeled by mean of quantum (DFT) and classical (Monte Carlo) approaches. By mean of the DFT calculations, faujasite potential energy surface has been explored. Different types of CO interactions with the cations have been highlighted, for each one of them CO adsorption effects on the structural and energetic parameters have been analyzed, and calculations of the CO stretching frequency have been performed. Thanks to our calculated values, a new attribution of CO adsorption spectra in CuY and NaY has been established. On another side, by mean of Monte Carlo simulations in the Grand Canonical ensemble, faujasite adsorption properties regarding CO (isotherms and enthalpies) have been modeled, and the CO adsorption mechanism has been established at the microscopic level. The implementation of these simulations has required the derivation of a new force field describing the CO/faujasite and CO/CO interactions
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COMISSO, ALESSIO. "MODELLING THE SELF-ASSEMBLY OF SUPRAMOLECULAR NANOSTRUCTURES ADSORBED ON METALLIC SUBSTRATES." Doctoral thesis, 2007. http://hdl.handle.net/10077/2528.

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2005/2006
The term Nanotechnology is used to describe a variety of techniques to fabricate materials and devices at the nanoscale. Nano-techniques include those used for fabrication of nanowires, those used in semiconductor fabrication such as deep ultraviolet and electron beam lithography, focused ion beam machining, nanoimprint lithography, atomic layer deposition, molecular vapor deposition, and the ones including molecular self-assembly techniques. All these methods are still being developed and not all of them were devised with the sole purpose of creating devices for nanotechnology. A number of physical phenomena become noticeably pronounced as the system size decreases. These include statistical effects, as well as quantum effects, where the electronic properties of solids are altered if the particle size is greatly reduced. There are also effects which never come into play by going from macro to micro dimensions, while they become dominant when the nanometer scale is reached. Furthermore nanotechnology can be thought of as extensions of traditional disciplines towards the explicit consideration of all these effects. Traditional disciplines can be re-interpreted as specific applications of nanotechnology. Broadly speaking, nanotechnology is the synthesis and application of ideas from science and engineering towards the understanding and production of novel materials and devices with atomicscale control. Modern synthetic chemistry has reached the point where it is possible to prepare small molecules of almost any (stable) structure. Methods exist today to produce a wide variety of useful chemicals. A branch of nanotechnology, relevant to the present thesis work, is looking for methods to assemble single molecules into supramolecular assemblies arranged in a well defined manner. These approaches use molecular self-assembly and supramolecular chemistry to automatically arrange the single molecules into interesting and potentially useful structures. The scanning tunneling microscope (STM) is a non-optical microscope that scans an electrical probe (the tip) over a conductive surface to be imaged. It allows scientists to visualize regions of high electron density at the atomic scale, and hence infer the position of individual atoms and molecules on a material surface. STM is specially suited for the study of the self-assembly of molecules deposited on conductive substrates because it provides direct insight into the assembled structures. However, the STM images are often insufficient for a complete description of the phenomena, and computer simulations offer a complementary approach that can effectively integrate the experiments . The theoretical investigation of the molecular self-assembly aims at the understanding of the mechanisms that are involved in the assemblies formatiom. In particular the atomistic simulation can provide information on the geometry of the stable structures, the nature and the intensity of the interactions as well as on the dynamical processes. In this thesis, a combination of first principles and classical molecular dynamics simulations is used to shed light on the self-assembly of some organic molecules deposited on noble metal substrates. Three cases are discussed, the self-assembly of TMA and BTA molecules on Ag(111) and the self-assembly of an oxalic amide derivative on Au(111). When TMA and BTA molecules are deposited onto a silver surface at a temperature lower than room temperature they form a regular 2D honeycomb network featuring double hydrogen bonds between carboxylic groups. Even if this bonding makes the network very stable, when these systems are annealed to higher temperatures they undergo some irreversible phase transition into closer-packed supramolecular arrangements. Namely, the TMA has a transition from honeycomb to a high coverage “quartet” structure and the BTA has two transtions: from honeycomb to unidimensional stripes and from here to a closed-packed monolayer. A combination of experimental and theoretical techniques allowed us to identify the stepwise deprotonation of the carboxylic acid groups as the driving force driving the phase transitions. Our theoretical investigation targeted the electrostatic interaction involved in the formation of the various phases revealing that a depolarisation of the molecular ions occurs as a consequence of the deprotonation process. Therefore, the repulsive contribution arising from the interaction of negatively charged molecules can be overcome by the attractive hydrogen bond interaction involving the deprotonated carboxylic groups, thus resulting in a stable closed-packed arrangement. Rather remarkably, this exemplifies how higher-coverage phases can be obtained at each step of a series of phase transitions in a supramolecular assembled system, despite the increasing temperature and the increasing electrostatic repulsive energy cost accompanying deprotonation. The oxalic amide derivative molecules arranges themselves in linear chains both in the molecular solid and when adsorbed on a gold surface. However the intermolecular distance and the geometry of the chains are different in these two cases. Various relaxed bonding structure between molecules in the chains have been calculated from first principles in the present work. The rationale of the different linkage behaviour between molecules in the two situations described have also been investigated: the interaction with the substrate appears to be the main cause for the particular rearrangement observed in the chains. Both experimental observations and theoretical predictions indicate that a conformational change involving the rotation of the phenyl rings of the monomers is necessary for chain formation.
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Hapka, Michał. "Expanding the predictive power of DFT: modelling of gold complexes and noncovalent open-shell interactions." Doctoral thesis, 2015. https://depotuw.ceon.pl/handle/item/1312.

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Praca doktorska mgra Michała Hapki prezentuje rozwój metodologii oraz zastosowań teorii funkcjonału gęstości elektronowej (DFT). W części poświęconej rozwojowi metodologii wprowadzone zostały dwa nowe sformułowania rachunku zaburzeń o adaptowanej symetrii (SAPT) oparte o opis oddziałujących monomerów metodą Kohna-Shama. Pierwsze z nich wykorzystuje opis monomerów przy pomocy funkcjonałów gęstości elektronowej o poprawnej asymptotyce (LRC od ang. long-range corrected functionals). Wprowadzona metoda LRC-SAPT łaczy w sobie korzyści wynikające z zapewnienia poprawnego asymptotycznego zachowania potencjału korelacyjno-wymiennego, jak również minimalizacji tzw. błędu delokalizacji elektronowej (DE). Drugi z wprowadzonych formalizmów, SAPT(UKS), umożliwia obliczenia energii oddziaływania niekowalencyjnie związanych wysokospinowych dimerów o charakterze otwartopowłokowym w oparciu o opis monomerów przy pomocy nieograniczonej metody Kohna-Shama (UKS, od ang. unrestricted Kohn-Sham). Metoda SAPT(UKS) stanowi atrakcyjną alternatywę dla zaproponowanego przez Żuchowskiego i wsp. [JCP, 129, 084101 (2008)] podejścia SAPT(ROKS). W części poświęconej zastosowaniom DFT przedstawiono badania skupione na wykorzystaniu tej teorii w opisie wybranych aspektów chemii związków złota. Po pierwsze, opracowano metodologię obliczania energii oddziaływania w kompleksach klastrów złota stabilizowanych ligandami. Wykazano, że zaproponowane podejście oparte o minimalizację DE oraz uwzględnienie oddziaływań dyspersyjnych pozwala na wiarygodny opis oddziaływań donorowo-akceptorowych w tej klasie związków. Po drugie, przedstawiono obliczenia absorpcyjnych widm UV klastrów złota Au(n) (n = 4, 6, 8, 12, 20) w ramach zależnej od czasu metody funkcjonału gęstości elektronowej, TD-DFT. W tym celu po raz pierwszy wykorzystano funkcjonały LRC. Wykazano, że zarówno poprawne asymptotyczne zachowanie potencjału korelacyjno-wymiennego jak również obecność dokładnej, krótkozasięgowej wymiany są niezbędne do poprawnego opisu własności optycznych klastrów złota. Ostatnia z prac zaprezentowanych w części aplikacyjnej dotyczyła syntezy oraz charakterystyki szeregu kompleksów złota wykazujących tzw. bezmostkowe oddziaływania aurofilowe. Opisano trzy nowe sole: [Au(H2-mmta)2]3H2O (1), Na3[Au(mmta)2]6H2O (2) oraz Na3[Au(mmta)2]10.5H2O (3), (H2-mmta = kwas 2-merkapto-4-metylo-5-tiazolowy). Struktury otrzymanych związków określone na podstawie analizy krystalograficznej pozwoliły zidentyfikować obecność aurofilowych dimerów [Au2(H2-mmta)4](2+) w przypadku 1 oraz [Au2(mmta)4](6-) w przypadku struktur 2 oraz 3. Analiza z wykorzystaniem szeregu metod DFT pozwoliła na charakterystkę słabych oddziaływań stabilizujących konformacje otrzymanych związków.
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(11159943), Pilsun Yoo. "INVESTIGATION OF CHEMISTRY IN MATERIALS USING FIRST-PRINCIPLES METHODS AND MACHINE LEARNING FORCE FIELDS." Thesis, 2021.

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The first-principles methods such as density functional theory (DFT) often produce quantitative predictions for physics and chemistry of materials with explicit descriptions of electron’s behavior. We were able to provide information of electronic structures with chemical doping and metal-insulator transition of rare-earth nickelates that cannot be easily accessible with experimental characterizations. Moreover, combining with mean-field microkinetic modeling, we utilized the DFT energetics to model water gas shift reactions catalyzed by Fe3O4at steady-state and determined favorable reaction mechanism. However, the high computational costs of DFT calculations make it impossible to investigate complex chemical processes with hundreds of elementary steps with more than thousands of atoms for realistic systems. The study of molecular high energy (HE) materials using the reactive force field (ReaxFF) has contributed to understand chemically induced detonation process with nanoscale defects as well as defect-free systems. However, the reduced accuracy of the force fields canalso lead to a different conclusion compared to DFT calculations and experimental results. Machine learning force field is a promising alternative to work with comparable simulation size and speed of ReaxFF while maintaining accuracy of DFT. In this respect, we developed a neural network reactive force field (NNRF) that was iteratively parameterized with DFT calculations to solve problems of ReaxFF. We built an efficient and accurate NNRF for complex decomposition reaction of HE materials such as high energy nitramine 1,3,5-Trinitroperhydro-1,3,5-triazine (RDX)and predicted consistent results for experimental findings. This work aims to demonstrate the approaches to clarify the reaction details of materials using the first-principles methods and machine learning force fields to guide quantitative predictions of complex chemical process.
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Книги з теми "Kinetic modelling, density functional theory (DFT)"

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Eriksson, Olle, Anders Bergman, Lars Bergqvist, and Johan Hellsvik. Density Functional Theory. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198788669.003.0001.

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Density functional theory (DFT) has established itself as a very capable platform for modelling from first principles electronic, optical, mechanical and structural properties of materials. Starting out from the Dirac equation for the many-body system of electrons and nuclei, an effective theory has been developed allowing for materials specific and parameter free simulations of non-magnetic and magnetic solid matter. In this Chapter an introduction will be given to DFT, the Hohenberg-Kohn theorems, the Kohn-Sham equation, and the formalism for how to deal with non-collinear magnetism.
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Частини книг з теми "Kinetic modelling, density functional theory (DFT)"

1

Sharma, A. K., Gokul Ram Nishad, P. K. Vishwakarma, and P. S. Jaget. "Density functional theory (DFT)-based molecular modeling." In Computational Modelling and Simulations for Designing of Corrosion Inhibitors, 115–33. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-323-95161-6.00001-1.

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Polak, Elias, Kimberly J. Daas, and Stefan Vuckovic. "The adiabatic connection formalism in DFT – theory and practice." In Chemical Modelling, 1–17. Royal Society of Chemistry, 2024. https://doi.org/10.1039/9781837672554-00001.

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The adiabatic connection formalism yielding an exact expression to exchange–correlation functional, has been instrumental in building DFT approximations. Here, we derive and analyze the density-fixed adiabatic connection (AC), which gives an exact expression of the DFT’s exchange–correlation functional. We give an outline of the exact features of the key AC quantities, yielding physical constraints for constructing approximations to the exchange–correlation functional. Lastly, inspired by recent progress in the AC developments in wave function theories, we discuss the similarities and differences between the AC in DFT and wave function formalisms.
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Raissi, Hanen, Imen Chérif, Hajer Ayachi, Ayoub Haj Said, Fredj Hassen, Sahbi Ayachi, and Taoufik Boubaker. "Structure-Property Relationships in Benzofurazan Derivatives: A Combined Experimental and DFT/TD-DFT Investigation." In Density Functional Theory - Recent Advances, New Perspectives and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99246.

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In this work we seek to understand and to quantify the reactivity of benzofurazan derivatives toward secondary cyclic amines, like pyrrolidine, piperidine and morpholine, acting as nucleophile groups in SNAr reactions. For this aim, physico-chemical and structural descriptors were determined experimentally and theoretically using the DFT/B3LYP/6-31+ g (d,p) methodology. Thus, different 4-X-7-nitrobenzofurazans (X = OCH3, OC6H5 and Cl) and products corresponding to the electrophilic aromatic substitution by pyrrolidine, piperidine and morpholine, were investigated. Particularly, the HOMO and LUMO energy levels of the studied compounds, determined by Cyclic Voltammetry (CV) and DFT calculations, were used to evaluate the electrophilicity index (ω). The latter was exploited, according to Parr’s approach, to develop a relationship which rationalizes the kinetic data previously reported for the reactions of the 4-X-7-nitrobenzofurazans with nucleophiles cited above. Moreover, the Parr’s electrophilicity index (ω) of these benzofurazans determined in this work were combined with their electrophilicity parameters (E), reported in preceding papers, was found to predict the unknown electrophilicity parameters E of 4-piperidino, 4-morpholino and 4-pyrrolidino-7-nitrobenzofurazan. In addition, the relationship between the Parr’s electrophilicity index (ω) and Hammett constants σ, has been used as a good model to predict the electronic effect of the nucleophile groups. Finally, we will subsequently compare the electrophilicity index (ω) and the electrophilicity parameters (E) of these series of 7-X-4-nitrobenzofurazans with the calculated dipole moment (μ) in order to elucidate general relationships between E, ω and μ.
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Kusunoki, Masami. "Distinct Roles of the Principal Exchange-Correlation Energy and the Secondary Correlation Energy Functionals in the MGC-SDFT-UHFD Decoupling." In Density Functional Theory - New Perspectives and Applications [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.111746.

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The Kohn-Sham formalism for the density functional theory (DFT) proposed a half-century ago has been the extensive motive force for the material science community, despite it is incomplete because of its problematic notion of eternally-unknown correlation energy functional including a separated part of kinetic energy. Here, we widely explain an alternative method recently discovered by us, i.e. the multiple grand canonical spin DFT (MGC-SDFT) in the unrestricted Hartree-Fock-Dirac (MGC-SDFT-UHFD) approximation. It is proved that the correlation energy functional consists of well-defined principal and secondary parts: the former yields the principal internal energy functional responsible for a set of the one-body quasi-particle spectra defined by the respective ground and excited states with each natural LCAO-MO as well as a set of the expected values of Heisenberg spin Hamiltonian, and the latter does a well-defined spin-dependent perturbation energy responsible for some many-body effects. An application will be made to explain why the water-splitting S1-state Mn4CaO5-clusters in photosystem II can exhibit two different EPR signals, called “g4.8” and “g12-multiline”. Moreover, the secondary correlation energy part will be shown to promote Cooper-pairings of Bloch-electrons near Fermi level in the superconductor, provided that their eigenstates might be exactly determined by the MGC-SDFT-UHFD method.
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Banjare, Manoj Kumar, Kamalakanta Behera, and Ramesh Kumar Banjare. "Electrochemical principles of corrosion inhibition: fundamental and computational aspects of density functional theory (DFT)." In Computational Modelling and Simulations for Designing of Corrosion Inhibitors, 243–69. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-323-95161-6.00007-2.

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Rahman, Shofiur, Paris E. Georghiou, and Abdullah Alodhayb. "Density functional theory (DFT) models for the desulfurization and extraction of sulfur compounds from fuel oils using ionic liquids." In Modelling of Chemical Process Systems, 53–90. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-12-823869-1.00011-9.

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