How Well Can Hybrid Density Functional Methods Predict Transition State Geometries and Barrier Heights?

Lynch, Benjamin J.; Truhlar, Donald G.

doi:10.1021/jp004262z

Cited by 575 publications

(533 citation statements)

References 36 publications

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“…An increase in the exact Hartree-Fock exchange from 0% in pure DFT to 20% in B3LYP to 50% in BHLYP leads to better error cancellation between the reactants and transition states for the computation of barrier heights. 80,82,83 Using restricted orbitals causes most of the DFT barrier heights ∆E ‡ to increase. This significantly improves results for the reaction of H 2 with H, but for the other two symmetric reactions the RBHLYP barriers are overestimated compared to RCCSD(T).…”

Section: Symmetric Reactionsmentioning

confidence: 99%

High-Level ab Initio Studies of Hydrogen Abstraction from Prototype Hydrocarbon Systems

et al. 2006

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Symmetric and non-symmetric hydrogen abstraction reactions are studied using stateof-the-art ab initio electronic structure methods. Second-order Møller-Plesset perturbation theory (MP2) and the coupled-cluster singles, doubles and perturbative triples [CCSD(T)] methods with large correlation consistent basis sets (cc-pVXZ, where X = D,T,Q) are used in determining the transition-state geometries, activation barriers, and thermodynamic properties of several representative hydrogen abstraction reactions. The importance of basis set, electron correlation, and choice of zeroth-order reference wavefunction in the accurate prediction of activation barriers and reaction enthalpies are also investigated. The ethynyl radical (·CCH), which has a very high affinity for hydrogen atoms, is studied as a prototype hydrogen abstraction agent. Our high-level quantum mechanical computations indicate that hydrogen abstraction using the ethynyl radical has an activation energy of less than 3 kcal mol −1 for * To whom correspondence should be addressed. E-mail addresses: sherrill@gatech.edu; merkle@cc.gatech.edu; rfreitas@rfreitas.com 1 hydrogens bonded to an sp 2 or sp 3 carbon. These low activation barriers further corroborate previous studies suggesting that ethynyl-type radicals would make good tooltips for abstracting hydrogens from diamondoid surfaces during mechanosynthesis. Modeling the diamond C(111) surface with isobutane and treating the ethynyl radical as a tooltip, hydrogen abstraction in this reaction is predicted to be barrierless.

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Section: Symmetric Reactionsmentioning

confidence: 99%

High-Level ab Initio Studies of Hydrogen Abstraction from Prototype Hydrocarbon Systems

et al. 2006

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“…Reaction pathways were investigated using density functional theory (DFT) with Truhlar's (U)M06-2X functional [24,25], in conjunction with a 6-311+G(d,p) basis set. Mardirossian and HeadGordon [26] have recently shown that M06-2X provides good overall performance for reaction thermochemistry.…”

Section: Methodsmentioning

confidence: 99%

“…A number of previous investigations have shown that small aromatic molecules can form via cyclisation of unsaturated hydrocarbons (e.g., 1,3,5-hexatriene [28], hexachloropropene [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]). …”

Section: Reaction Initiationmentioning

confidence: 99%

Formation of chlorobenzenes by oxidative thermal decomposition of 1,3-dichloropropene

Ahubelem

Shah

Moghtaderi

et al. 2015

Combustion and Flame

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We combine combustion experiments and density functional theory (DFT) calculations to investigate the formation of chlorobenzenes from oxidative thermal decomposition of 1,3-dichloropropene.Mono-to hexa-chlorobenzenes are observed between 800 and 1150 K, and the extent of chlorination was proportional to the combustion temperature. Higher chlorinated congeners of chlorobenzene (tetra-, penta-, hexa-chlorobenzene) are only observed in trace amounts between 950 and 1050 K.DFT calculations indicate that cyclisation of chlorinated hexatrienes proceeds via open-shell radical pathways. These species represent key components in the formation mechanism of chlorinated polyaromatic hydrocarbons. Results presented herein should provide better understanding of the evolution of soot from combustion/pyrolysis of short chlorinated alkenes.

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“…Surface adsorption studies, as well as studies of kinetics and thermochemistry, have been performed extensively using DFT. DFT has its strength in its accuracy and costs compared to other ab initio methods 71,72 . Time and length scales for DFT are in the order of 1 ps to 1 ns and 1 Å to a few nm respectively 73 .…”

Section: Present Status Of Sic-cvd Process Modelingmentioning

confidence: 99%

A Quantum Chemical Exploration of SiC Chemical Vapor Deposition

Sukkaew¹

2017

Linköping Studies in Science and Technology. Dissertations

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SiC is a wide bandgap semiconductor with many attractive properties. It has attracted particular attentions in the areas of power and sensor devices as well as biomedical and biosensor applications. This is owing to its properties such as large bandgap, high breakdown electric field, high thermal conductivities and chemically robustness. Typically, SiC homoepitaxial layers are grown using the chemical vapor deposition (CVD) technique. Experimental studies of SiC CVD have been limited to post-process measuring of the layer rather than in situ measurements. In most cases, the observations are presented in terms of input conditions rather than in terms of the unknown growth condition near the surface. This makes it difficult to really understand the underlying mechanism of what causes the features observed experimentally. With help of computational methods such as computational fluid dynamic (CFD) we can now explore various variables that are usually not possible to measure. CFD modeling of SiC CVD, however, requires inputs such as thermochemical properties and chemical reactions, which in many cases are not known. In this thesis, we use quantum chemical calculations to provide the missing details complementary to CFD modeling.We first determine the thermochemical properties of the halides and halohydrides of Si and C species, SiHnXm and CHnXm, for X being F, Cl and Br which were shown to be reliable compared to the available experimental and/or theoretical data. In the study of gas-phase kinetics, we combine ab initio methods and DFTs with conventional transition state theory to derive kinetic parameters for gas phase reactions related to Si-H-X species. Lastly, we study surface adsorptions related to SiC-CVD such as adsorptions of small C-H and Si-H-X species, and in the case of C-H adsorption, the study was extended to include subsequent surface reactions where stable surface products may be formed. iv SammanfattningSiC är ett halvledarmaterial med stort bandgap som har många attraktiva egenskaper. Det har fått särskilt mycket uppmärksamhet inom kraftkomponenter och sensorer, men också för tillämpningar inom biomedicin och biosensorer. Detta beror på materialets stora bandgap, förmågan att klara höga elektriska fält, goda värmeledningsförmåga och kemiska stabilitet. Epitaxiska skikt av SiC för kommersiella tillämpningar tillverkas med hjälp av kemisk ångdepo-sition (Chemical Vapor Deposition, CVD). Experimentella studier av SiC CVD begränsas till mätningar som görs i efterhand, snarare än under processens gång. För det mesta görs observationer med utgångspunkt från processens ingångsvärden istället för från de okända tillväxtförhållandena vid ytan. Detta gör det svårt att verkligen förstå de underliggande mekanismerna för de observerade experimentella resultaten. Med hjälp av beräkningsmetoder, såsom computational fluid dynamics (CFD) kan vi utforska olika variabler som vanligtvis inte går att mäta. Dock kräver CFD-modellering av SiC CVD ingångs-data i form av termokemiska egenskaper och kemiska reaktion...

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How Well Can Hybrid Density Functional Methods Predict Transition State Geometries and Barrier Heights?

Cited by 575 publications

References 36 publications

High-Level ab Initio Studies of Hydrogen Abstraction from Prototype Hydrocarbon Systems

High-Level ab Initio Studies of Hydrogen Abstraction from Prototype Hydrocarbon Systems

Formation of chlorobenzenes by oxidative thermal decomposition of 1,3-dichloropropene

A Quantum Chemical Exploration of SiC Chemical Vapor Deposition

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