Entropy Contributions to Transition State Modeling

Wispelaere, Kristof De; Vanduyfhuys, Louis; Speybroeck, Véronique Van

doi:10.1016/b978-0-12-805057-6.00006-5

Cited by 7 publications

(8 citation statements)

References 146 publications

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“…288 As the frequency of the vibrational mode tends to zero, the entropy tends to that of the free rotor, whereas as the vibrational mode tends to infinity, the entropy tends to that of the harmonic oscillator. While these methods achieve the aim of avoiding the spuriously high entropies 286 arising from artificially low frequencies, they have little physical motivation behind them.…”

Section: First-principles-based Mean-field Microkinetic Modelingmentioning

confidence: 99%

“…For adsorbates that are weakly binding, solvated systems, or systems at high temperatures, however, the harmonic oscillator approximation breaks down and anharmonic effects start to play a large role. , Campbell and Sellers developed a new method for measuring the entropies of weakly adsorbed molecular species such as methanol and alkanes. They find that the entropies of these molecules are much larger than that predicted from the harmonic oscillator approximation and that they can be readily estimated from the gas-phase entropy, an easily obtainable quantity, of the molecules (eq ): where S ads o ( T ) is the standard entropy of the adsorbate at temperature T , S gas o ( T ) is the standard gas phase entropy, and R is the molar gas constant.…”

Section: First-principles-based Microkinetic Modeling For Heterogeneo...mentioning

confidence: 99%

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Computational Methods in Heterogeneous Catalysis

2020

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The unprecedented ability of computations to probe atomic-level details of catalytic systems holds immense promise for the fundamentals-based bottom-up design of novel heterogeneous catalysts, which are at the heart of the chemical and energy sectors of industry. Here, we critically analyze recent advances in computational heterogeneous catalysis. First, we will survey the progress in electronic structure methods and atomistic catalyst models employed, which have enabled the catalysis community to build increasingly intricate, realistic, and accurate models of the active sites of supported transition-metal catalysts. We then review developments in microkinetic modeling, specifically mean-field microkinetic models and kinetic Monte Carlo simulations, which bridge the gap between nanoscale computational insights and macroscale experimental kinetics data with increasing fidelity. We finally review the advancements in theoretical methods for accelerating catalyst design and discovery. Throughout the review, we provide ample examples of applications, discuss remaining challenges, and provide our outlook for the near future.

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Section: First-principles-based Mean-field Microkinetic Modelingmentioning

confidence: 99%

Section: First-principles-based Microkinetic Modeling For Heterogeneo...mentioning

confidence: 99%

Computational Methods in Heterogeneous Catalysis

2020

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“…The interested reader is directed to Ref. [163,164], which discuss the challenges associated with the accurate prediction of entropies of activation. Some promising advances have been made in this area.…”

Section: Model Detailsmentioning

confidence: 99%

Impact of long-range electrostatic and dispersive interactions on theoretical predictions of adsorption and catalysis in zeolites

et al. 2018

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In this paper, we review the importance of long-range zeolite framework interactions in theoretical predictions for a variety of zeolite-catalyzed processes, and we show why such interactions must be determined accurately in order to reproduce experimentally measured adsorption and activation energies. We begin with an overview of the different strategies that have been used to account for long-range coulombic and dispersive interactions of zeolite framework atoms with species adsorbed at an active site. These methods include full periodic-DFT calculations and multi-layer hybrid techniques. Electrostatic interactions are observed to have a more significant impact than dispersive interactions on the geometries of ion-pair transition states and adsorbed species. Stabilization of the TS relative to reactant complexes is also dictated by electrostatic interactions. Dispersion effects are found to significantly stabilize both transition and reactant states for adsorbed species, especially those which have dimensions that provide good fits within the zeolite pore or cavity. We also show that the relevance of particular active site configurations can be missed, if the effects of long-range interactions are neglected. As a case in point, we demonstrate that a site previously considered inactive for ethane dehydrogenation, [GaH 2 ] + may in fact be more active than previously thought, when the impact of long-range interactions on the predicted activation energy is taken into account. Finally, the use of hybrid quantum mechanics/molecular mechanics approaches on extended, finite zeolite clusters has emerged as an accurate, highly cost-effective, and versatile alternative towards overcoming some of the present-day limitations of periodic calculations.

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“…We simulated ethene oligomerization in Ni-SSZ-24 using density-functional-theory-based molecular dynamics (DFT-MD) simulations and advanced free-energy sampling techniques. Such an approach has proven to account for the complexity of catalytic reactions at operating conditions by allowing for dynamic active sites and the influence of surrounding molecules. , The latter was found to be critical to investigate the nature of the active site in the presence of multiple ethene molecules. The computational results show a remarkable resemblance between the active sites in Ni-zeolites and homogeneous catalysts for alkene oligomerization, as ethene molecules reversibly mobilize the Ni site inside the zeolite pores.…”

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confidence: 99%

Ethene Dimerization on Zeolite-Hosted Ni Ions: Reversible Mobilization of the Active Site

et al. 2019

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The active site in ethene oligomerization catalyzed by Ni-zeolites is proposed to be a mobile Ni(II) complex, based on density functional theory-based molecular dynamics (DFT-MD) simulations corroborated by continuous-flow experiments on Ni-SSZ-24 zeolite. The results of the simulations at operating conditions show that ethene molecules reversibly mobilize the active site as they exchange with the zeolite as ligands on Ni during reaction. Microkinetic modeling was conducted on the basis of free-energy profiles derived with DFT-MD for oligomerization on these mobile [(ethene)2-Ni-alkyl]+ species. The model reproduces the experimentally observed high selectivity to dimerization and indicates that the mechanism is consistent with the observed second-order rate dependence on ethene pressure.

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Entropy Contributions to Transition State Modeling

Cited by 7 publications

References 146 publications

Computational Methods in Heterogeneous Catalysis

Computational Methods in Heterogeneous Catalysis

Impact of long-range electrostatic and dispersive interactions on theoretical predictions of adsorption and catalysis in zeolites

Ethene Dimerization on Zeolite-Hosted Ni Ions: Reversible Mobilization of the Active Site

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