Toward Accurate Quantum Mechanical Thermochemistry: (2) Optimal Methods for Enthalpy Calculations from Comprehensive Benchmarks of 284 Model Chemistries

The Journal of Physical Chemistry A, Journal Year: 2025, Volume and Issue: unknown

Published: April 20, 2025

Accurate and efficient computations of the standard enthalpies formation (ΔHf°) for small organic molecules are crucial diverse chemical engineering scientific applications. Building on part 1 this work [J. Phys. Chem. A 2024, 128, 21, 4335-4352], we systematically benchmark 284 model chemistries ΔHf° computations. These methods span semiempirical approaches, density functional theory (DFT), wave function theory, composite schemes. We derive Petersson- Melius-type bond-additivity corrections (BACs) each method using a curated database 421 reference species. further validate top-performing an independent test set 500 species, including ions, radicals, other challenging cases. Across nearly all BACs significantly improve accuracy, especially neutral singlet Composite schemes coupling moderate-level DFT geometries with local coupled-cluster single-point energies strike excellent balance between cost often approaching accuracy (≤1 kcal/mol). Notably, DLPNO-CCSD(T)-F12d/cc-pVTZ-F12//ωB97X-D/def2-TZVPD Petersson BAC attains benchmark-best mean absolute error (MAE) 0.57 kcal/mol. Switching to DLPNO-CCSD(T)-F12d/cc-pVDZ-F12//GFN2-xTB reduces computational by order magnitude, only modest increase in MAE (0.96 Although carefully tuned can also benefit charged open-shell scarcity robust data these areas highlights need broader, high-accuracy thermochemistry datasets. Overall, provides practical guidance selecting optimal efficiently compute accurate under varied constraints molecular complexities, laying foundation large-scale, high-throughput thermochemical calculations that will support data-driven discovery industrial

Language: Английский

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Unifying thermochemistry concepts in computational heterogeneous catalysis

Chemical Society Reviews, Journal Year: 2024, Volume and Issue: unknown

Published: Nov. 29, 2024

Thermophysical properties of adsorbates and gas-phase species define the free energy landscape heterogeneously catalyzed processes are pivotal for an atomistic understanding catalyst performance.

Language: Английский

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Perspective on automated predictive kinetics using estimates derived from large datasets

International Journal of Chemical Kinetics, Journal Year: 2024, Volume and Issue: unknown

Published: June 25, 2024

Abstract A longstanding project of the chemical kinetics community is to predict reaction rates and behavior reacting systems, even for systems where there are no experimental data. Many important (atmosphere, combustion, pyrolysis, partial oxidations) involve a large number reactions occurring simultaneously, intermediates that have never been observed, making this goal more challenging. Improvements in our ability compute rate coefficients other parameters accurately from first principles, improvements automated kinetic modeling software, partially overcome many challenges. Indeed, some cases quite complicated models constructed which predicted results independent experiments. However, process constructing models, deciding measure or ab initio, relies on accurate estimates (and indeed most numerical estimates.) Machine‐learned trained datasets can improve accuracy these estimates, allow better integration quantum chemistry The need continued development shared (perhaps open‐source) software databases, directions improvement, highlighted. As we model weaknesses traditional ways doing modeling, testing exposed, identifying several challenges future research by community.

Language: Английский

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Thermodynamic and Chemical Kinetic Parameters in Ammonia Oxidation: A Comparison of Recent Studies and Parameter Recommendations

Energy & Fuels, Journal Year: 2024, Volume and Issue: 38(22), P. 22482 - 22500

Published: Oct. 29, 2024

Ammonia is a promising energy storage vector for renewable hydrogen and could become an essential part of the future mix. To efficiently utilize ammonia as fuel, overcome its relatively low reactivity high tailpipe emissions, optimize ratio different additives, it crucial to develop accurate chemical kinetic predictive abilities this system. In study, we review compare thermo-kinetic parameters from 19 reaction mechanisms published in five-year period 2018–2023. This comparison reveals concerning inconsistency thermodynamic used many species H/N H/N/O subsets. One was even double-counted (having two distinct labels with similar sets reactions) six these recent mechanisms. Twelve reactions were identified which reported rate coefficient deviates by 3 orders magnitude or more at 1000 K among reviewed sources. Not all literature are trackable properly cited. modeling suffers "many-model" problem, significant parameter values studies. The present work highlights some concerns attempts advance current state NH3 oxidation suggesting coherent set justified other quantum chemistry calculations here. It recommended that studies will justify thermokinetic they use─especially deviations established values─make sources trackable, provide glossary structures suggested mechanism.

Language: Английский

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