BH9, a New Comprehensive Benchmark Data Set for Barrier Heights and Reaction Energies: Assessment of Density Functional Approximations and Basis Set Incompleteness Potentials

Abstract

The calculation of accurate reaction energies and barrier heights is essential in computational studies of reaction mechanisms and thermochemistry. To assess methods regarding their ability to predict these two properties, high-quality benchmark sets are required that comprise a reasonably large and diverse set of organic reactions. Due to the time-consuming nature of both locating transition states and computing accurate reference energies for reactions involving large molecules, previous benchmark sets have been limited in scope, the number of reactions considered, and the size of the reactant and product molecules. Recent advances in coupled-cluster theory, in particular local correlation methods like DLPNO-CCSD(T), now allow the calculation of reaction energies and barrier heights for relatively large systems. In this work, we present a comprehensive and diverse benchmark set of barrier heights and reaction energies based on DLPNO-CCSD(T)/CBS called BH9. BH9 comprises 449 chemical reactions belonging to nine types common in organic chemistry and biochemistry. We examine the accuracy of DLPNO-CCSD(T) vis-a-vis canonical CCSD(T) for a subset of BH9 and conclude that, although there is a penalty in using the DLPNO approximation, the reference data are accurate enough to serve as a benchmark for density functional theory (DFT) methods. We then present two applications of the BH9 set. First, we examine the performance of several density functional approximations commonly used in thermochemical and mechanistic studies. Second, we assess our basis set incompleteness potentials regarding their ability to mitigate basis set incompleteness errors. The number of data points, the diversity of the reactions considered, and the relatively large size of the reactant molecules make BH9 the most comprehensive thermochemical benchmark set to date and a useful tool for the development and assessment of computational methods.

Electrochemical PINOylation of Methylarenes: Improving the Scope and Utility of Benzylic Oxidation through Mediated Electrolysis

“…None of the variations in reaction conditions noted above significantly affected the C–O/C–N product ratio. Composite wavefunction and density functional theory (DFT) computational methods − were used to evaluate two possible pathways for the formation of 2a C–N and to compare their relative energetics to radical coupling to form 2a C–O (Figure ; see Section 4 of the Supporting Information for details). Path I involves a direct reaction of the benzyl radical with the oxygen atom of PINO to afford 2a C–O .…”

Small basis set density-functional theory methods corrected with atom-centered potentials

“…Water38 124 , Water1888 SSI-anionic c,108 , WatAA-anionic b,c,117 , HSGanionic c,78,118 , PLF547-anionic c,119 , IonicHB-anionic c,81 , IHB100x10-anionic c,82 , Ionic43-anionic c,134 191,192 , MOLdef-TS n,o, 74 16,582 -98.43 to +49.38 molecular deformation energies of various molecules deformed along their normal modes ISO34 14,193 , ISOL24 14,194 , IDISP 14,161,164,193,195,196 a) defined as the difference between the energy of the complex and the sum of the monomer energies. A negative interaction energy indicates the complex is more stable than the separated monomers.…”

“…This improvement originates mostly from the good performance of ACPs (MAE reductions by 13-52%) on the four main BH data sets: Grambow2020-B97D3 (32,722 data points), Grambow2020-ωB97XD3 (23,922 data points), BH9 (898), and E2SN2 (418). Note that the BH9 data set was designed recently 74 to be used for the particular purpose of developing the ACPs in this work and contains various model reactions that increase the diversity of the BH data in the training set.…”

“…Covalent properties such as reaction energies, barrier heights, and bond separation energies are mostly underestimated (positive MSEs) with a substantial error spread. In the particular case of barrier heights and the BLYP functional, this may be attributed to delocalization error 74 , which is partially remedied by the application of ACPs. For the covalent properties, application of the ACPs also decreases both the MSE and SDs substantially.…”

Benefits of Range-Separated Hybrid and Double-Hybrid Functionals for a Large and Diverse Data Set of Reaction Energies and Barrier Heights

“… 58 , 60 − 68 Hence, assessing quantum chemical methods on kinetic and thermochemical properties based on such databases is prone to bias. Aiming to solve this issue, DiLabio and co-workers 69 , 70 have recently proposed a large and sufficiently diverse benchmark set, BH9, composed of 449 reaction energies and 898 barrier heights (including forward and reverse). Their data set contains nine types of reactions: (i) radical rearrangement, (ii) Diels–Alder, (iii) halogen atom transfer, (iv) hydrogen atom transfer, (v) hydride transfer, (vi) B- and Si-containing reactions, (vii) proton transfer, (viii) nucleophilic substitution, and (ix) nucleophilic addition.…”