The INV24 test set: how well do quantum-chemical methods describe inversion and racemization barriers?

Abstract

For years, there has been ongoing interest in experimentally and theoretically understanding inversion and racemization processes. However, to the best of our knowledge, there has been no computational study that systematically investigated how well low-level quantum-chemical methods predict inversion barriers. Herein, we provide an answer to this question and we present the INV24 benchmark set of 24 high-level, ab initio inversion barriers. INV24 covers inversion in triatomics, in pyramidal molecules, in one cyclic system, and in various helical and bowl-shaped compounds. Our results indicate that previously applied DFT approximations combined with small basis sets are not reliable enough and that at least a triple-basis is needed for meaningful results. Moreover, we show that intramolecular London dispersion influences the barriers by 2 kcal/mol or more and that dispersion corrections should always be applied to DFT results. With our analysis of 34 DFT approximations, we can reproduce the well-known Jacob's Ladder scheme with (meta-)generalized-gradient-approximation methods underestimating barriers and global-hybrid DFT functionals performing better. Range-separated hybrids or Minnesota-type hybrids are not particularly superior to more conventional methods, such as B3LYP-D3. The by far best results are achieved with dispersioncorrected double hybrids, which give results below the chemical accuracy target of 1 kcal/mol. They also outperform wavefunction second-order perturbation theory approaches and we recommend using them whenever possible. Given that our systematic study of INV24 is the first of its kind, our findings have the potential to change common practice in this field and they will guide future investigations of inversion processes.Key words: barrier heights, chemical inversion, racemization barriers, benchmarking, density functional theory, wave-function theory.Résumé : Depuis des années, il y a un intérêt pour comprendre de manière expérimentale et théorique les processus d'inversion et de racémisation. Cependant, à notre connaissance, aucune étude computationnelle n'a évalué de manière systématique la précision des méthodes de chimie quantique de bas niveau pour prédire les barrières d'inversion. Dans le cadre des présents travaux, nous offrons une réponse à cette question et présentons la base de référence INV24 de 24 barrières d'inversion ab initio de haut niveau. L'application de la base INV24 couvre l'inversion des systèmes triatomiques dans les molécules pyramidales, dans un système cyclique et dans divers composés hélicoïdaux et de forme concave. Nos résultats indiquent que les approximations de DFT appliquées antérieurement, combinées avec des bases de petite taille, ne sont pas assez fiables et qu'une base tripleest minimalement requise pour que les résultats soient significatifs. De plus, nous montrons que la dispersion intramoléculaire de London a une incidence de 2 kcal/mol ou plus sur les barrières et que les résultats de DFT doivent toujours être corrigés pour tenir compte...

A look at the density functional theory zoo with the advanced GMTKN55 database for general main group thermochemistry, kinetics and noncovalent interactions

“…In 2016, Goerigk and Sharma presented the first comprehensive benchmark set for BHs in inversion and racemisation reactions (INV24). 84 It comprises 24 BHs for inversion in triatomic, pyramidal, cyclic, helical and bowl-shaped systems calculated at the W2-F12, W1-F12 or DLPNO-CCSD(T)/TightPNO/CBS(def2-TZVPP/def2-QZVPP) levels of theory ranging from 4.5 to 79.7 kcal mol À1 . The average barrier is 31.85 kcal mol À1 .…”

“…An exception to this rule are DFAs that contain a nonlocal vdW kernel, such as VV10 or oB97X-V. 153,155 Over the past years, it has been demonstrated that dispersion corrections also positively influence geometries of organic and biomolecular systems 44,[223][224][225][226][227][228] as well as the description of reaction energies and BHs. 50,84,222,229 This topic was also discussed for GMTKN30 in 2011. 7 These are only some of many examples in the literature, and yet, we still observe the common trend to rely on uncorrected DFAs in many computational organic chemistry applications; for a discussion on the shortcomings of such an approach, see e.g.…”

A Trip to the Density Functional Theory Zoo: Warnings and Recommendations for the User

“…In fact, it influences structural features of molecules and crystals, thermochemical properties, and reaction mechanisms. [40,68,74,[127][128][129][130][131][132][133][134][135] Bulky chemical groups can even serve as 'dispersion energy donors' [128] to overcome steric repulsion to form novel molecular structures. [127] When paired with a robust DFA, modern dispersion-corrected DFT has unprecedented accuracy and even outperforms some ab initio wave-function methods, as we demonstrated in our largest DFT benchmark study ever published.…”

Time-Dependent Double-Hybrid Density Functionals with Spin-Component and Spin-Opposite Scaling

“…[12][13][14] DHDFAs are currently regarded as the most sophisticated and most accurate DFAs for molecular thermochemistry, surpassing popular wave-function approaches, such as Møller-Plesset perturbation theory or even the composite complete-basis-set (CBS-QB3) approach. 8,[15][16][17][18][19] Due to its success for electronic ground states, the DHDFA approach has also been extended to the computation of electronic excitation energies. A first solution suggested by Grimme and Neese was to transfer the configuration interaction singles with perturbative doubles 20 (CIS(D)) approach to a time-dependent DFT (TD-DFT) formalism in 2007 (TD-DHDFAs).…”