Troubles in the Systematic Prediction of Transition Metal Thermochemistry with Contemporary Out-of-the-Box Methods

Abstract

The recently developed DLPNO-CCSD(T) method and seven popular DFT functionals (B3LYP, M06, M06L, PBE, PBE0, TPSS, and TPSSh) with and without an empirical dispersion term have been tested to reproduce 111 gas phase reaction enthalpies involving 11 different transition metals. Our calculations, corrected for both relativistic effects and basis set incompleteness, indicate that most of the methods applied with default settings perform with acceptable accuracy on average. Nevertheless, our calculations also evidenced unexpected and nonsystematic large deviations for specific cases. For group 12 metals (Zn, Cd, Hg), most of the methods provided mean unsigned errors (MUE) less than 5.0 kcal/mol, with DLPNO-CCSD(T) and PBE methods performing excellently (MUE lower 2.0 kcal/mol). Problems started with group 4 metals (Ti and Zr). The best performer for Zr complexes with MUE of 1.8 kcal/mol, PBE0-D3, provides MUE larger than 8 kcal/mol for Ti. DLPNO-CCSD(T) provides a reasonable MUE of 3.3 kcal/mol for Ti reactions but gives MUE a larger than 14.4 kcal/mol for Zr complexes, with all the larger deviations for reactions involving ZrF4. Large and nonsystematic errors have been obtained for group 6 metals (Mo and W), for eight reactions containing Fe, Cu, Nb, and Re complexes. Finally, for the whole set of 111 reactions, the DLPNO-CCSD(T), B3LYP-D3, and PBE0-D3 methods turned out to be the best performers, all providing MUE below 5.0 kcal/mol. Since DFT results cannot be systematically improved and large nonsystematic deviations of 20-30 kcal/mol were obtained even for best performers, our results indicate that current DFT methods are still unable to provide robust predictions in transition metal thermochemistry, at least for the functionals explored in this work. The same conclusion holds for both DLPNO-CCSD(T) and canonical CCSD(T) methods when used entirely as out-of-the-box. However, if careful investigation of core correlation is performed, relativistic effects are properly included and the quality of the reference wave function is properly checked, CCSD(T) methods can still provide good quality results that might even be used to validate DFT methods due to paucity of accurate thermodynamic data for realistic-sized transition metal complexes.

Pair natural orbital and canonical coupled cluster reaction enthalpies involving light to heavy alkali and alkaline earth metals: the importance of sub-valence correlation

“…43 Subsequent studies indicated that the documented failure can be related to insufficiently large basis sets. 44,45 Indeed, we have recently shown that many reaction enthalpies involving transition metals were not affected by the frozen core approach 18,46 We do not exclude that in many cases the surprisingly good performance of the FC approach might result from the lucky cancellation of errors from neglecting core and core-valence correlation in both reactants and products. However, few reactions turned out to be very sensitive to the frozen core settings, leading to errors of 30-40 kcal mol À1 when the default FC settings were used, for example reactions of ZrF 4 with Cl 2 , Br 2 or I 2 .…”

Chemical Bond Energies of 3d Transition Metals Studied by Density Functional Theory

“…they represent a balanced data set for which the performance can be divided into system type. Previous similar studies [11][12][13][29][30][31] should be considered in this context. The main novelty of our study is the use of a balanced dataset studied with a wide range of Theory and Computation 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 6 modern density functionals of various design types.…”

Superhalogen and Superacid

“…[23] This method was shown to provide results of canonical coupled cluster quality. [24][25][26][27][28][29][30] All the calculations were performed for gas phase.…”

“…Thus, dodecahedrane cage seems to be the best fit for fluorine atom. Another try to improve the structure was changing cyano groups to CF 3 ones, but that quickly lead to 20 9.766 −11.768 F@C 24 (CN) 24 9.502 −11.482 F@C 28 (CN) 28 9.484 −11.455 overcrowding of fluorine atoms, preventing the proper delocalization of negative charge. Looking at carborane cages, we noticed that the cage CB 11 of C 5v symmetry, decorated with 12 CF 3 groups ( Fig.…”

“…F@D 6d -C 24 (CN)24 (left) and F@T d -C 28 (CN)28 (right). Color coding: C, cyan; N, dark blue; F, olive.…”