First-Principles Investigation of the Early 3d Transition Metal Diatomic Chlorides and Their Ions, ScCl0,±, TiCl0,±, VCl0,±, and CrCl0,±

121

131

In the present study, we have gathered a collection (that we term TMC151) of accurate reference data for transition-metal reactions for the assessment of quantum chemistry methods. It comprises diatomic dissociation energies and reaction energies and barriers for prototypical transition-metal reactions. Our assessment of a diverse range of different types of DFT methods shows that the most accurate functionals include ωB97M-V, ωB97X-V, MN15, and B97M-rV. Notably, they have also been previously validated to be highly robust for main-group chemistry. Nevertheless, even these methods show substantially worse accuracies for transition metals than for main-group chemistry. For less accurate methods, there is not a good correlation between their accuracies for main-group and transition-metal chemistries. Thus, in the development of new DFT, it is important to assess the accuracies for both types of data. In this regard, we have formulated the TMC34 model for efficient assessment of the performance for transition metals, which complements our previously developed MG8 model for main-group chemistry. Together, they provide a cost-effective means for initial assessment of new methodologies.

Section: Resultsmentioning

confidence: 72%

Section: Journal Of Chemical Theory and Computationmentioning

confidence: 78%

Assessment of DFT Methods for Transition Metals with the TMC151 Compilation of Data Sets and Comparison with Accuracies for Main-Group Chemistry

Chan

Gill

Kimura

2019

121

131

“…The calculated bond distances and frequencies were extrapolated to the CBS level by extrapolating the individual energies from the seven-point fits at the Q5 level. For TiCl, VCl, and CrCl, Kardahakis and Mavrides provide a good overview of experimental and computational values of these chlorides . We first describe the agreement of our calculated values with the more reliable experimental values.…”

Section: Resultsmentioning

confidence: 83%

Prediction of Bond Dissociation Energies/Heats of Formation for Diatomic Transition Metal Compounds: CCSD(T) Works

Fang

Vasiliu

Peterson

et al. 2017

107

143

It was recently reported ( J. Chem. Theory Comput. 2015 , 11 , 2036 - 2052 ) that the coupled cluster singles and doubles with perturbative triples method, CCSD(T), should not be used as a benchmark tool for the prediction of dissociation energies (heats of formation) for the first row transition metal diatomics based on a comparison with the experimental thermodynamic values for a set of 20 diatomics. In the present work the bond dissociation energies as well as the heats of formation for those diatomics have been calculated by the Feller-Peterson-Dixon approach at the CCSD(T)/complete basis set (CBS) level of theory including scalar relativistic corrections and correlation of the outer shell of core electrons in addition to the valence electrons. Revised experimental values for the hydrides are presented that are based on new heterolytic R-H bond dissociation energies, which are needed for analysis of the mass spectrometry experiments. The agreement between the calculated bond dissociation energies and the revised experimental values of the hydrides is good. Good agreement of the calculated bond dissociation energies/heats of formation is also found for most of the chlorides, oxides, and sulfides given the experimental error bars from experiment and those of the transition metal atoms in the gas phase. Thus, reliable results can be achieved by the CCSD(T) method at the CBS limit. The use of PW91 orbitals for the CCSD(T) calculations improves the predictions for some compounds with large T diagnostics at the HF-CCSD(T) level. The optimized bond distances and calculated vibrational frequencies for the diatomics also agree well with the available experimental values.

“…Highly correlated methods put it at ∼448 kJ/mol. 69 MnH (having a 7 ∑ + state) provides another example that also explains why we put less emphasis on the experimentally reported uncertainties than others do 11 (although some of these, in all fairness, are adequately estimated, many are probably not). The experimental value from the CRC Handbook 34 is 251 kJ/mol.…”

Section: ■ Results and Discussionmentioning

confidence: 96%

“…Another experimental estimate puts it at ∼500 kJ/mol, which is, on the other hand, too large using a similar analysis as the above. Highly correlated methods put it at ∼448 kJ/mol …”

Section: Resultsmentioning

confidence: 99%

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

Moltved

Kepp

2018

132

Despite their vast importance to inorganic chemistry, materials science, and catalysis, the accuracy of modeling the formation or cleavage of metal-ligand (M-L) bonds depends greatly on the chosen functional and the type of bond in a way that is not systematically understood. In order to approach a state of high-accuracy DFT for rational prediction of chemistry and catalysis, such system-dependencies need to be resolved. We studied 30 different density functionals applied to a "balanced data set" of 60 experimental diatomic M-L bond energies; this data set has no bias toward any d configuration, metal, bond type, or ligand as all of these occur to the same extent, and we can therefore identify accuracy bottlenecks. We show that the performance of a functional is very dependent on data set choice, and we dissect these effects into system type. In addition to the use of balanced data sets, we also argue that the precision (rather than just accuracy) of a functional is of interest, measured by standard deviations of the errors. There are distinct system dependencies both in the ligand and metal series: Hydrides are best described by a very large HF exchange percentage, possibly due to self-interaction error, whereas halides are best described by very small (0-10%) HF exchange fractions, and double-bond enforcing oxides and sulfides favor 10-25% HF exchange, as is also average for the full data set. Thus, average HF requirements hide major system-dependent requirements. For late transition metals Co-Zn, HF percentage of 0-10% is favored, whereas for the early transition metals Sc-Fe hybrid functionals with 20% HF exchange or higher are commonly favored. Accordingly, B3LYP is an excellent choice for early d-block but a poor choice for late transition metals. We conclude that DFT intrinsically underestimates the bond strengths of late vs early transition metals, correlating with increased effective nuclear charge. Thus, the revised RPBE, which reduces the overbinding tendency of PBE, is mainly an advantage for the early and mid transition metals and not very much for the late transition metals, i.e. there is a metal-dependent effect of the relative performance of RPBE vs PBE, which are widely used to study adsorption energetics on metal surfaces. Overall, the best performing functionals are PW6B95, the MN15 and MN15-L functionals, and the double hybrid B2PLYP.