SVECV‐f12: Benchmark of a composite scheme for accurate and cost effective evaluation of reaction barriers

Abstract

A simple composite scheme is presented and benchmarked against the 38 reactions in Truhlar's HTBH38/08 and NHTBH38/08 databases. Mean unsigned deviation (MUD) for the complete set of 68 independent barriers is 0.40 kcal mol À1 , compared to 1.31 kcal mol À1 for G4 and 1.62 kcal mol À1 for the M06-2X-D3 method. The MUD of the new scheme on the barriers in the DBH24/08 subset (12 out of the 38 reactions in the other sets) is 0.27 kcal mol À1 , better than that obtained at the expensive CCSD(T,full)/aug-cc-pCV(T+d)Z level (0.46 kcal mol À1 ) and comparable to the most exact (and costly) Wn calculations (MUD = 0.14 kcal mol À1 ). The method was further tested against a subset of reactions, for which the geometry and energies of all species were determined at the much more demanding CCSD(T)-F12//pVQZ-F12 level. The SVECV-f12 procedure on this database results in RMSE and MUD values of only 0.21 and 0.16 kcal mol À1 .

Degradation mechanism of 2-fluoropropene by Cl atoms: experimental and theoretical products distribution studies

“…Two ab initio post-Hartree–Fock composite methods were also employed in this work to estimate the energies of the species at essentially the CCSD(T)/CBS most accurate level. One of the methods was the G4 procedure of Curtiss et al 39 (which uses geometries optimized at the B3LYP level) and the SVECV-f12 method of Ventura et al 40 This last composite method uses the geometries optimized at the M06-2X-D3/aug-cc-pVTZ level and evaluates the energies using the explicitly correlated CCSD(T)-F12 41,42 method with the pVDZ-F12 43 and pVTZ-F12 43 basis sets used to extrapolate to the Complete Basis Set (CBS) limit. The RI approximation was applied using the OptRI auxiliary basis sets from ref.…”

“…46 Core valence correlation energies were also taken into account employing the cc-pVCTZ basis set, 47 which includes tight functions to better represent the core of the atoms, and the MP2 method, sufficiently accurate for this purpose, as shown in a previous publication. 40…”

Dipolar 1,3‐cycloaddition of thioformaldehydeS‐methylide (CH2SCH2) to ethylene and acetylene. A comparison with (valence) isoelectronicO3,SO2,CH2OOandCH2SO

“…In order to account for dispersion interactions, M06‐2X and rev‐DSDPBEP86 were augmented by Grimme's DFT‐D3 semiempirical dispersion, 62,63 which has been applied with considerable success to a large number of different systems, including dimers, large supramolecular complexes and reaction energies/barriers. The well‐documented CBS‐QB3, 64 G4, 65 and W1BD 66 composite methods were used in their original implementations, together with the more recent SVECV‐f12 67 and jun‐ChS 68,69 models. SVECV‐f12, in the implementation used in this paper, employs M06‐2X‐D3/jun‐cc‐pV(T+ d )Z optimum geometries to perform CCSD(T)‐F12b(3C/FIX) 70 complete basis set (CBS) single‐point calculations (obtained by extrapolation of cc‐pVDZ‐F12 and cc‐pVTZ‐F12 results), augmented by core‐valence correlation corrections at the MP2/cc‐pCVTZ level.…”

“…60,61 In order to account for dispersion interactions, M06-2X and rev-DSDPBEP86 were augmented by Grimme's DFT-D3 semiempirical dispersion, 62,63 which has been applied with considerable success to a large number of different systems, including dimers, large supramolecular complexes and reaction energies/barriers. The well-documented CBS-QB3, 64 G4, 65 and W1BD 66 composite methods were used in their original implementations, together with the more recent SVECV-f12 67 Z basis sets and as the difference between MP2/cc-pwCVTZ results…”

Experimental and Theoretical Kinetic Studies of the Ozonolysis of Selected Allyl Sulfides (H2C═CHCH2SR, R = CH3, CH3CH2): The Effect of Nascent OH Radicals

“…To obtain more accurate reaction barriers, the recently developed SVECV-f12 composite method was used . This method evaluates the energy using explicitly correlated CCSDS­(T)-F12 , with pVDZ-F12 and pVTZ-F12 basis sets to extrapolate to the complete basis set limit.…”