Influence of the complete basis set approximation, tight weighted‐core, and diffuse functions on the DLPNO‐CCSD(T1) atomization energies of neutral H,C,O‐compounds

Abstract

The impact of complete basis set extrapolation schemes (CBS), diffuse functions, and tight weighted‐core functions on enthalpies of formation predicted via the DLPNO‐CCSD(T1) reduced Feller‐Peterson‐Dixon approach has been examined for neutral H,C,O‐compounds. All tested three‐point (TZ/QZ/5Z) extrapolation schemes result in mean unsigned deviation (MUD) below 2 kJ mol−1 relative to the experiment. The two‐point QZ/5Z and TZ/QZ CBS 1/lmax3 extrapolation schemes are inferior to their inverse power counterpart (1/()lmax+1/24) by 1.3 and 4.3 kJ mol−1. The CBS extrapolated frozen core atomization energies are insensitive (within 1 kJ mol−1) to augmentation of the basis set with tight weighted core functions. The core‐valence correlation effects converge already at triple‐ζ, although double‐ζ/triple‐ζ CBS extrapolation performs better and is recommended. The effect of diffuse function augmentation converges slowly, and cannot be reproduced with double‐ ζ or triple‐ ζ calculations as these are plagued with basis set superposition and incompleteness errors.

Gas‐phase thermochemistry of noncovalent ligand–alkali metal ion clusters: An impact of low frequencies

“…The AutoAux code was used to generate the auxiliary correlation fitting /C basis sets 57 for the cc‐pwCV n Z basis sets. The CBS (DZ/TZ, Equation ) extrapolation was performed based on the individual E CV values calculated for reactants with the double‐ and triple‐ζ quality basis sets as suggested in our recent work 58 …”

“…The CBS (DZ/TZ, Equation 2) extrapolation was performed based on the individual E CV values calculated for reactants with the double-and triple-ζ quality basis sets as suggested in our recent work. 58 The ΔE IT term of Equation ( 1) is calculated as the difference between the DLPNO-CCSD(T1) and DLPNO-CCSD(T) reaction energies obtained with cc-p(wC)VTZ basis sets.…”

Ni, Cu, Zn, Pd, Ag and Cd Tetraphenylporphyrin Ab Initio Thermochemistry: Enthalpy of Formation of ZnTPP Revisited

“…Built on our previous experience, 27,57 the following variant of the composite Feller-Peterson-Dixon (FPD) method was used for the calculations of accurate reaction enthalpy changes:…”

“…68−70 Auxiliary correlation fitting basis sets (cc-pVnZ/C) developed by Weigend et al 71 were used on the nonmetal atoms, while for the metal atoms, these basis sets were automatically generated using the "AutoAux" keyword. 72 The calculated electronic energies of the MTPPs and reference species were extrapolated using the recently recommended 57,73 1/(l max + 1/2) 4 scheme of Martin. 74 The ΔE CV contribution was evaluated as the difference between the "all electron" (AE) and "frozen core" (FC) DLPNO−CCSD(T)/CBS reaction energies.…”

“…Built on our previous experience, , the following variant of the composite Feller-Peterson-Dixon (FPD) method was used for the calculations of accurate reaction enthalpy changes: where Δ E CBS is the complete basis set (CBS) extrapolated energy change, Δ E CV refers to the effect of the core–valence electron correlation on the reaction energy, Δ E PNO is the correction introduced by using Complete PNO Space (CPS) , extrapolated instead of the NormalPNO energies, Δ E IT is the effect due to the use of the T1 iterative triples instead of their semicanonical (T0) counterparts, and Δ H CORR is enthalpy correction. Below, we detail each of the separate contributions to the reaction enthalpies.…”