Effective basis set extrapolations for CCSDT, CCSDT(Q), and CCSDTQ correlation energies

Karton, Amir

doi:10.1063/5.0011674

Cited by 14 publications

(13 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The first of these is ΔT obtained as E CCSDT – E CCSD(T) calculated with the cc-pVDZ-PP and cc-pVTZ-PP basis sets and extrapolated to CBS with E L = E CBS + A L –3 . We refer readers to a recent study into the extrapolation of post-CCSD(T) energies for further insights, which also shows the mild dependence of the CBS energy on the extrapolation scheme A component for post-CCSDT correlation at the CCSDT(Q) level [Δ(Q)] is obtained as E CCSDT(Q) – E CCSDT calculated with the cc-pVDZ-PP basis set for Pd and cc-pVDZ for other elements.…”

Section: Resultsmentioning

confidence: 99%

DAPD Set of Pd-Containing Diatomic Molecules: Accurate Molecular Properties and the Great Lengths to Obtain Them

Chan

2023

J. Chem. Theory Comput.

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 99%

DAPD Set of Pd-Containing Diatomic Molecules: Accurate Molecular Properties and the Great Lengths to Obtain Them

Chan

2023

J. Chem. Theory Comput.

View full text Add to dashboard Cite

“…[38] (For a recent, more detailed discussion of basis set convergence of higher excitation terms, see Karton. [60,61] ) This phenomenon can be exploited in composite wavefunction-based thermochemistry approaches, as it is in our own W4 theory, [37,38] in the HEAT approach of Stanton and coworkers, [62][63][64][65] and in the FPD approach. [66,67] While a full discussion of basis set convergence would require a separate paper, suffice to say that unlike type A static correlation, the dynamical correlation energy converges very slowly with the basis set, roughly as ∝ N À 1 ; [68,69] if basis sets are built up of complete shells, such as the correlation consistent [70,71] cc-pVkZ family, then the number of basis functions in them grows cubically with the cardinal number k, and one recovers the familiar ∝ k À 3 inverse-cubic formula, [72] originally rationalized by the partial-wave expansion of atomic pair correlation energies.…”

Section: Dynamical and Static Correlationmentioning

confidence: 87%

Electron Correlation: Nature's Weird and Wonderful Chemical Glue

Martin

2021

Israel Journal of Chemistry

View full text Add to dashboard Cite

It can be argued that electron correlation, as a concept, deserves the same prominence in general chemistry as molecular orbital theory. We show how it acts as Nature's "chemical glue" at both the molecular and supramolecular levels. Electron correlation can be presented in a general chemistry course in an at least somewhat intuitive manner. We also propose a simple classification of correlation effects based on their length scales and the size of the orbital gap (relative to the two-electron integrals). In the discussion, we also show how DFT can shed light on wavefunction theory, and conversely. We discuss two types of "honorary valence orbitals", one related to small core-valence gaps, the other to the ability of empty 3d orbitals in 2 nd row elements to act as backbonding acceptors. Finally, we show why the pursuit of absolute total energies for their own sake becomes a sterile exercise, and why atomization energies are a more realistic "fix point".

show abstract

“…Results collected in Table S10 illustrate the approximate nature of CBS extrapolations that are based on small basis set results and standard extrapolation procedures (β = 3) . Differences Δ [(Q)‑(T)] → = [(Q)-(T)]/-[(Q)-(T)]/ 3̅ reach and even exceed 0.1 kcal/mol in a few cases and so need to be taken into account.…”

Section: Atomic-2: Model Developmentmentioning

confidence: 90%

Section: Lists the Final Cbs Estimates Of Ccsd(t) Atomization Energie...mentioning

confidence: 99%

ATOMIC-2 Protocol for Thermochemistry

Bakowies

2022

J. Chem. Theory Comput.

View full text Add to dashboard Cite

ATOMIC is a midlevel thermochemistry protocol that uses Pople's concept of bond separation reactions (BSRs) as a theoretical framework to reduce computational demands in the evaluation of atomization energies and enthalpies of formation. Various composite models are available that approximate bond separation energies at the complete-basis-set limit of all-electron CCSD(T), each balancing computational cost with achievable accuracy. Evaluated energies are then combined with very highlevel, precomputed atomization energies of all auxiliary molecules appearing in the BSR to obtain the atomization energy of the molecule under study. ATOMIC-2 is a new version of the protocol that retains the overall concept and all previously defined composite models but improves on ATOMIC-1 in various other ways: Geometry optimization and zero-point-energy evaluation are performed at the density functional level (PBE0-D3/6-311G(d)), which shows significant computational savings and better accuracy than the previously employed RI-MP2/cc-pVTZ. The BSR framework is improved, using more accurate complete-basis-set (CBS) extrapolations toward the Full CI limit for the atomization energies of all auxiliary molecules. Finally, and most importantly, an error and uncertainty model termed ATOMIC-2 um is added that estimates average bias and uncertainty for each of the atomization energy contributions that arise from the simplified treatment of some contributions to bond separation energies (CCSD(T)) and the neglect of others (such as higher order, scalar relativistic, or diagonal Born−Oppenheimer corrections) or from residual error in the energies of auxiliary molecules. Large and diverse benchmarks including up to 1179 molecules are used to evaluate necessary reference data and to correlate the observed error for each of the contributions with appropriate proxies that are available without additional quantum-chemical calculations for a particular molecule and represent its size and type. The implementation of ATOMIC-2 considers neutral, closed-shell molecules containing H, C, N, O, and F atoms; compared to ATOMIC-1, the framework has been extended to cover a few challenging but rare bond topologies. In comparison to highly accurate reference data for 184 molecules taken from the ATcT database (V. 1.122r), regular ATOMIC-2 shows noticeable underbinding, but the bias-corrected protocol ATOMIC-2 um is found to be more accurate than either ATOMIC-1 or standard Gaussian-4 theory, and the uncertainty model is consistent with statistics of actually observed errors. Problems arising from ambiguous or challenging Lewis-valence structures defining BSRs are discussed, and computational efficiency is demonstrated. Computer code is made available to perform ATOMIC-2 um analyses.

show abstract

Effective basis set extrapolations for CCSDT, CCSDT(Q), and CCSDTQ correlation energies

Cited by 14 publications

References 67 publications

DAPD Set of Pd-Containing Diatomic Molecules: Accurate Molecular Properties and the Great Lengths to Obtain Them

DAPD Set of Pd-Containing Diatomic Molecules: Accurate Molecular Properties and the Great Lengths to Obtain Them

Electron Correlation: Nature's Weird and Wonderful Chemical Glue

ATOMIC-2 Protocol for Thermochemistry

Contact Info

Product

Resources

About