Polishing the Gold Standard: The Role of Orbital Choice in CCSD(T) Vibrational Frequency Prediction

Bertels, Luke W.; Head‐Gordon, Martin

doi:10.1021/acs.jctc.0c00746

Cited by 31 publications

(46 citation statements)

References 97 publications

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“…As a final test of the quality of the results, we also compare with higher level theory calculations based on CCSD(T), which is often regarded as the gold standard of chemical accuracy in quantum chemistry. 87 Taking the same basis sets, we find that the T-CDFT results agree reasonably well with CCSD(T), 88,89 with a MAD of 0.5 eV for PBE S 1 energies. This is comparable to MADs for S 1 of 0.4 and 0.5 eV for PBE0 calculations with ∆SCF and TDDFT respectively, and lower than the PBE-based ∆SCF and TDDFT MADs of 1.0 and 0.8 eV respectively, further confirming the reliability of T-CDFT.…”

Section: Acenessupporting

confidence: 56%

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

Stella¹,

Kritam²,

Genovese³

et al. 2021

Preprint

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Despite the variety of available computational approaches, state-of-the-art methods for calculating excitation energies such as time-dependent density functional theory (TDDFT), are typically computationally demanding and thus limited to moderate system sizes. Here, we introduce a new variation of constrained DFT (CDFT), implemented in the wavelet-based BigDFT code, wherein the constraint corresponds to a particular transition (T) between occupied and virtual orbitals, rather than a region of the simulation space as in traditional CDFT. In this work, we perform benchmark T-CDFT calculations for a set of gas phase acene molecules and OLED emitters and compare them to ∆SCF and TDDFT results, for different functionals and basis sets. For both classes of molecules, we find that T-CDFT based on semi-local functionals is comparable to hybrid functional results from ∆SCF and TDDFT. Furthermore, T-CDFT proves to be more robust than ∆SCF and does not suffer from the well-known problems encountered when applying TDDFT to charge-transfer (CT) states, and is therefore equally applicable to both local excitations and CT states. Finally, since T-CDFT is designed for large systems and has been implemented in linear-scaling BigDFT, it is ideally suited for exploring the effects of explicit environments on excitation energies, paving the way for future simulations of excited states in complex realistic morphologies, such as those which occur in OLED materials.

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Section: Acenessupporting

confidence: 56%

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

Stella¹,

Kritam²,

Genovese³

et al. 2021

Preprint

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“…It is our expectation that when orbitals obtained from theories which include (even approximately) dynamical correlation such as DFT and κ-UOOMP2 are employed, subsequent CC predictions will improve in accuracy, as has already been seen in main group molecules. 145,146 Thus, in our view, the common notion that transition metals are difficult for traditional electronic structure methods is due to both static and dynamic correlation, yet we stress our finding that truly MR situations are encountered only in the special cases enumerated above (and perhaps a few others), making the proper treatment of dynamic correlation more important in most commonly-encountered cases.…”

Section: Metal Complexes With Higher Coordination Numbermentioning

confidence: 70%

Revealing the nature of electron correlation in transition metal complexes with symmetry breaking and chemical intuition

Shee

Loipersberger

Hait

et al. 2021

The Journal of Chemical Physics

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The present work provides a useful framework through which theoreticians and practicing computational chemists alike can view electron correlations in transition metal complexes. We present static correlation from the perspective of simple chemical models such as ligand-field and molecular orbital theories, and an analysis of symmetry breaking suggests that it is rarely encountered in thermochemical calculations of realistic transition metal compounds (though we do reveal a few important situations in which it is relevant). The relative complexity of transition metal bonding, relative to that of typical organic compounds, places a larger burden on a theory's treatment of dynamic correlation. After recognizing that simultaneous sigma-donation and pi-backbonding can be viewed as a correlated interaction involving multiple electron pairs, we demonstrate that MP2 and related double hybrid density functionals fail to describe this type of bonding. File list (2) download file view on ChemRxiv Correlation_in_Metal_Complexes_MS.pdf (773.44 KiB) download file view on ChemRxiv Correlation_in_Metal_Complexes_SI.pdf (123.19 KiB)

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“…We first consider the acenes, comparing our benchmark results with higher-level theory calculations based on CCSD(T), which is often regarded as the gold standard of chemical accuracy in quantum chemistry. 81 We employ the values from ref ( 82 ) (and references within). The low-lying singlet excitations in the acenes are termed 1 L a and 1 L b , which differ in energetic ordering depending on the acene in question.…”

Section: Resultsmentioning

confidence: 99%

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

Stella

Kritam

Genovese

et al. 2022

J. Chem. Theory Comput.

View full text Add to dashboard Cite

Despite the variety of available computational approaches, state-of-the-art methods for calculating excitation energies, such as time-dependent density functional theory (TDDFT), are computationally demanding and thus limited to moderate system sizes. Here, we introduce a new variation of constrained DFT (CDFT), wherein the constraint corresponds to a particular transition (T), or a combination of transitions, between occupied and virtual orbitals, rather than a region of the simulation space as in traditional CDFT. We compare T-CDFT with TDDFT and ΔSCF results for the low-lying excited states (S 1 and T 1 ) of a set of gas-phase acene molecules and OLED emitters and with reference results from the literature. At the PBE level of theory, T-CDFT outperforms ΔSCF for both classes of molecules, while also proving to be more robust. For the local excitations seen in the acenes, T-CDFT and TDDFT perform equally well. For the charge transfer (CT)-like excitations seen in the OLED molecules, T-CDFT also performs well, in contrast to the severe energy underestimation seen with TDDFT. In other words, T-CDFT is equally applicable to both local excitations and CT states, providing more reliable excitation energies at a much lower computational cost than TDDFT cost. T-CDFT is designed for large systems and has been implemented in the linear-scaling BigDFT code. It is therefore ideally suited for exploring the effects of explicit environments on excitation energies, paving the way for future simulations of excited states in complex realistic morphologies, such as those which occur in OLED materials.

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Polishing the Gold Standard: The Role of Orbital Choice in CCSD(T) Vibrational Frequency Prediction

Cited by 31 publications

References 97 publications

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

Revealing the nature of electron correlation in transition metal complexes with symmetry breaking and chemical intuition

Transition-Based Constrained DFT for the Robust and Reliable Treatment of Excitations in Supramolecular Systems

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