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On the performance of QTP functionals applied to second-order response properties.
Rodrigo A Mendes1, Zachary W Windom1, Hyunsik Kim1
1Quantum Theory Project, University of Florida, Gainesville, Florida 32611, USA.
Correlated orbital theory (COT) offers a simpler way to calculate electron correlation in molecular orbitals. This study finds specific Quantum Theory Project (QTP) exchange-correlation functionals accurately predict response properties like polarizability and NMR couplings.
Area of Science:
- Quantum chemistry
- Computational chemistry
- Theoretical chemistry
Background:
- Correlated orbital theory (COT) provides an exact one-particle treatment for electron correlation.
- Traditional correlated methods (e.g., EOM-CC) are computationally intensive.
- The Quantum Theory Project (QTP) developed exchange-correlation (XC) functionals to emulate COT.
Purpose of the Study:
- To evaluate the accuracy of QTP XC functionals for calculating molecular response properties.
- To compare the performance of orbital-specific COT calculations with established correlated methods.
- To identify optimal XC functionals for static polarizabilities, NMR coupling constants, and chemical shifts.
Main Methods:
- Comparison of orbital-specific calculations using 33 QTP XC functionals against EOM-CCSD results.
- Evaluation of static polarizabilities, nuclear magnetic resonance (NMR) coupling constants, and chemical shifts.
- Analysis of functional performance based on mean absolute deviation and percentage error.
Main Results:
- LC-QTP XC yielded the smallest mean absolute deviation (0.28 a.u.) for static polarizability.
- QTP01 demonstrated the best performance for total nuclear spin-spin coupling constants (%Error = 10.63%).
- TPSS0 excelled in chemical shift predictions, with TPSS0, ωB97X, QTP00, QTP01, and QTP02 recommended for overall chemical shift studies (R² = 0.96).
Conclusions:
- Orbital-specific COT calculations using QTP XC functionals accurately reproduce correlated EOM-CC results.
- This approach facilitates orbital-by-orbital interpretation of electron correlation effects.
- Selected QTP XC functionals are suitable for accurate and efficient computation of molecular response properties.

