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Time-Dependent Double-Hybrid Density Functionals with Spin-Component and Spin-Opposite Scaling.

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|August 2, 2017
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We introduce spin-component/spin-opposite scaling (SCS/SOS) for time-dependent double-hybrid density functional approximations (TD-DHDFAs) to accurately calculate electronic excitation energies. These enhanced TD-DHDFAs achieve high accuracy, comparable to costly wave function methods.

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Area of Science:

  • Computational Chemistry
  • Quantum Chemistry
  • Theoretical Chemistry

Background:

  • Accurate calculation of electronic excitation energies is crucial for understanding molecular properties and reactions.
  • Existing time-dependent double-hybrid density functional approximations (TD-DHDFAs) show promise but can exhibit outliers and performance variations.
  • Wave function methods, while accurate, are computationally expensive for large systems.

Purpose of the Study:

  • To combine TD-DHDFAs with spin-component/spin-opposite scaling (SCS/SOS) for improved electronic excitation energy calculations.
  • To evaluate the performance of various SCS/SOS-TD-DHDFAs against benchmark datasets and reference methods.
  • To introduce new CC3 reference data for the Gordon benchmark set.

Main Methods:

  • Implementation and testing of different SCS/SOS parameterizations for six parent TD-DHDFAs.
  • Cross-validation using three benchmark sets of small- to medium-sized chromophores.
  • Comparison of results with CC3 reference values and other wave function methods.

Main Results:

  • Unscaled TD-DHDFAs are already accurate and outperform some wave function methods.
  • SCS/SOS significantly reduces outliers and deviations (up to 0.5 eV) from reference values.
  • SCS/SOS methods align Tamm-Dancoff approximation (TDA) performance with full TD calculations and balance description of excitation types.
  • Best SCS/SOS-TD-DHDFAs achieve mean absolute deviations as low as 0.14 eV compared to CC3.
  • SOS variants show excellent performance, a notable advantage over wave function methods.

Conclusions:

  • SCS/SOS significantly enhances the accuracy and reliability of TD-DHDFAs for electronic excitation energies.
  • These improved methods offer a computationally efficient alternative to expensive wave function approaches.
  • The developed SCS/SOS-TD-DHDFAs are suitable for applications like excited-state geometry optimization, especially when combined with techniques like the Laplace transform.