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A better multi-reference Davidson correction for internally contracted and uncontracted multi-reference configuration

David W Schwenke1

  • 1NASA Ames Research Center, Mail Stop 258-2, P.O. Box 1, Moffett Field, California 94035-0001, USA.

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|July 2, 2025
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Summary

A new multi-reference Davidson correction improves predictions of quadruple excitations in quantum chemistry. A hybrid approach combining this with conventional methods offers robust performance across various scenarios.

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Area of Science:

  • Quantum Chemistry
  • Computational Chemistry

Background:

  • Accurate prediction of electron correlation is crucial in quantum chemistry.
  • Existing correction methods have limitations in capturing complex excitation effects.

Purpose of the Study:

  • To develop a novel multi-reference Davidson correction for improved accuracy.
  • To evaluate the performance of the new correction, particularly for quadruple excitations.
  • To investigate a hybrid scheme for enhanced predictive power.

Main Methods:

  • Development of a new multi-reference Davidson correction.
  • Application of the correction to various chemical systems.
  • Comparison with existing correction methods.
  • Evaluation of a hybrid correction scheme averaging new and conventional approaches.

Main Results:

  • The new multi-reference Davidson correction significantly improves the prediction of quadruple excitation effects.
  • A hybrid correction scheme, averaging the new and a conventional correction, shows excellent performance.
  • The hybrid correction is effective even in challenging cases like avoided crossings of same-symmetry roots.

Conclusions:

  • The proposed multi-reference Davidson correction offers a substantial advancement in computational chemistry.
  • The hybrid correction scheme provides a reliable and accurate method for predicting electronic structure.
  • This work enhances the capability of theoretical methods to model complex molecular systems.