Short-range density functional correlation within the restricted active space CI method

Area of Science:

• Computational chemistry
• Quantum chemistry
• Electronic structure theory

Background:

• Restricted active space configuration interaction (RASCI) method misses dynamic electron correlations.
• Accurate calculation of electron correlations is crucial for predicting molecular properties.

Purpose of the Study:

• To develop a hybrid wave function-density functional theory (DFT) method.
• To recover dynamic electron correlations absent in RASCI.
• To improve the computation of electronic ground and excited states.

Main Methods:

• Introduced a range-separated hybrid approach combining RASCI with DFT.
• Developed working equations and computational algorithms for the new RAS-srDFT method.
• Tested the method on excitation energy calculations for organic molecules.

Main Results:

• The RAS-srDFT method successfully recovers dynamic electron correlations.
• Calculations of relative energies showed quantitative improvement over standard RASCI.
• The combination of RASCI wave functions and short-range DFT functionals yielded promising results.

Conclusions:

• RAS-srDFT is a promising method for accurately computing electronic structures.
• The method offers a significant improvement for systems requiring accurate dynamic and nondynamic electron correlation.
• This work lays the foundation for advanced electronic structure calculations.