Multiconfigurational short-range density-functional theory for open-shell systems.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Many chemical systems require advanced quantum chemistry methods beyond single-reference wave functions.
• Accurate predictions necessitate balancing static and dynamic electron correlation.
• Existing methods like perturbation theory can be computationally expensive.

Purpose of the Study:

• To generalize the multiconfigurational short-range density-functional theory (MC-srDFT) method to open-shell chemical systems.
• To improve the efficiency and accuracy of computational chemistry for a wider range of molecules.
• To address limitations of current quantum chemistry approaches in describing complex electronic structures.

Main Methods:

• Development and implementation of a hybrid approach combining multiconfigurational wave functions and density-functional theory (DFT) with range separation.
• Derivation and incorporation of additional terms necessary for treating open-shell systems within the MC-srDFT framework.
• Utilized the DALTON quantum chemistry program for the implementation.

Main Results:

• Successfully generalized MC-srDFT to handle open-shell systems, expanding its applicability.
• The MC-srDFT method efficiently captures both static correlation (via MC) and dynamic correlation (via DFT approximations).
• Demonstrated the method's performance on challenging open-shell systems like dioxygen and the hexaaquairon(III) complex.

Conclusions:

• The generalized MC-srDFT provides a more efficient and accurate approach for studying open-shell chemical systems.
• This advancement overcomes previous restrictions to closed-shell systems, broadening the scope of MC-srDFT.
• The method offers a promising avenue for accurate energetic and spectroscopic property predictions in complex chemical environments.