A Unique QP Partitioning and Siegert Width Using Real-Valued Continuum-Remover Potential.

Area of Science:

• Quantum chemistry
• Theoretical chemistry
• Computational physics

Background:

• Autoionization resonances are crucial in understanding atomic and molecular electronic structures.
• Accurate computation of resonance energy and decay width remains a challenge in quantum chemistry.
• Existing methods often involve complex wave function partitioning.

Purpose of the Study:

• To develop a simple and practical quantum chemical procedure for computing autoionization resonance energy and decay width.
• To introduce the continuum-remover Feshbach projection operator (CR-FPO) formalism.
• To validate the CR-FPO formalism's accuracy and applicability.

Main Methods:

• Combines L^2-stabilized resonance wave functions with the continuum-remover (CR) potential and Feshbach projection operator (FPO) partitioning.
• Utilizes CR potential to confine the molecular system, removing the electronic continuum and localizing the resonance wave function.
• Employs a unique partitioning of the wave function into interaction and noninteraction regions based on level-shift criteria.

Main Results:

• The CR-FPO formalism provides accurate energy positions and decay widths for autoionization resonances.
• Demonstrated high accuracy for model Hamiltonians and doubly excited states of atomic/molecular systems at the full-CI level.
• Successfully applied to calculate the 2Π shape resonance in N2- using the multireference configuration interaction (MRCI) method.

Conclusions:

• The CR-FPO formalism offers a straightforward and accurate method for studying autoionization resonances.
• This approach simplifies complex quantum chemical calculations, making it highly practical.
• The CR-FPO method shows significant promise for advancing the understanding of resonance phenomena in various systems.