Self-interaction corrected density functional calculations of molecular Rydberg states

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Physics

Background:

• Rydberg excited states are crucial for understanding molecular electronic properties.
• Accurate calculation of these states is computationally challenging.
• Existing methods often rely on basis sets that can be problematic for diffuse orbitals.

Purpose of the Study:

• To develop and present a novel computational method for calculating molecular Rydberg state wave functions and energies.
• To assess the accuracy and efficiency of the proposed method for various molecules.
• To enable accurate calculations of Rydberg electron binding energies in larger molecular systems.

Main Methods:

• Utilizes ground state density functional theory (DFT) with Perdew-Zunger self-interaction correction and an optimized effective potential for initial orbital estimation.
• Employs the Delta Self-Consistent Field (Delta-SCF) method to determine excited state energies by simulating electron excitation.
• Represents molecular orbitals on a real space grid, circumventing the need for specialized diffuse atomic basis sets.

Main Results:

• Successfully calculated wave functions and energies for several Rydberg states in molecules like NH3, H2O, H2CO, C2H4, and N(CH3)3.
• Achieved a mean absolute error of 0.18 eV across 33 molecular Rydberg states, demonstrating high accuracy.
• The real space grid approach shows favorable computational scaling (NM^2) and high parallelism, suitable for large molecules.

Conclusions:

• The presented DFT-based Delta-SCF method with real space grids provides an accurate and efficient approach for computing molecular Rydberg states.
• The method overcomes limitations associated with traditional basis set approaches.
• It offers a promising pathway for investigating Rydberg electron binding energies in complex and large molecular systems.