Scalable Correlated Local Approaches for Computing Valence and Core-Level Ionization Energies in Large Molecules.

Area of Science:

• Quantum Chemistry
• Computational Physics

Background:

• Calculating ionization energies is crucial for understanding molecular properties.
• Existing methods can be computationally expensive for large systems.

Purpose of the Study:

• Introduce a scalable framework for calculating valence and core ionization energies.
• Enable routine application of ADC(2) methods to large molecular systems.

Main Methods:

• Developed a state-specific orbital domain construction within the ADC(2) formalism.
• Implemented a black-box approach requiring no system-specific tuning.
• Tested on conventional ADC(2), spin-opposite-scaled ADC(2), and ADC(2)-based double-hybrid functional.

Main Results:

• Errors from local approximation are minimal compared to intrinsic method uncertainties.
• Deviations for valence and core ionization energies are typically hundredths of an electronvolt.
• Achieved substantial orbital space reduction, significantly accelerating computations.

Conclusions:

• The framework enables routine ADC(2) calculations for systems previously out of reach.
• Demonstrated efficiency for extended molecular systems, like TADF emitters and porphyrin derivatives.
• Valence ionization energy of a 132-atom system in ~20 min; 4 N K-edge energies of a 372-atom system in ~2 h.