Electron-propagator methods versus experimental ionization energies.

Area of Science:

• Quantum Chemistry
• Computational Physics
• Spectroscopy

Background:

• Electron-propagator (EP) methods are crucial for calculating molecular vertical ionization energies.
• Comparing EP methods with experimental and high-level computational data is essential for assessing their accuracy and efficiency.

Purpose of the Study:

• To evaluate the accuracy and efficiency of various electron-propagator methods for molecular vertical ionization energies.
• To compare the performance of EP methods against established computational techniques and experimental standards.

Main Methods:

• Utilizing electron-propagator (EP) methods with varying computational scaling (cubic, O2V3, OV4).
• Employing composite EP models incorporating basis-set saturation effects.
• Generating Dyson orbitals using generalized self-energy matrices and non-iterative contractions.

Main Results:

• EP methods achieve high accuracy, with mean absolute errors (MAEs) below 0.2 eV for cubic scaling and around 0.1 eV for O2V3 scaling.
• OV4 methods demonstrate accuracy comparable to or exceeding ΔCCSD(T) at higher efficiency.
• Composite EP models enhance efficiency without compromising accuracy.

Conclusions:

• Electron-propagator methods provide a highly accurate and computationally efficient route to molecular vertical ionization energies.
• These methods offer a reliable alternative to traditional computational approaches, especially when Koopmans's theorem is applicable.
• The development of parameter-free EP methods advances the field of quantum chemical calculations.