Green's Function Coupled-Cluster Approach: Simulating Photoelectron Spectra for Realistic Molecular Systems

Area of Science:

• Quantum chemistry
• Computational physics
• Spectroscopy

Background:

• Accurate computation of molecular spectral functions is crucial for understanding electronic structure.
• Many-body effects significantly impact ionization processes, especially in core-level and inner valence regions.
• Existing methods may struggle to capture these complex many-body interactions efficiently.

Purpose of the Study:

• To present an efficient and scalable implementation of the analytical energy-dependent Green's function coupled-cluster with singles and doubles (GFCCSD) method.
• To demonstrate the capability of the GFCCSD approach in computing spectral functions for realistic molecular systems across various energy regions.
• To validate the accuracy of the GFCCSD method by comparing its results with experimental data and other theoretical approaches.

Main Methods:

• Development of an efficient, algebraically structured implementation of the energy-dependent Green's function coupled-cluster with singles and doubles (GFCCSD) method.
• Application of the GFCCSD method to compute spectral functions of realistic molecular systems.
• Comparison of computed spectral functions with experimental photoelectron spectra and other theoretical ionization potentials.

Main Results:

• The GFCCSD method demonstrates high scalability and capability to compute spectral functions in both valence and core-level energy regions.
• Observed satellite peaks in inner valence and core-level spectra highlight the significance of many-body effects beyond the single-particle picture.
• The GFCCSD method provides a qualitative to semiquantitative description of ionization processes.

Conclusions:

• The developed GFCCSD implementation is efficient and accurate for computing molecular spectral functions.
• The method successfully captures complex many-body effects, including satellite peaks, in ionization spectra.
• Improving results for main ionic states can be achieved with larger basis sets, while satellite states require higher-order many-body terms in the GFCC framework.