Cumulant Green's function methods for molecules.

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Mechanics

Background:

• The cumulant expansion of the Green's function (GW + C) is an efficient beyond-GW method.
• It enhances satellite features in materials by including higher-order correlation effects.
• GW + C shows promise for handling multi-particle processes and improving theoretical accuracy.

Purpose of the Study:

• To assess the performance of the GW + C scheme on molecular systems.
• To evaluate its accuracy for outer-valence quasiparticle and satellite energies.
• To explore applications of GW + C beyond condensed matter physics.

Main Methods:

• Application of ab initio cumulant expansions on top of GW (GW + C).
• Utilizing full configuration interaction (FCI) estimates as benchmarks.
• Testing on a series of 10-electron molecular systems (Ne, HF, H2O, NH3, CH4).

Main Results:

• GW + C accurately reproduces satellite structures in molecular systems.
• The method demonstrates good agreement with FCI benchmarks for quasiparticle and satellite energies.
• This study validates GW + C for molecular electronic structure calculations.

Conclusions:

• The GW + C approach is a viable and accurate method for studying molecular electronic properties.
• It offers a computationally efficient alternative for incorporating electron correlation effects.
• Further applications of GW + C in molecular quantum chemistry are warranted.