GW+2SOSEX Self-Energy Made Positive Semidefinite.

Area of Science:

• Quantum chemistry
• Condensed matter physics
• Computational materials science

Background:

• Vertex corrections beyond the GW approximation are challenging.
• Ensuring positive semidefiniteness of self-energies is crucial for theoretical rigor.
• Existing vertex-corrected approximations often lack this property.

Purpose of the Study:

• To develop a positive semidefinite extension of the GW+2SOSEX self-energy.
• To address the lack of positive semidefiniteness in common self-energy approximations.
• To improve the accuracy of quasiparticle energy predictions.

Main Methods:

• Formulation of a positive semidefinite extension named GW+2SOSEX-psd.
• Demonstration of the cancellation of bare energy poles in G3W2.
• Application to molecular systems to validate the method.

Main Results:

• The proposed GW+2SOSEX-psd approximation satisfies positive semidefiniteness.
• Accurate prediction of quasiparticle energies for valence and core states.
• Validation on molecular examples confirms the method's efficacy.

Conclusions:

• The GW+2SOSEX-psd method provides a theoretically sound and accurate approach.
• This work advances the development of reliable electronic structure calculations.
• The method shows promise for accurate predictions in quantum chemistry and condensed matter physics.