Band structures in coupled-cluster singles-and-doubles Green's function (GFCCSD).

Area of Science:

• Quantum chemistry
• Materials science
• Computational physics

Background:

• Accurate calculation of electronic band structures and total energies is crucial for understanding material properties.
• Traditional theoretical methods often struggle to reproduce these properties, especially for complex systems.

Purpose of the Study:

• To demonstrate the efficacy of the coupled-cluster singles-and-doubles Green's function (GFCCSD) method for electronic structure calculations.
• To apply GFCCSD to various one-dimensional systems (LiH, C, Be chains) for the first time.
• To investigate the impact of electron correlation on bandgaps and the validity of active space approximations.

Main Methods:

• Application of the GFCCSD method to calculate single-electron energy spectra.
• Analysis of electronic band structures, including quasiparticle and satellite peaks.
• Investigation of computational cost reduction via active space restriction.

Main Results:

• GFCCSD successfully calculates electronic band structures and total energies for ionic, covalent, and van der Waals systems.
• Observed narrower bandgaps compared to Hartree-Fock (HF) due to electron correlation.
• Demonstrated that GFCCSD captures both quasiparticle and satellite peaks in band structures.
• Validated active space approximations for reduced computational cost with good agreement to full calculations.

Conclusions:

• GFCCSD is a powerful and accurate method for electronic structure calculations of periodic systems.
• The method provides explicit correlation, capturing essential electronic properties like bandgaps and spectral functions.
• Active space approximations can be employed to optimize GFCCSD computational efficiency without significant loss of accuracy.