Integral approximations in ab initio, electron propagator calculations.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Traditional ab initio calculations involve computationally expensive four-center integrals for interelectronic repulsion.
• Electron-propagator methods are crucial for describing electronic properties but can be limited by computational cost.

Purpose of the Study:

• To develop and validate a novel computational approach that avoids four-center integrals in ab initio electron-propagator calculations.
• To assess the impact of this new method on computational resource requirements and accuracy.

Main Methods:

• Incorporation of treatments for interelectronic repulsion that bypass four-center integrals.
• Application within ab initio electron-propagator frameworks using diagonal self-energy matrices.
• Regeneration of four-index electron-repulsion integrals from three-index intermediates.

Main Results:

• Substantial reduction in storage requirements for propagator calculations.
• Lowering the scaling of integral transformations to the molecular orbital base by one order.
• Demonstrated accuracy through test calculations using established self-energy approximations.

Conclusions:

• The developed technique offers significant computational advantages in terms of storage and scaling.
• The method introduces only minor errors when applied with quasiparticle virtual orbitals and conventional integral evaluation techniques.