Localized exchange-correlation potential from second-order self-energy for accurate Kohn-Sham energy gap

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate calculation of electronic properties like energy gaps is crucial for understanding material behavior.
• Existing methods, such as the local-density approximation (LDA), often struggle with accuracy for larger systems.
• The Kohn-Sham (KS) formalism provides a framework for electronic structure calculations but requires accurate exchange-correlation potentials.

Purpose of the Study:

• To derive a computationally efficient local Kohn-Sham (KS) exchange-correlation potential.
• To investigate the accuracy of this new potential for calculating KS energy gaps and lowest excitation energies.
• To assess the performance of the method for various system sizes, from atoms to medium-sized molecules.

Main Methods:

• Localization of the second-order self-energy operator using approximations to the linear response Sham-Schlüter equation.
• Application of the resolution-of-identity technique for efficient calculation of self-energy matrix elements.
• Investigation of KS energy gaps and lowest excitation energies for atoms and molecules.

Main Results:

• Excellent agreement was achieved for KS energy gaps of atoms and small molecules compared to reference values.
• The developed method demonstrates high efficiency, enabling application to larger and more complex systems.
• For larger systems, the calculated KS energy gap was found to be smaller than that predicted by the LDA.

Conclusions:

• The proposed local KS potential provides an accurate and efficient means to compute electronic excitation energies.
• The findings underscore the necessity of incorporating ab initio correlation effects for accurate KS energy gap predictions in larger systems.
• This method offers a promising avenue for reliable electronic structure calculations in condensed matter physics and quantum chemistry.