Design of auxiliary systems for spectroscopy

Area of Science:

• Computational Physics
• Quantum Chemistry
• Materials Science

Background:

• The Kohn-Sham system is a successful auxiliary model for electronic density calculations.
• Current methods like TDDFT and MBPT often compute more data than needed for spectral analysis.
• Excited-state properties are not directly described by the standard Kohn-Sham system.

Purpose of the Study:

• To propose a generalization of the Kohn-Sham approach.
• To develop auxiliary systems that target specific spectral properties directly.
• To simplify calculations for spectroscopy by avoiding unnecessary data computation.

Main Methods:

• Designing generalized auxiliary systems with tailored effective potentials or kernels.
• Focusing on simplified effective kernels for optical absorption.
• Developing spectral potentials for photoemission spectra.
• Expressing these potentials/kernels as functionals of the electronic density.

Main Results:

• Demonstrated the feasibility of creating simplified auxiliary systems for specific spectral properties.
• Showcased prototypical applications for optical absorption and photoemission.
• Established a framework for density-functional approximations of these targeted spectral properties.

Conclusions:

• The generalized Kohn-Sham approach offers a more efficient route to spectral properties.
• Simplified auxiliary systems can significantly reduce computational cost in spectroscopy.
• This work provides a pathway for developing targeted, accurate spectral calculations.