Accurate solid-state band gaps via screened hybrid electronic structure calculations

Area of Science:

• Solid-state physics
• Quantum chemistry
• Computational materials science

Background:

• Accurate calculation of band energy differences in solids is crucial for predicting material properties.
• Screened hybrid density functionals, such as HSE, have shown promise in reproducing experimental band gaps.
• The theoretical underpinnings of this accuracy have not been fully elucidated.

Purpose of the Study:

• To rationalize the high accuracy of screened hybrid functionals in predicting solid band gaps.
• To establish a connection between screened hybrid functionals and time-dependent density functional theory (TD-DFT) calculations.
• To validate the predictive power of these methods for experimental optical absorption spectra.

Main Methods:

• Generalized Kohn-Sham (GKS) calculations using screened hybrid density functionals (e.g., HSE).
• Time-dependent density functional theory (TD-DFT) calculations with unscreened functionals.
• Comparison of calculated band energy differences with experimental band gaps and optical absorption spectra.

Main Results:

• Band energy differences from GKS calculations with screened exchange functionals closely approximate excitation energies from TD-DFT with unscreened functionals.
• TD-DFT calculations with unscreened functionals are expected to accurately predict experimental optical absorption spectra.
• The standard HSE screening parameter (omega=0.11 bohr(-1)) offers a good balance across various material systems, despite system-dependent optimal values.

Conclusions:

• The accuracy of HSE-type functionals in predicting band gaps is rationalized by their connection to accurate excitation energy calculations.
• Screened hybrid functionals provide a computationally efficient route to predicting optical properties.
• The standard HSE parameter is a reliable choice for diverse materials, facilitating broader application.