Fundamental gaps of finite systems from the eigenvalues of a generalized Kohn-Sham method

TL;DR

This paper introduces a physically-motivated first-principles method using a range-separated hybrid functional within generalized Kohn-Sham density functional theory to accurately determine the fundamental gap of finite systems.

Contribution

It proposes a novel approach that adjusts the range-separation parameter to satisfy Koopmans' theorem for both neutral and anionic states, extending DFT's applicability.

Findings

Accurately predicts fundamental gaps for atoms, molecules, and nanocrystals.

Demonstrates improved agreement with experimental data.

Extends the practical use of density functional theory to new areas.

Abstract

We present a broadly-applicable, physically-motivated first-principles approach to determining the fundamental gap of finite systems. The approach is based on using a range-separated hybrid functional within the generalized Kohn-Sham approach to density functional theory. Its key element is the choice of a range-separation parameter such that Koopmans' theorem for both the neutral and anionic is obeyed as closely as possible. We demonstrate the validity, accuracy, and advantages of this approach on first, second, and third row atoms, the oligoacene family of molecules, and a set of hydrogen-passivated silicon nanocrystals. This extends the quantitative usage of density functional theory to an area long believed to be outside its reach.