Simplified, Physically Motivated, and Broadly Applicable Range-Separation Tuning

TL;DR

This paper introduces a simple, density-based method for tuning range-separated hybrid functionals in DFT, improving efficiency and accuracy for excited-state calculations in large systems without the need for multiple self-consistent calculations.

Contribution

It presents a novel, physically motivated approach to determine the screening parameter using only the electron density and the compressibility sum rule, simplifying and broadening the applicability of RSH functionals.

Findings

Achieves high accuracy for charge-transfer excitations

Outperforms previous tuning methods in efficiency and stability

Applicable to large and complex systems like bulk solids

Abstract

Range-separated hybrid functionals (RSH) with ``ionization energy'' and/or ``optimal tuning'' of the screening parameter have proven to be among the most practical and accurate approaches for describing excited-state properties across a wide range of systems, including condensed matter. However, this method typically requires multiple self-consistent calculations and can become computationally expensive and unstable, particularly for extended systems. In this work, we propose a very simple and efficient alternative approach to determine the screening parameter for RSH based solely on the total electron density of the system and the compressibility sum rule of density functional theory (DFT). This effective screening parameter achieves remarkable accuracy, particularly for charge-transfer excitations, surpassing the performance of previously suggested alternatives. Because it relies only on the electron density, the proposed approach is physically transparent and highly practical to automate DFT calculations in large and complex systems, including bulk solids, where ``tuning'' is not possible.