Understanding and reducing errors in density functional calculations

TL;DR

This paper analyzes the sources of errors in density functional theory calculations, highlighting when density-driven errors dominate and how using more accurate densities can improve results.

Contribution

It introduces a decomposition of DFT errors into functional and density-driven components, emphasizing the importance of addressing density errors in certain cases.

Findings

Density-driven errors often dominate in specific cases.

Using more accurate densities can significantly reduce errors.

Small orbital gaps indicate potential density-driven errors.

Abstract

We decompose the energy error of any variational DFT calculation into a contribution due to the approximate functional and that due to the approximate density. Typically, the functional error dominates, but in many interesting situations, the density-driven error dominates. Examples range from calculations of electron affinities to preferred geometries of ions and radicals in solution. In these abnormal cases, the DFT error can be greatly reduced by using a more accurate density. A small orbital gap often indicates a substantial density-driven error.