Single Excitation Energies Obtained from the Ensemble "hOMO-LUMO Gap": Exact Results and Approximations

Tim Gould, Zahed Hashimi, Leeor Kronik, Stephen G. Dale

Research output: Contribution to journalArticlepeer-review

Abstract

In calculations based on density functional theory, the "HOMO-LUMO gap"(difference between the highest occupied and lowest unoccupied molecular orbital energies) is often used as a low-cost, ad hoc approximation for the lowest excitation energy. Here we show that a simple correction based on rigorous ensemble density functional theory makes the HOMO-LUMO gap exact in principle and significantly more accurate in practice. The introduced perturbative ensemble density functional theory approach predicts different and useful values for singlet-singlet and singlet-triplet excitations, using semilocal and hybrid approximations. Excitation energies are similar in quality to time-dependent density functional theory, especially at high fractions of exact exchange. The approach therefore offers an easy-to-implement and low-cost route to robust prediction of molecular excitation energies.

Original languageEnglish
Pages (from-to)2452-2458
Number of pages7
JournalJournal of Physical Chemistry Letters
Volume13
Issue number10
DOIs
StatePublished - 17 Mar 2022

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • Physical and Theoretical Chemistry

Fingerprint

Dive into the research topics of 'Single Excitation Energies Obtained from the Ensemble "hOMO-LUMO Gap": Exact Results and Approximations'. Together they form a unique fingerprint.

Cite this