Multiwfn forum

fyzan

Member

Registered: 2020-01-25

Posts: 21

Excitation energies are less than frontier orbital energies

Dear sir, the excitation energies are much less than frontier orbitals energy difference. like for excited state 1 the excitation energy is 5.0615 eV in the example file of N-phenylpyrrole.out present in Multiwfn example/excit folder but its HOMO (38)-LUMO (39) energy gap is 7.754761768 eV. How to explain these results?

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

Website

Re: Excitation energies are less than frontier orbital energies

Even if the excitation is only contributed by HOMO-LUMO transition, the excitation energy and HOMO-LUMO gap are still different, because they differ with each other by excition binding energy, see Section 2 of this post: http://bbs.keinsci.com/thread-16758-1-1.html