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Mvr2301

Member

Registered: 2020-10-18

Posts: 4

Electron and Hole Distribution and Molecular Orbitals?

I am running some theoretical calculations on Organic Molecules. The calculations were based on Gaussian and Multiwfn. I just want to know the difference between the Molecular orbitals (HOMO and LUMO) which were shown in the Gaussian software itself, and the electron-hole distribution. what is the advantage or information of hole-electron distribution of a molecule?

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,631

Website

Re: Electron and Hole Distribution and Molecular Orbitals?

In many cases, there is no dominant MO transition in the excitation. For example, in practice, you may find HOMO->LUMO, HOMO-2->LUMO, HOMO->LUMO+1 contribute to S0->S1 excitation by 50%, 20%, 30%, respectively. Clearly in this case it is not possible to characterize the excitation by simply viewing one pair of MOs. Hole-electron analysis in Multiwfn provides significant conveniences, because for any electron excitation, this method is able to represent the excitation as a "hole" to "electron" transition, namely you can always intuitively understand the character of the excitation by examining hole and electron distributions (usually in terms of isosurface map). In addition, hole-electron analysis module is able to present rich quantitative information about the excitation, such as D index, Sr index, centroid position of hole and electron, exciton binding energy and so on, which are quite useful in quantitatively compare various electronic excitations. Please check introduction of the hole-electron analysis in Section 3.21.1 of the Multiwfn manual for more information, and you will recognize the power and usefulness of the hole-electron analysis by carefully following Section 4.18.1 of the manual.

A very good example is my publication Carbon, 165, 461-467 (2020) https://doi.org/10.1016/j.carbon.2020.05.023. As you can see from Fig. 4, S0->S21 excitation of the cyclo[18]carbon is nearly equally contributed by four pairs of MO transitions, while by using the hole-electron analysis, this complicated excitation can be exhibited as a single map very clearly, namely Fig. 6(b).

evetaylor

Member

Registered: 2024-02-05

Posts: 2

Re: Electron and Hole Distribution and Molecular Orbitals?

Thank you for the explanation and the suggestinos.  I'll definitely look into the resources you shared.