Multiwfn forum

jesswade

Member

Registered: 2020-05-11

Posts: 3

Extract magnetic dipole?

Hello everyone, I wondered if it was possible to use Multiwfn to visualise the magnetic dipole moment of a molecule/oligomer, in a similar way to how you can visualise the electronic dipole moment using Gaussian? I can see the details of the mag. dipole are in the .log/.chk/.fchk file, but can't work out how to show it alongside the e-dipole.

Thanks!

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,775

Website

Re: Extract magnetic dipole?

There is not mag. dipole moment in Gaussian log file, and it is impossible to visualize mag. dipole moment. For an isolated molecule, you can only discuss magnitude of mag. dipole moment, which is proportional to spin quantum number S.

jesswade

Member

Registered: 2020-05-11

Posts: 3

Re: Extract magnetic dipole?

Just to confirm, I mean magnetic transition dipole moment?

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,775

Website

Re: Extract magnetic dipole?

In Multiwfn, transition magnetic dipole moment can be calculated via hole-electron analysis module. Specifically, enter the hole-electron analysis module (subfunction 1 of main function 18), choose option "-1 Toggle calculating transit. magnetic dip. density in option 1" once to switch its status to "Yes", then select option 1 to start calculation of grid data, then from the final output you can find transition magnetic dipole moment:

Integral of hole: 0.999620
Integral of electron: 1.002670
Integral of transition density: -0.000147
Transition dipole moment in X/Y/Z: 0.000123 0.000806 -0.000612 a.u.
Transition magnetic dipole moment in X/Y/Z: 0.043691 -0.593374 0.003183 a.u.
Sm index (integral of Sm function): 0.26984 a.u.
Sr index (integral of Sr function): 0.51772 a.u.
Centroid of hole in X/Y/Z: 0.001884 2.596265 -0.000373 Angstrom
...

If you are not familiar with hole-electron analysis module, please follow example of Section 4.18.1 of manual.

If you want to plot an arrow of transition magnetic dipole moment to graphically indicate its vector, you can use drawing command in VMD; alternatively, you can manually replace dipole moment in Gaussian output file by transition magnetic dipole moment, then the dipole moment shown in GaussView will correspond to transition magnetic dipole moment.

jesswade

Member

Registered: 2020-05-11

Posts: 3

Re: Extract magnetic dipole?

Thank you, that is great! One more question. The magnetic transition dipole coordinates in the log file from Gaussian (for a particular transition) are not the same as the Transition magnetic dipole moment in X/Y/Z that the hole-electron analysis module outputs (for the same transition). Is there a reason for that?

It is awesome being able to visualise it using Gaussian, I am very grateful.

p.s. I liked your article on the ChemRXiv.

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,775

Website

Re: Extract magnetic dipole?

As an example, from examples\excit\4-nitroaniline.out in Multiwfn package you can find

Ground to excited state transition magnetic dipole moments (Au): state X Y Z 1 -0.0005 -0.6038 0.0000 2 0.0000 0.0000 0.0142 3 0.0000 0.0000 1.0441

If you use hole-electron analysis module based on examples\excit\4-nitroaniline.fch and examples\excit\4-nitroaniline.out to perform the analysis for the 1st excited state as I previously mentioned, the result is

Transition magnetic dipole moment in X/Y/Z: 0.002707 -0.603690 0.000918 a.u.

There is no evident difference with the 0.0005 -0.6038 0.0000 outputted by Gaussian. The marginal difference comes from the fact that hole-electron analysis module calculates this quantity based on integral of evenly distributed grid, while Gaussian calculates it analytically. If you find the difference is really large, please make sure that you have used IOp(9/40=4).