Electronic spin in Pseudopotentials (SIESTA)


I’m a recent user of the SIESTA code and I would like to ask for some help. I’m trying to perform some QM/MM simulations on a system containing an Fe 2+ ion.

I would like to know if there is some option, even in SIESTA or in ATOM, to specify the electronic spin state for Fe 2+ (high spin or low spin).

Probably I’m trying to use the SIESTA code for something that it is not intended to be used for. Using ATOM i managed to prepare pseudopotentials for Fe in its GS and even for Fe 2+ (just for testing purpouses). Nevertheless, I did not managed to find any way to describe Fe 2+ of low and high spin. Is there any way to do that in SIESTA? Maybe in the PAO.basis block?

Any help/idea will be appreciated, thank you

Aitor Valdivia

I do know the system you are working on.

In principle, you should not have a particular pseudo to describe a system in which you have Fe2+.
SIESTA can calculate the net atomic populations on each atom of the system, please check “Voronoi and Hirshfeld atomic population analysis” in the manual.

Additionally, you can use the flag “NetCharge” to change the charge of the whole system.

To set up the initial spin in SIESTA you should use the DM.InitSpin block (related to this block check also SpinPolarized option).

For Iron you might need to include semicore electronic in valence when generating the psuedos.

Hope this will help.

Thank you so much for the suggestions! It was very helpful.

I managed also to specify a specific spin multiplicity and fix it during the calculation (in fact, that was my intention for the tests I was performing).

Aitor Valdivia