oxidation states

[daniel_aravena]

Dear All,

I want to perform some calculations on iron(II) complexes so i should set a d6s0 electronic configuration for iron, it is possible to change orbital occupancies in the basis set but it looks like you can define only one basis set per element, my question is:

is it possible to define two (or more) basis sets with diffrent occupancies for the same element?,

Thanks
Daniel

[Anders Blom]

Yes, it can be done. It's a bit tricky, however, so let me get back to you on it

[Nordland]

I think I can help you, but I am must be sure of what exactly you are asking.

Do you want a different basis set for each iron atom in the cell or do you want a basis set for iron with a different occupations?

[daniel_aravena]

I want to define different occupancies for the same element using the same basis set. Anyway, it would be great to know how to set different basis sets in general.

[Nordland]

A good starting tip to get you started, can be to use the scripter and set the "Script Detail" to "Show Defaults". Then you will be able to customize it all in all the details you want.

[Nordland]

This is how I would do it.

• Create a Iron(II) element using all the properties from Iron.
• Used the DZP basis set for Iron, to create another basis set for Iron(II) with a different occupation
• And go!

Code: python

###############################################################
# Creating a second Iron element.
###############################################################
class Iron2(Iron):
    @staticmethod
    def symbol(): return 'Fe(II)'

# Replace the Iron with Iron(II) for atom 2 and 4.
bulk_configuration.elements()[2] = Iron2
bulk_configuration.elements()[4] = Iron2

# It is required in ATK 10.8.0 to insert this snippet in order 
# for it work properly. This is not required in newer versions.
def symbols(self): return [x.symbol() for x in self.elements()]
BulkConfiguration.symbols = symbols

###############################################################
# Setting up a basis set for Iron(II) starting from the 
# Iron DZP basis set, but using a the new element, and
# a new occupation.
###############################################################
iron2_dzp = LDABasis.Iron_DoubleZetaPolarized(element=Iron2,
                                             occupations=[8.0,0.0,0.0,0.0,0.0])
basis_set = [ iron2_dzp ] + LDABasis.DoubleZetaPolarized

However there are a few pitfalls to avoid:

• If you adjust the occupation of the orbitals, you have to consider using a different pseudo-potential for the Iron(II) element to get the best results.
• There is no support for saving the SCF results, and restarting from it when using a custom element. Therefore you have to select all the analysis up-front

I have attached a script where I use this approach on a LiFe2F6 crystal.

[daniel_aravena]

that was exactly what i needed, thank you very much

[Nordland]

You are welcome