It maybe you meant oxidation state or even charge, not valence?

Dear Oleg,

I know that in chemistry there is a rule when both are equal but now I don't remember the exact rule. I believe that in this case valence state is synonymous of oxidation number. 

Dear Maximo,

I guess you can extrapolate this kind of information through a Bader charge analysis.

http://theory.cm.utexas.edu/henkelman/code/bader/

The Bader charges should be correlated to the formal oxidation states. Typically the bader charges are significantly reduced however, because electrons do not sit entirely on the metal centers.

Often, however, you may observe that various metallic atoms, that are expected to have different oxidation states, have very close Bader charge. Make sure that your Mn atoms really are in the oxidation state that you think they are. You can do this, for example, using the DFT+U method and looking at the on-site occupancies, as well as the spin states. The on-site occupancy or magnetization from DFT+U is better for distinguishing different oxidation states of 3d metals.

It could be that Bader charge variations between two different oxidation states are very small, depending on the local environment. The small difference you found between different oxidation states has a fundamental reason. It is the so-called charge-self regulation mechanism. Essentially if you go from Mn4+ to Mn3+ anticipating a change of 1 in the bader charge, then this does not happen and most of the extra one electron is distributed among the surrounding ligands.

Best,

A.

Dear Angelo,

Thanks for the code that you suggest me. But after run bader I have three files, ACF.dat, BCF.dat and AVF.dat. In the bader page suggest use VESTA to visualize.

But now, How can I get the oxidation value of Mn?

Dear Maximo,

the 5th column of ACF.dat output file should be contain the CHARGE of each atoms belonging to the unit cell. I guess it refers to the outer electronic shell, so the maximum number of charge you can find is about 8 (from the octet rule). It is not exactly 8, but more or less close to it, if shell is full.

For example, I am attaching NaCl example file. Here, the sum charge of every couple of Na and Cl atoms is approximately 16 (full outer shells of both!). So that, the charge number is representative of the valence or oxidation number of that element, but at the same time it takes into account of such interaction between the electronic clouds.

In Mn case, it may be not very clear the difference in charge between the two different oxidation states, but there will be an evident difference. Usually, if the oxidation state is the same, you find out charge difference in hundredth. I don’t know to quantify how much has to be the difference in charge in your case!

I hope this can be useful.

Greetings,

A.

Dear Angelo,

Thanks for the example. I search Mn charge and ACF.dat file and I get the average or Mn charge is about 5.08988475, but I expecting around 3.5.

You have an idea why the difference?

And also you know any good resource about INPUT parameters to get accuracy valence in VASP?

 Dear Maximo,

I've not an exact idea about what happens in this case. As I said before it can depend on the environment interacting with Mn atoms, different electronegativity of atoms involved can produce a "strange" delocalization of the electronic clouds. Furthermore, this analysis is influenced by the kind of exchange-correlation functional used in DFT calc. As suggested you can try using Hubbard correction U. 

About the second question, no I don't. I used just to set the occupation number manually, according Hund rules, if system didn't work very well.

Best,

A.

Dear Angelo,

Thanks again. About

I used just to set the occupation number manually, according Hund rules

Can you please explain a little more this?

Dear Maximo,

I carried out this operation not using VASP but another DFT package called Quantum Espresso. There, it was possible to set in the INPUT file for DFT run also the "occupation number" manually. Usually it was set automatically, but in case you needed to specify how the orbitals of atoms had to be filled, you could do this. I guess there is a FLAG in the INPUT file which allows you this operation, even in VASP package.

Inserting manually this occupation numbers you give to the code, fixed numbers (integer) for the occupation state of a specific orbital of your system. In this way you let avoid mixing in the occupation valence bands, making much simple the reaching of convergence and probably, it could be useful for getting a more significant result in oxidation numbers.

Best,

A.

Dear Angelo,

I have used Quantum Espresso in the past. "occupation number" select smooth function, in VASP is called ISMEAR.

Thanks! I let you know if I can get the oxidation number or valence state.

Dear Maximo,

The easiest way to describe the oxidation state is looking at the magnetic

moments. The charges, for instance,  Bader charges, will almost always

different then the "oxidation states". A Careful look at the magnetic

moments(after correct setting magmom), integrated DOS(upto Fermi level) and PDOS will give you the

correct answer.

You can write to me for more details.

Thanks Dear Mudit. I will try your suggestions.

Here, I have one Quarry, how To calculate the PDOS from Vasp ?

Dear Mudit Dixit ,

I have done calculation of lower valence dopant like Eu+3 in W+6. We are experimentally getting by XPS study oxidation state is changing of W element.

Can we say by looking bader charge, oxidation state of host material is changing after doping by comparing bader charge of pure W and after dopant.

Any DFT paper regarding calculation of oxidation state ?

Thank You

Shilendra

Hi Shilendra,

Please see the section S1 (supporting info) of my recent paper regarding the calculation of oxidation states.

Article The Origin of Structural Degradation during Cycling and Low ...

http://pubs.acs.org/doi/suppl/10.1021/acs.jpcc.7b06122/suppl_file/jp7b06122_si_001.pdf

Dear Mudit,

Thank you for your kind help !

I will go through this supporting information. If I will have any doubt, I will ask you.

Shilendra

Dear Mudit,

Here I want to ask one doubt. VASP gives magnetic moment in OSZICAR as well as total magnetic moment (by using LORBIT=11) in OUTCAR. Which one is true magnetic moment of system. Which magnetic moment we should report in paper.

I went to your supporting information in which you are correlating magnetic moment with oxidation state in 4 different system. Magnetic moment is the only criteria for looking change in oxidation state or any other.

For example I am doping A elemrnt in B then after doping my B element is changing oxidation state then how will confirm by looking magnetic moment before and after dopant . After dopant if magnetic moment is increasing means oxidation state is increasing and how much is increasing ? How will confirm oxidation state.

Thank You

Shilendra