Bader Analysis and ADDGRID and PREC tag

[shilu]

Dear Prof. Graeme,

I have few confusion regarding Bader charge analysis. I have two system pure WO3 and Eu doped WO3. I want to check effect of Eu doping on W bader charge. If I am calculating bader charge by giving ADDGRID tag and other common tag LAECHG=T etc.in VASP code then I am getting difference on W atom bader charge before and after doping much like before doping charge on W in ACF.dat file 8.8 and after doping 10.5 etc.

But when I am giving without ADDGRID tag then difference in bader charge is very less before and after doping like 9.03 and 9.07 etc. Other case I am not giving ADDGRID tag but I am giving PREC=Accurate then also difference in charge on W is very less or almost equal before and after doping.

Since W is in +6 oxidation state and Eu is in +3 state. So after doping oxidation state of W should change and hence bader charge on W should change before and after doping of Eu.

Another case if I am increasing values of NCXF NGYF and NGXZ then charge on W is going to be almost equal before and after doping. At how much less difference we can say W is chaning oxidation state by looking bader charge.

What parameters should I take for calculating bader charge.

I am calculating bader charge is like as

bader charge=number of valance electrons in POTCAR on that atom- charge on that atom in ACF.dat file after bader calculation over.

Am I calculating bader charge right ?

Thank You
Shilendra

[graeme]

First, make sure that you are doing the analysis on the total charge an integrating the valence charge, as in:

bader CHGCAR -ref CHGCAR_sum

where CHGCAR_sum is generated through:

chgsum.pl AECCAR0 AECCAR2

Then, if you still have problems, you can upload the charge density files so I can take a look.

[shilu]

Dear Prof. Graeme

I am following same procedure as you mentioned by taking AECARR0 AECARR2 and CHGCAR file. I am getting different bader charge for different ADDGRID and PREC options. I am getting very less difference in bader charge wirh and without doping only 0.03. But according to hypothesis and based on XPS results W is changing its oxidation state by Eu doping. So I should get significant difference in bader charge.

I have attached here all my files with and without doping. I took ADDGRID = False and PREC= Accurate in my calculation.

I want to confirm bader charge calculation, I am calculating bader charge as following.

Bader charge= Number of valance electron (ZVAL) of that atom in POTCAR - Charge on that atom in ACF.dat file after bader charge calculation

Can we visualize bader charge ? What else information can we get from bader charge calculation ?

Thank You

Shilendra

[shilu]

Dear Prof. Graeme

I cleared my above doubts. Since I was looking only bader charge difference on W atoms which is very less but Eu is changing much bader charge compare with Eu+2 and +3 states which should be in my case.

Here I want to ask my another query. What else information (except bader charge) can we get from bader charge calculation output files ACF.dat and BCF.dat. Is there any parameter we can visualize and by which software.

How can I calculate charge transfer in two system one is pure and other one is doped. I want to check dopant effect in charge transfer.


Thank You
Shilendra

[graeme]

You can write the Bader volumes to a charge-density like file using the "-p all_atom" or "-p atom_index". These can be visualized using any program that can read chgcar files, including vesta or vaspview.