[Wien] How to decrease interstitial charges?

[Rocquefelte]

Dear Ahmad,

Just to add one more comment. Such values are expected due to the high 
covalency of the chemical bond between carbon atoms in both graphene and 
diamond.

In fact, what you obtain is certainly values like (consider atom 1 as 
carbon):

CHA001 = 1.7  (which gives you the number of valence electron inside the 
MT sphere)

and

CTO001 = 3.7 (which gives you the number of total electron inside de MT 
sphere)

So as you mention 2 electrons are missing (in comparison to the atomic 
electronic structure 1s2 2s2 2p2), but the interaction is strong between 
carbon atoms (same electronegativity) and then an important part of the 
electronic density is in between the atoms (i.e. in the interstitial 
region). So a significant part of the charge should be in the 
interstitial region.

Lets take one of my examples to illustrate this feature. Sometimes ago I 
did calculation on vanadate compounds and the charge in the MT sphere of 
vanadium was as follow:

CHA = 1.818 for a vanadium 5+

CHA = 1.874 for a vanadium 4.5+

CHA = 1.899 for a vanadium 4+

As you see an increase of 1 electron in terms of formal charge lead to 
an increase of 0.081 electrons in the MT sphere !!!

So the variation is very small although in such a strong change from V5+ 
(with 3d0 electronic configuration) and V4+ (3d1).

So you can imagine that between graphene and diamond the change is 
smaller (same oxidation degree but different hybridation).

To conclude, when you are interested in the "real" charge of an atom you 
have to consider Bader charges or related tools (look at AIM program in 
WIEN2k).

Best regards

Xavier


Ahmad Ranjbar a écrit :
> Dear WIEN2K users,
>
> I am doing some electronic structure calculations on graphene sheet using WIEN2K.
> I am wondering if anybody can help me about my problem.
> The problem is as follow:
>
> My calculation shows that the total charge of carbon atom in muffin-tin sphere is about 4 electrons. It means that about 2 electron of Carbon atom is distributed in interstitial region. Is it correct for graphene?
> I checked it for Diamond. The result was same!!!
>
> If it is not correct How can i decrease the interstitial charges in my system. 
> Is it possible?
>
> I should mention that, for test calculation, i did SCF run for Iron Fe.
>
> CTO  : TOTAL   INTERSTITIAL CHARGE=    1.0301020
> TOTAL   CHARGE IN SPHERE  1 = 24.9698980
>
> As you see the total charge in muffin-tin sphere is about 25 electrons.
>
>
> Thank you very much for your help.
>
> Best regards,
>   
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