[Wien] About the magnetic moment of vanadium in vanadium sulphide

[Gavin Abo]

Perhaps the -ec 0.001 and -cc 0.001 are too large of values.

As I recall, to be well-converged, it is usually best to use about the 
default values seen in the post [1] or WIEN2k 17.1 usersguide [2] as:

-cc 0.0001
-ec 0.0001

It sounded like about the default value for -ec was good unless 
something like -ec 0.00001 was desired to reduce numerical noise, but 
anything smaller seemed useless [3,4].

For -cc, 0.00001 also may be the lowest limit [5] and quite ambitious to 
try to use [6].

In section "4.5.4 Antiferromagnetic (AFM) calculations" on page 46 in 
the usersguide [2], there is the statement:

"If nothing changes (E-tot and other properties), then you are ok, 
otherwise make sure the scf calculation is well converged (-cc 0.0001 or 
better)."

If I read from the statement correctly, a well converged scf calculation 
typically uses -cc with a value of 0.0001 or smaller. Though, there is a 
realistic limit as mentioned above on how small it could be set.

In [7], it sounded important that the -cc value was low for the :MMIn 
values.

So, maybe the calculation can still converge further such that possibly 
the "MMI for V1" and "MMI for V2" will both become zero when they reach 
better convergence.

[1] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg12620.html
[2] http://susi.theochem.tuwien.ac.at/reg_user/textbooks/usersguide.pdf
[3] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg10650.html
[4] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg16077.html
[5] 
http://zeus.theochem.tuwien.ac.at/pipermail/wien/2008-November/011797.html
[6] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg11558.html
[7] 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg09231.html

On 9/7/2017 9:11 AM, Abderrahmane Reggad wrote:
> Hi All
>
> I have used the PBE+EECC calculation for 3 configurations: nm, fm and 
> afm I and I found that the afm I is the most stable.
>
> The energy criterion and charge are 0.001 Ry and 0.001 e respectively.
>
> I don't worry about if the material is really antiferromagnetic or 
> paramagnetic because of:
>
> 1- I found only one experimental study that they found the compound to 
> be pauli magnetic and one theoritical study which they found the 
> compound to be non magnetic and these two studies are not sufficient 
> to judge the compound to be in a such state. The theoritical study 
> used the GGA method which is not good for correlated systems.
>
> 2- In the anfiferromagnetic state afm I in the NiAs structure for 
> vanadium sulphide I found the following results:
>
> MMI for V1: 0.05 MB
> MMI for V2 :- 0.05 MB
> MMI for S:    0 MB
>
> My questions are now:
>
> what's the definition of non magnetic compound ?
>
> I think we can talk about non magnetic calculation and not about non 
> magnetic compounds.
>
> As Blaha said we can't silulate the paramagnetic state or at at least 
> it's difficult to do it because we can't orientate the spins randomly 
> ang maintain the total magnetic moment equals to zero.
>
> Because of the Hind's prediction and because the impaired number of 
> the V2+ ion to equal 3 I believe the atomic magnetic moment to be 
> different from zero.
>
> Best regards
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