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

Fri Sep 8 09:57:27 CEST 2017

I would say that -cc 0.001 -ec 0.001 are certainly too large.

Also, a more subtle point. When you say you use "-eece" what hybrid
fraction? Is that the right fraction? How do you know if it is the right
value to use?

On Sep 8, 2017 9:13 AM, "Fecher, Gerhard" <fecher at uni-mainz.de> wrote:

> Now I am a little confused
> do you think that it was the convergence criteria that I found a magnetic
> moment of 2.5 mu_B instead of 0.05 mu_B at the V ?
> or did I make another mistake ;-)
>
> Indeed, you are right, the 0.05 mu_B might be a result of to bad
> convergence
> however, to check if such a moment is something reliable you will need
> brute force with respect to the number of k-points,
> that is, if you think you have enough k-points, then just double the
> number or use ten times more.
>
> Ciao
> Gerhard
>
> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
> "I think the problem, to be quite honest with you,
> is that you have never actually known what the question is."
>
> ====================================
> Dr. Gerhard H. Fecher
> Institut of Inorganic and Analytical Chemistry
> Johannes Gutenberg - University
> 55099 Mainz
> and
> Max Planck Institute for Chemical Physics of Solids
> 01187 Dresden
> ________________________________________
> Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Gavin
> Abo [gsabo at crimson.ua.edu]
> Gesendet: Freitag, 8. September 2017 03:14
> An: wien at zeus.theochem.tuwien.ac.at
> Betreff: Re: [Wien] About the magnetic moment of vanadium in vanadium
> sulphide
>
> 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.
>
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>
> 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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