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

Thu Sep 7 12:00:30 CEST 2017

 I am used to setting up calculations with spins set to be parallel or antiparallel to each other and I would probably class those set up with antiparallel spins as AFM. You can also set up calculations that don't include spin and so will not have any magnetic moments. I tend to regard these as nonmagnetic calculations. However I take the point that something set up as AFM could turn out to have a 0 magnetic moment. 

Sorry you are right it should be the V magnetic moments that balance out. 

A Pauli paramagnet should have 0 magnetic moment from these calculations (it could be antiferromagnetic or nonmagnetic) as the magnetic moment is only produced when a magnetic field is applied.

-----Original Message-----
From: Wien [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Fecher, Gerhard
Sent: 07 September 2017 10:39
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] About the magnetic moment of vanadium in vanadium sulphide

Sorry but there is obviously a lot of nonsense in the comments where you should first think about:

Please explain why a spin polarized calculation will always result in a ferromagnetic (or antiferromagnetic) state ? How do you define a ferromagnet (or antiferromagnet) ?  
What happens when the magnetic part of the Hamilton becomes Zero in a spin polarized calculation ? What is a ferromagnet or antiferromagnet without magnetic moments at the atoms ?
Why should a paramagnet become an antiferromagnet in the calculation ?

Why is VS an antiferromagnet when V has a magnetic moment of 0.05 muB and S one of -0.05 muB ? Don't you think it is possible that the magnetisation of two V atoms may have to cancel ?

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 E.A.Moore [e.a.moore at open.ac.uk]
Gesendet: Donnerstag, 7. September 2017 11:02
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] About the magnetic moment of vanadium in vanadium sulphide

I have been following this thread and I think there is some confusion.

1. On the thread it said that the experiment showed it was Pauli paramagnetic. This is the type of magnetism displayed by some metals e.g. sodium which is only apparent if you apply a magnetic field.

2. If you include spin in your calculation (GGA or GGA + U) you can only get ferromagnetic, antiferromagnetic or ferromagnetic states. (An earlier thread deals with how to get paramagnetic states). I think you can only get a nonmagnetic state if you do not include spin? A material with Pauli paramagnetism will be antiferromagnetic in straight forward spin-including calculations.

3. I assume the 0.05 muB refers to the magnetic moment on V. If vanadium sulphide is antiferromagnetic and the magnetic moment on Vanadium is 0.05 muB, then there must be a balancing magnetic moment on the sulphur.

4. I suspect this compound might be alloy-like. Is there considerable mixing of V and S in the valence bands?

5. Assuming your formula is VS, it might be worth noting that VO shows some metallic physical properties.

Elaine A. Moore
Reader in theoretical chemistry
The Open University

-----Original Message-----
From: Wien [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Fecher, Gerhard
Sent: 07 September 2017 08:12
To: A Mailing list for WIEN2k users
Subject: Re: [Wien] About the magnetic moment of vanadium in vanadium sulphide

0.05 muB does not mean that it is antiferromagnetic ! what was your charge convergence criterion ?

You did never answer my question whether you started the EECE calculation from a converged GGA calculation.

Why do you like to have an afm state when the experiment tells it is not ?

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 Abderrahmane Reggad [jazairdz at gmail.com]
Gesendet: Donnerstag, 7. September 2017 00:26
An: wien at zeus.theochem.tuwien.ac.at
Betreff: Re: [Wien] About the magnetic moment of vanadium in vanadium sulphide

Hi Martin

The problem is that I want to know if it's possible to get a such value of 0.05 MB for atomic magnetic moment for the AFM state of vanadium sulphide in NiAs structure.

Hafner and Hobbs have found all the calculations converged to the non magnetic state because they have used the GGA method. To get the AFM state they have to use either the EECE or GGA+U methods.

I hope you touch the problem

Best regards
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