I agree, there is some confusion. There probably always is.
The confusion here is mainly about definition para-, dia-, ferro-,
antiferro-, heli-, or non- magnetic. This comes up every now and then.
As I said before, I like the following distinction.
a) Define Non-Magnetic ONLY in context of calculations, and there as a
model where in the converged ground state all local moments are smaller
than the numerical noise.
The rest were defined much earlier from an experimental point of view.
They all are meant to distinguish response to external magnetic field -
a field that DOES NOT EXIST in your off the shelf DFT!
b) Various kinds of dia- and para-magentism specify wether the
magnetization induced by an applied field is opposite (diamagnetic) or
parallel (paramagnetic) to the field.
c) Magnetically ordered states (FM, AFM of various types, ferri-, heli-,
spin density wave-, ...) are PM in this sense. They are distinguished by
the spacial arrangement of non-zero static magnetic moments (all
parallel, exactly compensated antiparallel, not compensated
antiparallel, not collinear, varying in size continuously, ...).
So in response to your points:
1.: Yes, but a PM response just might be due to some unnoticed AF
ordered state. Because of Ockham's razor one would have to convince me
of that, but who know's?
2.: Yes, you can get a non-magnetic ground state from a spin-resolved
calculation. 'Local moments' always refers to the moments within RMT's
(or whatever the DFT code supports to assign local moments). The
electron spins are of course always there, but spin up and down can
compensate - and often will compensate due to spin degenerate ground
states.
3.: No, I would be very surprised (and suspicious) if the calculations
yield some exactly compensating moment on S. For exact compensation,
that is an AF arrangement, you have to have the same element pointing
moments in opposite directions. Even the crystalografic lattice sites
occupied by the antiparallel moments should be the same. I know of no
counter example but would be interested if there is one. In VS Vanadium
just might split one of its sublattices into such an AF arrangement.
4.: There is a DOS plotted in the work A. Reggad linked in his earlier
question.
5.: That DOS certainely looks metalic and the authors claim agreement
with experiment.
Best regards,
Martin Pieper
---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564
Am 07.09.2017 11:02, schrieb E.A.Moore:
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-boun...@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-boun...@zeus.theochem.tuwien.ac.at] im Auftrag von
Abderrahmane Reggad [jazai...@gmail.com]
Gesendet: Donnerstag, 7. September 2017 00:26
An: wien@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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