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Dear Vincent,<br>
<br>
The rule is quite simple. Let's take the example of a monoatomic
linear chain. <br>
To obtain the J parameter coupling two adjacent magnetic centers,
you simply have to do 2 calculations:<br>
<br>
- one with the ferromagnetic order: FM<br>
- one with the antiferromagnetic order: AFM<br>
<br>
You will then obtain two total energies, i.e. E(FM) and E(AFM). <br>
<br>
Considering an Heisenberg Hamiltonian, you have:<br>
<br>
E(FM) = N²/4 * (-J)<br>
<br>
and <br>
<br>
E(AFM) = N²/4 * (+J)<br>
<br>
Then E(AFM) - E(FM) = N²/4 * (2*J) = N²/2 * J<br>
<br>
where N is the number of unpaired electrons on the magnetic center.
<br>
<br>
For example, for N = 1:<br>
<br>
J = 2 * (E(AFM) - E(FM))<br>
<br>
The present example is very simple and you could imagine that for
more complex structures it will be more difficult to realize a
mapping analysis. Then the idea is:<br>
- to use more magnetic orders than unknown J parameters<br>
- to do a least-square procedure to find the J values ...<br>
<br>
Here is and example of calculations I did with Peter and Karlheinz
on CuO:<br>
<br>
<a class="moz-txt-link-freetext" href="http://iopscience.iop.org/0953-8984/22/4/045502">http://iopscience.iop.org/0953-8984/22/4/045502</a><br>
<br>
If you do not have access to the paper, I could send it to you. <br>
<br>
Regards<br>
<br>
Xavier<br>
<br>
<br>
<br>
<br>
<br>
Le 18/05/2011 12:31, Linux PC a écrit :
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Dear Xavier,<br>
<br>
Thank you very much for the answer! I actually was looking through
the manual before, unfortunately, did not succeed in finding any
information on exchange interactions. Would you know, or may be
other users, if any practical manual exists for calculating of J.<br>
<br>
Thank you!<br>
Vincent<br>
<br>
> Date: Wed, 18 May 2011 07:24:52 +0200<br>
> From: <a class="moz-txt-link-abbreviated" href="mailto:Xavier.Rocquefelte@cnrs-imn.fr">Xavier.Rocquefelte@cnrs-imn.fr</a><br>
> To: <a class="moz-txt-link-abbreviated" href="mailto:wien@zeus.theochem.tuwien.ac.at">wien@zeus.theochem.tuwien.ac.at</a><br>
> Subject: Re: [Wien] exchange coupling constants calculations<br>
> <br>
> Dear Vincent,<br>
> <br>
> Yes for sure. To estimate magnetic exchange coupling
parameters you <br>
> need to do a mapping based on total energies of different
magnetic <br>
> orders. WIEN2k allows to have total energies with high
accuracy and <br>
> using different functionals (depending of the system you are
<br>
> considering). So yes, using WIEN2k to estimate J values is an
<br>
> excellent choice.<br>
> <br>
> Regards<br>
> <br>
> Xavier<br>
> <br>
> <br>
> <br>
> "Linux PC" <a class="moz-txt-link-rfc2396E" href="mailto:linuxfarm3m@hotmail.fr"><linuxfarm3m@hotmail.fr></a> a écrit :<br>
> <br>
> ><br>
> ><br>
> > Dear Dr. Blaha and Wien2k users,<br>
> ><br>
> > Is it possible to use the Wien2k to calculate j magnetic
exchange <br>
> > coupling constants?<br>
> ><br>
> > Thank you very much,<br>
> > Vincent<br>
> ><br>
> <br>
> <br>
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