[Wien] exchange coupling constants calculations

[Linux PC]

Thank you Xavier and Guillaume.

One more small question. If I have ferromagnetic system (experimental data), calculated total energy in spinpolarized ferromagnetic system (let's call it E(SP)) then in order to get E(FM) from your formula, I have to calculate total energy of a non-spinpolarized system (E(NSP)), then I can calculate E(FM) like E(FM) = E(SP)-E(NSP). Am I right?

Thank you!

Date: Wed, 18 May 2011 14:11:18 +0200
From: Xavier.Rocquefelte at cnrs-imn.fr
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] exchange coupling constants calculations



  


    
  
  
    Dear Vincent,

    

    The rule is quite simple. Let's take the example of a monoatomic
    linear chain. 

    To obtain the J parameter coupling two adjacent magnetic centers,
    you simply have to do 2 calculations:

    

    - one with the ferromagnetic order: FM

    - one with the antiferromagnetic order: AFM

    

    You will then obtain two total energies, i.e. E(FM) and E(AFM). 

    

    Considering an Heisenberg Hamiltonian, you have:

    

    E(FM) = N²/4 * (-J)

    

    and 

    

    E(AFM) = N²/4 * (+J)

    

    Then E(AFM) - E(FM) = N²/4 * (2*J) = N²/2 * J

    

    where N is the number of unpaired electrons on the magnetic center.
    

    

    For example, for N = 1:

    

    J = 2 * (E(AFM) - E(FM))

    

    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:

    - to use more magnetic orders than unknown J parameters

    - to do a least-square procedure to find the J values ...

    

    Here is and example of calculations I did with Peter and Karlheinz
    on CuO:

    

    http://iopscience.iop.org/0953-8984/22/4/045502

    

    If you do not have access to the paper, I could send it to you. 

    

    Regards

    

    Xavier

    

    

    

    

    

    Le 18/05/2011 12:31, Linux PC a écrit :
    
      
      Dear Xavier,

      

      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.

      

      Thank you!

      Vincent

      

      > Date: Wed, 18 May 2011 07:24:52 +0200

      > From: Xavier.Rocquefelte at cnrs-imn.fr

      > To: wien at zeus.theochem.tuwien.ac.at

      > Subject: Re: [Wien] exchange coupling constants calculations

      > 

      > Dear Vincent,

      > 

      > Yes for sure. To estimate magnetic exchange coupling
      parameters you 

      > need to do a mapping based on total energies of different
      magnetic 

      > orders. WIEN2k allows to have total energies with high
      accuracy and 

      > using different functionals (depending of the system you are
      

      > considering). So yes, using WIEN2k to estimate J values is an
      

      > excellent choice.

      > 

      > Regards

      > 

      > Xavier

      > 

      > 

      > 

      > "Linux PC" <linuxfarm3m at hotmail.fr> a écrit :

      > 

      > >

      > >

      > > Dear Dr. Blaha and Wien2k users,

      > >

      > > Is it possible to use the Wien2k to calculate j magnetic
      exchange 

      > > coupling constants?

      > >

      > > Thank you very much,

      > > Vincent

      > >

      > 

      > 

      > _______________________________________________

      > Wien mailing list

      > Wien at zeus.theochem.tuwien.ac.at

      > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien

      
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