[Pw_forum] About NON COLLINEAR magnetism

[xianghjun]

Stefano Baroni wrote:

> Dear Xianghjun:
>
> the present version of PWscf cannot deal with spin spirals. An old 
> version of it actually did. You may want to get in touch with Ralph 
> Gebauer (rgebauer at ictp.trieste.it) for more details on the actual 
> availability of that old version. Even better, you may want to 
> volunteer and patch the routines for spirals contained in that old 
> version into the new one ;-) Some details that you may find 
> interesting (along with some nice ideas on magnon dynamics, 
> constrained DFT, etc.) are contained in Ralph's PhD thesis, available 
> on the web at URL www.cecam.fr
>
> Concerning J, the best way to calculate it is by constrained DFT. What 
> ought to be done is to calculate the energy difference between 
> configurations in which the magnetic moments on neighboring atoms are 
> constrained to different directions, and then fit the results to kind 
> of a Heisenberg model. Again, constrained DFT used to be implemented 
> in PWscf in the past, using the penalty function technique that is 
> described e.g. in Ralph's thesis. If it is no longer implemented, it 
> would be very easy to re-implement it.
>
> Hope this helps
> Yours, Stefano B
>
> On Oct 20, 2004, at 10:04 AM, xianghjun wrote:
>
>> xianghjun wrote:
>>
>>> Dear all:
>>>    I want to deal with the non-collinear magnetism systems using 
>>> pwnc.x,
>>> would you please recommend some references about the implementation 
>>> in PWNC?
>>> P.S.,  I want to get the exchange parameter J using PWNC, is that 
>>> possible?
>>>
>>>
>>> Best regards,
>>> xianghjun
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>>
>> An other related question is:
>> Can PWNC deal with spin spirals?
>> I have examined the input help file  "INPUT_NC",
>> it seems  that the answer is "no".
>> Am I right?
>> Best regards,
>> xianghjun
>>
>>
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>>
> ---
> Stefano Baroni    ---  SISSA  &  DEMOCRITOS National Simulation Center
> via Beirut 2-4 34014 Trieste Grignano / 
[+39] 040 3787 406 (tel) -528 
> (fax)
>
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> m

Thank Baroni and Ralph for helpful comments.
 I have downloaded Ralph's PhD thesis and have found that the thesis is 
very
interesting. If I could and if the developers have no such plans, I will 
be very happy to patch
the routines for spirals into the new PWSCF version.
Fortunately, I find that there are some input parameters to constrain  
the magnetic direction
in the INPUT_NC file. So the constrained DFT should be implemented in 
the present PWSCF version.

Best regards,
xianghjun