[Pw_forum] About NON COLLINEAR magnetism

[Stefano Baroni]

Dear Xianghjun: welcome in the family of PWscf developers!
Hope you will enjoy - Stefano B.

On Oct 20, 2004, at 4:50 PM, xianghjun wrote:

> 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
>>>>
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>>>
>>>
>>> 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)
>>
>> Please, if possible, don't  send me MS Word or PowerPoint attachments
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>>
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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
>
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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)

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html