[Wien] Problem with force minimization

[Saeed Bahramy]

Dear Maxim,

Thanks for your prompt reply. Actually I get no error. My problem is  
that force values  do not converge to what I want (1 mRy/a.u). I have  
a hexagonal unit cell containing 6 atoms. The x and y coordinates are  
at hight symmetry points (1/3 and 2/3) so basically the force values  
along x and y are zero.  Due to the same reason, the program itself  
freezes the atomic x and y positions in case.inM.

I have no problem with scf-calculation. I invoke the command "run_lapw  
-I -ec 0.00001 -fc 1.0 -i 40" and after few iterations, I get what I  
expect. So far so good. The problem starts when I want to optimize the  
atomic positions. As I mentioned it doesn' matter what scheme I choose  
in case.inM (PORT, NEW1 or NEWT), for the first few steps, The force  
values decrease, but then they remain unchanged.

I have already read the tutorial which you linked it for me, but it  
just gives some general idea how to do force minimization using WIEN2K.

Sincerely,
Saeed


On Oct 26, 2010, at 4:58 PM, Maxim Rakitin wrote:

> Dear Saeed,
>
> What system do you investigate? Did you perform scf-calculation  
> without minimization? Was it successful?
>
> Which errors did you get during minimization? In case you need to  
> minimize forces along the z-axis only, you can "freeze" atom  
> positions in case.inM file. There is a nice manual on structure  
> optimization here: http://www.wien2k.at/reg_user/textbooks/Optimization-Notes.pdf 
> . You can find all answers on your question in the document.
>
> Best regards,
> - Maxim Rakitin
>
>
> 26.10.2010 13:36, Saeed Bahramy пишет:
>> Dear all,
>>
>> I'm trying to do force minimization using WIEN2K. I've tried  
>> different schemes including PORT, NEW1 and NEWT, with different  
>> step sizes for ionic movements, but none of them has worked so far.  
>> Regardless of them method I use, the forces reach to certain values  
>> after few steps and then remain unchnaged (better to say that they  
>> tends to oscillate around some certain values). My system is rather  
>> simple and due to symmetry consideration, the force values need to  
>> be minimized only along the z axis.
>>
>> For minimization, I use the command: min_lapw -j "run_lapw -I -fc  
>> 1. -ec 0.00001 -i 40"
>>
>> Could somebody tell me what I need to add or change in my command  
>> line or in the input files, in order to optimize the atomic  
>> positions.
>>
>> Your help is greatly appreciated,
>> Sincerely,
>> S. Bahramy
>>
>>
>>
>>
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>>
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