[Wien] Problem with force minimization

[Saeed Bahramy]

Dear Maxim,

It is around 15 mRy/a.u. on each atom. In my case.inM I've set the  
force criterion to 1.0 mRy/a.u..

I guess the atomic positions are very close to the optimal ones, but  
probably my trial steps are rather large ....

Sincerely,
Saeeed


On Oct 26, 2010, at 5:27 PM, Maxim Rakitin wrote:

> Dear Saeed,
>
> What is the maximum value of forces in your calculations now? By  
> default, minimization stops when the forces are less than 2.0 mRy/ 
> a.u. (case.inM file, the first line, the second field), if you  
> didn't change it for less value.
>
> Best regards,
> - Maxim Rakitin
>
>
> 26.10.2010 14:17, Saeed Bahramy пишет:
>> 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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