[Wien] Problem with force minimization

[Maxim Rakitin]

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
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>>
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>