[Wien] Problem with force minimization

[Maxim Rakitin]

Dear Saeed,

I think you are right, try to decrease steps in case.inM file. Did you 
reduce Rmt of atoms in your system? It's recommended to do that in case 
of optimization.

Best regards,
- Maxim Rakitin


26.10.2010 14:40, Saeed Bahramy пишет:
> 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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