[Wien] Problem with force minimization

[Saeed Bahramy]

Dear Maxim,

Yes I reduced the default RMT's  by 2%. I'm now changing the step  
sizes in case.inM, but so far no success!
Any way, I appreciate your kind advices

Sincerely,
Saeed


On Oct 26, 2010, at 5:58 PM, Maxim Rakitin wrote:

> 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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