[Pw_forum] big atomic forces

[Stefano Baroni]

PPS: sorry for the improbable English of my previous message ...
S.

On Jun 4, 2007, at 8:06 PM, Stefano Baroni wrote:

> Others may have better answers than me, but ...
>
> 1) I do not know how forces are calculated with tetrahedra, but I  
> think fear that the total energy calculated with tetrahedra is not  
> variations, so that Helmann Feynman forces may have some problems ...
>
> 2) Not that a force of 1d-3 is that large after all ...
>
> As said, other answers may be more illuminating than mine.
>
> Stefano
>
> On Jun 4, 2007, at 7:24 PM, Jess Kondor wrote:
>
>>
>> Hello, everybody,
>>
>>  I have a question. I relaxed a surface using 8x8x1 k-point mesh  
>> and 'm-v' smearing method with degauss=0.01 with criteria for  
>> forces 4.d-4 . Then I performed 'scf' calculation with increased  
>> number of k-points (12x12x1) and turn on an option 'tprnfor  
>> = .true.' in order to calculate forces. Forces are OK (all lower  
>> than 4.d-4). But when I perform 'scf' with occupation method  
>> 'tetrahedra'  (other parameters are the same), forces on atoms are  
>> much higher (some of them are ~2.0d-3). Does it mean that geometry  
>> relaxation is not been completed?
>>
>> cheers,
>>    Jess
>>
>
> ---
> Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
> Trieste
> [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)
>
> Please, if possible, don't  send me MS Word or PowerPoint attachments
> Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html
>
>
>

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html



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