[Pw_forum] Imposed symmetry

[Stefano Baroni]

On Feb 6, 2009, at 1:14 AM, Timothy Mason wrote:

>
> Dear Stefano,
>
>>> ii) some noise comes >in unporposedly, because of numerical  
>>> accuracy >>(this is often coped is, >again as suggested by  
>>> Gabriele, by explicitly >>>simmetrizing the resulting >forces),
>
> does this imply that a good fix to the checkallsym error in vc-relax  
> is to increase ecut to avoid numerical errors that would break the  
> symmetry during vc-relax?

I do not think so. I confess not to know what the "checkallsym error"  
is,  but any errors done by reducing the basis set cannot break any  
symmetry. I was rather referring to small roundoff errors that may  
accumulate during the computation.

Stefano

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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de la pensée - Jean Piaget

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