[Pw_forum] Problem with convergence parameters forc_conv_thr and etot_conv_thr

[Giuseppe Mattioli]

Dear Gabriel

> to run an optimization of one crystal system using the keyword ‘wc-relax’.

I suppose you are performing a "vc-relax" calculation instead of a "wc-relax" one, which could be 
something more exotic... You are trying to optimize the lattice parameters of your crystal; some 
additional convergence criteria should be satisfied (e.g., some target pressure...). You may try first 
a simple "relax" calculation, if you want to perform a "fast&clean" run.

HTH

Giuseppe
 
On Tuesday 19 June 2012 06:27:03 Gabriel Pagola wrote:
> Dear all,
> I am trying
> to run an optimization of one crystal system using the keyword ‘wc-relax’.
>  
> I used the
> following values as convergence parameters:
>  
>     forc_conv_thr
> = 3.D-2
>     etot_conv_thr=5.0D-1
>  
> I have put
> very “high” values in order to be sure that the calculations finish in a
> few iterations. But, as you can see in the output attached, the QE
> continues making iterations although the conditions of convergence are
> clearly fulfilled. For example
> seeing the total energy in first iterations:
>  
> !    total energy              =   -1159.31135867 Ry
> !    total energy              =   -1158.59596269 Ry
> !    total energy              =   -1160.05552255 Ry
> !    total energy              =   -1159.98617122 Ry
> !    total energy              =   -1160.17541568 Ry
> !    total energy              =   -1160.14018816 Ry
> !    total energy              =   -1160.22211554 Ry
> !    total energy              =   -1160.22852050 Ry
> !    total energy              =   -1160.23360361 Ry
> !    total energy              =   -1160.23596633 Ry
>  
> The parameter
> of convergence etot_conv_thr has been fulfilled since the 7th or the 8th
> iteration. The same has happened with the force an forc_conv_thr
>  
> I don’t
> know why this happens. Perhaps I have misunderstood the manual of QE.
>  
> I have
> attached the entire input and output
>  
> Any help
> would be appreciated.  Thank in advance
> Gabriel Pagola   
> 
> Physics Department
> FCE. y N, Universidad de Buenos Aires
> (1428)Ciudad Universitaria-Pab. I

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   Giuseppe Mattioli                            
   CNR - ISTITUTO DI STRUTTURA DELLA MATERIA   
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