[Pw_forum] Problem in relaxing Si structure

Lorenzo Paulatto lorenzo.paulatto at impmc.upmc.fr
Tue May 5 11:09:31 CEST 2015

Dear Reza,
what does not converge? The single SCF step or the relax calculation?

Please not that you are not doing a relax calculation but a damped 
dynamic one. If your damped dynamics are not damped enough it will never 

Use ion_dynamics="bfgs" instead (which is the default, do not play with 
parameters if the default ones work)


I also notice that you are using a smearing to integrate the Fermi 
surface of Silicon, but Silicon is not a metal. If fore some mysterious 
reason you want to use a smearing you may need more k-point, but the 
calculation SCF should converge regardless.

On 04/05/15 23:42, reza vatan wrote:
> Dear users,
> I have been trying to perform "calculation=relax" on Si bulk structure
> generated by a super cell ( or unit cell) containing 8 atom repeating in
> a simple cubic lattice (ibrav=1). I created this super cell, by cutting
> a cell containing 8 atoms from perfect Si bulk structure obtained from
> experimental and theoretical results. The problem is that my calculation
> doesn't converge at all, although the structure seems to be relaxed. Is
> there any one here knows where the problem is. I attached the input file
> that I run.
> Best,
> Reza
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Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cx 05

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