# [Octopus-devel] stupid bug?

alberto.castro at tddft.org alberto.castro at tddft.org
Fri Mar 7 14:39:56 WET 2008

```Hi,

I guess you mean abs_dens = int( |rho_i - rho_o| ).

And yes, it seems that we do not convert the units. I would be in favour
of making use of dimensionless definitions whenever possible, so moving to
what you suggest.

And what about simplifying a bit, getting rid of the "absolute"
convergenge criteria?

But there is one point little about the eigenvalues criterion:

abs_ev = sum( |ev_i - ev_o| )
rel_ev = abs_ev / |sum(ev_o)|

Shouldn't we have rel_ev = abs_ev / sum(|ev_o|) ?

(The sum of the absolute values of the eigenvalues, and not the absolute
value of the sum)

Cheers, Al.

On Fri, 7 Mar 2008, Miguel Marques wrote:

>   Hi everyone,
>
>   I think I discovered a (serious and stupid) bug. It has to do with the
> units in the stopping parameters of the SCF. It is very easy to solve,
> but we have to decide what is the right way of doing it. Let me explain:
>
> abs_den = int( (rho_i - rho_o)^2 )
> therefore, it has units of length^-3
>
> rel_den = 1/N abs_den
> again, units of length^-3
>
> abs_ev = sum( |ev_i - ev_o| )
> units of energy
>
> rel_ev = abs_ev / sum(ev_o)
> dimensionless
>
> abs_forces
> units of force
>
> rel_forces
> dimensionless
>
> To my surprise I found that in octopus we do not convert the inputs of
> these variables, i.e., we are effectively using atomic units for all of
> them (someone can check it independently?)!!!! To change that is
> trivial, of course, but I also believe that the definition of abs_den is
> a bit weird. Wouldn't it be better:
>
> abs_den = int( |rho_i - rho_o|^2 )
>
> This definition is dimensionless, and I don't see why it should be worse
> than the previous one.
>
> In any case, I guess that a lot of tests will change due to the
> different stopping criterion... Let me know what you think is best to do...
>
>   cheers,
>   Miguel
>
> --
> Dr. Miguel A. L. Marques
> marques at tddft.org
>
> Laboratoire de Physique de la Matière Condensée et Nanostructures
> (LPMCN) - Université Lyon I
> Bâtiment Brillouin, Domaine scientifique de la DOUA
> 69622 Villeurbanne Cedex
> Tel +33 (0)4 72448187
> Fax +33 (0)4 72432648
> _______________________________________________
> Octopus-devel mailing list
> Octopus-devel at tddft.org
> http://www.tddft.org/mailman/listinfo/octopus-devel
>

======================================================================
Dr. Alberto Castro

Institut fur Theoretisch Physik, Freie Universitat Berlin.
Arnimallee, 14, Berlin 14195 (Deutschland)

Tel:   +49 30 83853028
Fax:   +49 30 83855258
skype: alberto_c_barrigon
email: alberto at physik.fu-berlin.de
======================================================================

```