[Pw_forum] big calculations II

[Ricardo Faccio]

Dear Giuseppe
Regarding the first part, I know that i have a near optimized  
structure, since it was fully optimized by SIESTA. Now, I want to  
perform some DFT+U calculations with espresso....
Regarding your last recomendation.... It is always on my mind, but it  
is not so easy  :-)
Thanks!
Regards
Ricardo

--------------------------------------------
Dr. Ricardo Faccio
Prof. Adj. de Física

Av. Gral. Flores 2124. CC 1157. CP 11800.
Phone: + 598 2 924 9859
Fax: + 598 2 924 1906
Web: http://cryssmat.fq.edu.uy/ricardo/ricardo.htm
---------------------------------------------

El 20/01/2011, a las 03:43, Giuseppe Mattioli <giuseppe.mattioli at mlib.ism.cnr.it 
 > escribió:

>
>> to your recent PRL). I optimized the structure with gamma point with
>> 25 and 250 ecut and rhocut respectively
>
> Only a little suggestion (I've performed some similar calculations):  
> I suppose
> that your Co pseudopotential is quite far from convergence at 25  
> Ry... If
> your calculation of the isolated molecule at gamma is converged at  
> 25 Ry
> PLEASE SHARE THE PSEUDOPOTENTIAL...:-) !!!! I suppose also that forces
> calculated by using a higher pw cutoff and a well converged k-point  
> mesh on
> the gamma/25 Ry geometry (molecule+surface, of course) will be still  
> quite
> high. Perhaps you should consider to migrate your calculation to a  
> better
> machine...
> HTH
>
> Yours
>
> Giuseppe Mattioli
>
>
> On Thursday 20 January 2011 03:26:27 Ricardo Faccio wrote:
>> Dear nicola
>> Thanks gr your email, i would like to take the opportunity and ask  
>> you
>> a further question. I have a similar situation than José. I'm work 
>> ing
>> with a cobalt porphyrin deposited over a metallic substrate (similar
>> to your recent PRL). I optimized the structure with gamma point with
>> 25 and 250 ecut and rhocut respectively. It takes almost the 100% of
>> my 8Gb RAM quad core computer. Now i want to get a reasonably DOS fir
>> this system, but i need more k-points, and thus I will need more RAM
>> memory. Would you recommend anything else for getting a good DOS for
>> my quad core 8 GB RAM machine?
>> Thank you in advance.
>> Ricardo
>>
>> --------------------------------------------
>> Dr. Ricardo Faccio
>> Prof. Adj. de Física
>>
>> Av. Gral. Flores 2124. CC 1157. CP 11800.
>> Phone: + 598 2 924 9859
>> Fax: + 598 2 924 1906
>> Web: http://cryssmat.fq.edu.uy/ricardo/ricardo.htm
>> ---------------------------------------------
>>
>> El 19/01/2011, a las 21:54, Nicola Marzari
>> <nicola.marzari at materials.ox.ac.uk
>>
>>> escribió:
>>>
>>> Given your system size, it's likely that gamma point
>>> is good enough - a full relaxation with 18 Ry cutoff and
>>> the gamma point would bring you very very close to the correct
>>> result.
>>>
>>> Then, try 30 Ry and Gamma point - do the results change a lot ?
>>> Probably note, and maybe 25 Ry is enough (there are tests of
>>> the C ultrasoft on the pseudopotential page). I'd assume a dual of
>>> 8, i.e. a cutoff for the charge density of 8 times the cutoff on the
>>> w