[Pw_forum] big calculations II

[Ricardo Faccio]

Thanks Paolo, I will try it.
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 06:30, Paolo Giannozzi <giannozz at democritos.it>  
escribió:

>
> On Jan 20, 2011, at 3:26 , Ricardo Faccio wrote:
>
>> 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?
>
> "more k-points" does not imply more memory:  the code needs to
> keep in memory the Kohn-Sham orbitals for a single k-point only.
> This implies a large amount of I/O, though. Note that the size of KS
> orbitals for Gamma-only calculations is half the size of the same KS
> orbitals for a generic k-point, though, so if you are already at the
> limit
> with Gamma only, you may run out of memory with generic k-point.
>
> There are a few indications in the user guide on how to reduce the
> memory usage to the strict minimum. You could use conjugate-gradient
> diagonalization ('cg': slow). If you use Davidson (derault), reduce
> diago_david_ndim to 2. For scf calculations, reduce mixing_ndim
> to 4 or so.
>
> P.
> ---
> Paolo Giannozzi, Dept of Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
>
>
>
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