Dear Nicola Thanks for the recommendations! Regards Ricardo -------------------------------------------- Dr. Ricardo Faccio Prof. Adj. de F?sica
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 08:19, Nicola Marzari <nicola.marzari at materials.ox.ac.uk > escribi?: > On 1/20/11 2:26 AM, 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 Jos?. 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 > > > Dear Ricardo, > > two options, I think - the simplest is that a nscf calculation, > dealing with one k-point at a time, would not really require more > RAM, but for the fact that k-points different from gamma have > complex wavefunctions (so indeed you might be out of luck). > > Another possibility would be to calculate the Wannier functions > for this system, and then use Wannier interpolation (see our 2005 > PRL Lee et al.). This can work extremely well, but it requires > learning > a new code. > > As a side note, the CP codes requires much less memory than PWSCF - > it has only gamma sampling, though. It does deal with metals, using > the "ensemble-DFT" approach, but that has not been optimized as much > as the other parts. Worth trying, though! > > A last resort would be to decrease the thickness of your slab - (111) > surfaces could be ok with as little as 3 layers, or maybe even 2 > (maybe you could put a few more atoms in the 3rd layer below the > cobalt). > > nicola > > > > -- > ---------------------------------------------------------------------- > Prof Nicola Marzari Department of Materials University of Oxford > Chair of Materials Modelling Director, Materials Modelling Laboratory > nicola.marzari at materials.ox.ac.uk http://mml.materials.ox.ac.uk/NM
