Dear Prasenjit and Nicola, Thank you for the comment on smearing. I was not paying attention to it. A quick look on some logs I have here show that this contribution is not that much negligible in some calculations (around 0.00364895 Ry, for example). Thus I'll evaluate the total energy as "! total energy - smearing contribution(-TS)" from now on and see what I get.
I'm finishing a test battery based on another suggestion from the forum. Once I report it, I'll take the best result from there and experiment with smearing to see what we get from it. Thanks again! Giovani 2011/2/15 Nicola Marzari <nicola.marzari at materials.ox.ac.uk> > > > Thanks Prasenjit - a further comment, to be careful about. > > In molecules/clusters, you could end up with a situation where > the HOMO is degenerate, and you have fractional occupations, > so the entropy term S is constant, and -TS is linear (T is deguass); > this supposing the other states below the homo are separated > from the HOMO by at least 2 or 3 times degauss. > > What you want is the total energy - that is obtained by > subtracting the term "-TS" to the "total energy" printed > by the code (since the "total energy" printed by the code, > when you use a smearing, is not the total energy, but the > total free energy E-TS). > > nicola > > > > On 2/14/11 5:22 AM, Prasenjit Ghosh wrote: > > A small suggestion, try changing the smearing type, instead of using > > mp, try using m-v or even simple gaussian is fine for small clusters. > > Also, you should check the value of the contribution to total energy > > from smearing (printed in the output after your calculations have > > converged).......ideally for small clusters as yours, this should be > > zero. This tells you that your smearing is physically small enough so > > that the spurious effect of broadening becomes negligible. > > > > With regards, > > > > Prasenjit > > > > > -- > ---------------------------------------------------------------------- > 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 > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Giovani -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110215/f91a0db6/attachment-0001.htm
