Dear all, Sorry, I did not spot that the pseudopotential used in the input file for the Workfunction calcultion has been a GGA pseudopotential. I am also sorry to use the word 'close' because I think 'compared' is much appropriate.
The difference between GGA and LDA for the workfunction calculation for pure metal surfaces is in the range of 0.2-0.3 eV (Table VI, PRB. 80, 235407 (2009)) Beside the LDA prediction of the workfunction calcultion for pure metal surfaces, my interest was on the mixing_mode (Three mixing_mode are available in QE) effect on the calculated workfunction. After reading, consulting and testing the three type of mixing it seems that the mixing method has no effect on the workfunction results. Could someone comment please in case of the mixing_mode has an effect on the workfunction results? Best regards, A. Kachmar > Date: Mon, 15 Apr 2013 14:15:11 +0200 > From: Ari.P.Seitsonen at iki.fi > To: pw_forum at pwscf.org > Subject: Re: [Pw_forum] Two vacuum energies with dipole correction > > > Dear Niharika Joshi, > > My quick answer, the relaxed surface is more realistic, that's why I > would take the value at that side. > > Regarding the comment about "something close to the experimental value" > of the work function, it is known that the absolute value of the clean > surfaces are often of the order of 0.5 eV wrong (too low, if I remember > correctly) with the GGA functionals compared to the experimental values: > One of the famous short-comings of these functionals; funnily enough LDA > is often closer to the experiments, if I remember correctly. > > Greetings from Zurich, > > apsi > > -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=- > Ari P Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/ > Physikalisch-Chemisches Institut der Universitaet Zuerich > Tel: +41 44 63 54 497 / Mobile: +41 79 71 90 935 > > > On Mon, 15 Apr 2013, N H Joshi wrote: > > > Dear Ali, > > > > Thanks a lot for your reply. > > > > The work function value that I get without the dipole correction is 4.9 eV > > and the with dipole correction I get 5 eV and 4.8 eV if I take lower and > > higher potential value > > in the vacuum region. > > > > And I couldn't follow what you meant by 'without mixing_mode'. > > Won't the code take the default mixing_mode? And how does it help in this > > case? > > > > With regards, > > Niharika Joshi > > Project student, > > Department of Physics, > > IISER, Pune > > India. > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20130417/e6f95735/attachment.html
