Dear Sir, Thank you very much for your kind guidance. I will do the exercise.
best regards Sagar ________________________________ Message: 6 Date: Thu, 25 Jun 2009 07:40:12 -0400 From: Nicola Marzari <[email protected]> Subject: Re: [Pw_forum] energy origin in espresso To: PWSCF Forum <pw_forum at pwscf.org> Message-ID: <4A43621C.8030509 at mit..edu> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Paolo Giannozzi wrote: >> then one have to use a common reference to compare >> the levels of different calculations. For this purpose one >> can use e.g. take a hydrogen molecule 10 ? away from >> the slab or molecule, whose bonding orbital can be taken >> as reference. > > yes, this is a simple way to find a common alignment Dear Ambavale, to elaborate on Paolo's comment: this is one of the two common ways to do it. The other would be to do a plot of the electrostatic potential - far away form the slab it will become flat (unless your slab, e.g., has a surface dipole - then you'll learn you have a small problem, and need to be careful about electrostatic interactions between different charges). But suppose it will become flat - that will point to the reference zero energy of that calculation. You redo this for all calculations, and you have reference points of each of them. Use this approach, and the one where you add the hydrogen molecule. Do they give you the same results ? In principle they should - if they do not, you need to figure out what is the problem, and in the process you learn a lot about accuracy. Warmly recommended, nicola -- --------------------------------------------------------------------- Prof Nicola Marzari Department of Materials Science and Engineering 13-5066 MIT 77 Massachusetts Avenue Cambridge MA 02139-4307 USA tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu ------------------------------ _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum End of Pw_forum Digest, Vol 24, Issue 55 **************************************** ICC World Twenty20 England '09 exclusively on YAHOO! CRICKET http://cricket.yahoo.com -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20090626/72b41acc/attachment.htm
