Perhaps Kenvin refers to cohesive energy. If you know exactly what you want to calculate, you will be able to calculate. So please make sure you understand the quantity. -------------------------------------------------- Duy Le PhD Student Department of Physics University of Central Florida.
"Men don't need hand to do things" On Thu, Feb 4, 2010 at 8:53 AM, Gabriele Sclauzero <sclauzer at sissa.it> wrote: > Dear Kelvin, > > ? please make a serious effort to include in your responses only relevant > emails: > replying to digests is quite not a good idea... I had to scroll hundreds of > lines before > getting to the right point. > > >> ? ? Message: 4 >> ? ? Date: Thu, 04 Feb 2010 09:08:41 +0100 >> ? ? From: Gabriele Sclauzero <sclauzer at sissa.it <mailto:sclauzer at >> sissa.it>> >> ? ? Subject: Re: [Pw_forum] how to conver to unit of eV/atom in supercell? >> ? ? To: PWSCF Forum <pw_forum at pwscf.org <mailto:pw_forum at pwscf.org>> >> ? ? Message-ID: <4B6A8089.9080009 at sissa.it >> ? ? <mailto:4B6A8089.9080009 at sissa.it>> >> ? ? Content-Type: text/plain; charset=ISO-8859-1; format=flowed >> >> >> >> ? ? Wong Kelvin wrote: >> ? ? ?> Dear all >> ? ? ?> >> ? ? ?> when i calculate a single atomc Cu primitive cell, the energy is >> ? ? ~ -87 >> >> ? ? What are you trying to compute? An isolated atom or a bulk phase? In >> ? ? any case, if you are >> ? ? using pseudopotentials the total energy has not any physical meaning >> ? ? by itself. What is >> ? ? physically relevant are energy differences. >> >> ? ? ?> Ry. How to convert it to the eV/atom which normally is around >> ? ? -3.7 eV? >> >> ? ? Where did you get this value of -3.7 and what does it actually refer >> ? ? to? I mean, to which >> ? ? physical quantity? >> >> >> ? ? GS >> ? ? ?> Thanks >> ? ? ?> Wong >> ? ? ?> >> ? ? ?> >> ? ? o ------------------------------------------------ o >> ? ? | Gabriele Sclauzero, PhD Student ? ? ? ? ? ? ? ? ?| >> ? ? | c/o: ? SISSA & CNR-INFM Democritos, ? ? ? ? ? ? ?| >> ? ? | ? ? ? ?via Beirut 2-4, 34014 Trieste (Italy) ? ? | >> ? ? | email: sclauzer at sissa.it <mailto:sclauzer at sissa.it> >> ? ? ? ? ? ? ? | >> ? ? | phone: +39 040 3787 511 ? ? ? ? ? ? ? ? ? ? ? ? ?| >> ? ? | skype: gurlonotturno ? ? ? ? ? ? ? ? ? ? ? ? ? ? | >> ? ? o ------------------------------------------------ o >> >> Dear Gabriele >> Thanks for reply! >> >> I am trying to calculate the grain and twin boundary energies in metals. > > I don't think that any code can give this energies with a single total energy > calculation. > You have first to learn the general methodology to build these quantities. > >> I partially understand that absolute energy in pseudopotential >> calculation does not provide meaningful interpretation. > > If you are dealing with a bulk phase it's not only a matter of > pseudopotential, since you > are considering an infinitely extended solid. > On the other hand, all electron energies of an isolated atom, if studied in a > large enough > supercell, I think they would have a physical meaning. > >> The reported energies in literature for copper with PP calculations use >> to be around -3.7 eV/atom. Is there anything significant abt this >> figure? and i do not understand how to get it. simple by diving the >> total energy calculated by number of atom in supercell? if it is so, the > > Although I never did such kind of calculations, I don't believe that it's so > simple to get > that number. You should learn this from some textbook or lecture notes, > rather than from > this forum (which should treat more technical issues). Maybe if you are lucky > some user > with more experience on this will give you advice. > > > GS > >> value (~3.7) is way too small as compare to the 87 Ry for one copper >> atom primitive cell. >> >> regards >> Kelvin >> > > -- > > > o ------------------------------------------------ o > | Gabriele Sclauzero, PhD Student ? ? ? ? ? ? ? ? ?| > | c/o: ? SISSA & CNR-INFM Democritos, ? ? ? ? ? ? ?| > | ? ? ? ?via Beirut 2-4, 34014 Trieste (Italy) ? ? | > | email: sclauzer at sissa.it ? ? ? ? ? ? ? ? ? ? ? ? | > | phone: +39 040 3787 511 ? ? ? ? ? ? ? ? ? ? ? ? ?| > | skype: gurlonotturno ? ? ? ? ? ? ? ? ? ? ? ? ? ? | > o ------------------------------------------------ o > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
