Dear Mourad > How to obtain the total energy E(Zn) and E(O2) ?
E(Zn) = total energy of a Zn(hcp) unit cell. You have to perform this calculation. E(O2) = an O2 molecule in an adequately large cubic supercell. You have to perform this calculation. Giuseppe On Tuesday 19 June 2012 14:10:42 debbichi mourad wrote: > Thank you Giuseppe. > How to obtain the total energy E(Zn) and E(O2) ? > > > > DEBBICHI Mourad > Unit? de Recherche Physique des Solides,99/UR/13-19, > D?partement de Physique, Facult? des Science de Monastir, > Avenue de l'Environnement 5019, Monastir Tunisie. > t?l:+21697487042 > mourad_fsm at yahoo.fr > > > ________________________________ > De : Giuseppe Mattioli <giuseppe.mattioli at ism.cnr.it> > ? : debbichi mourad <mourad_fsm at yahoo.fr>; PWSCF Forum <pw_forum at > pwscf.org> > Envoy? le : Mardi 19 juin 2012 12h27 > Objet : Re: [Pw_forum] (no subject) > > > Dear Mourad > No special keywords, only a bit of physical chemistry... > Let us suppose we are calculating The formation heat (aka formation > enthalpy, DeltaH_f) of wurtzite ZnO. First of all, what is it the > formation enthalpy? Suppose that we are not very rigorous, we may say "the > energy gained to form ZnO from Zn and O in their standard state". We may > consider therefore this chemical process: > > Zn(metal)+O2(gas)-->ZnO(wurtzite) > > How can we calculate such an energy? Well, all chemical "Delta" quantities > are defined as a difference between some final state quantity (free > energy, enthalpy, ...) and the related initial state quantity. If we > consider negligible the PV contribution to the above chemical process (H = > U+PV), we can estimate formation heats as differences of total energies > calculated in supercells: > > DeltaH_f (ZnO) = E(ZnO) - E(Zn) - E(O2) > > You must only be sure that the number of atoms in all the supercells is > fully consistent with your calculation: > > ZnO(wurtzite): 4 atoms (2 ZnO units) > Zn(metal, hcp): 1 atom > O2 molecule: 2 atoms > > Your final equation is therefore > > DeltaH_f (ZnO) = E(ZnO) - 2*E(Zn) - E(O2) > > Modify it according to your purpose... > > HTH > > Giuseppe > > On Tuesday 19 June 2012 11:21:54 debbichi mourad wrote: > > Dear pwscf users. > > How to calculate the formation enthalpy, which command I can added to > > the input? best regards > > > > > > > > DEBBICHI Mourad > > Unit? de Recherche Physique des Solides,99/UR/13-19, > > D?partement de Physique, Facult? des Science de Monastir, > > Avenue de l'Environnement 5019, Monastir Tunisie. > > t?l:+21697487042 > > mourad_fsm at yahoo.fr -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et ?gaux en droits. Les distinctions sociales ne peuvent ?tre fond?es que sur l'utilit? commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la libert?, la propri?t?, la s?ret? et la r?sistance ? l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <giuseppe.mattioli at ism.cnr.it>