Dear Giuseppe and Stefano, Thank you so much for your reply. I guess I have to rephrase my problem and think about it in a different way.
Best regards Nam > On Feb 23, 2021, at 8:22 PM, Giuseppe Mattioli <[email protected]> > wrote: > > > Dear Nam > If you forget the DFT problem of unbound electrons in anions (which is not a > chemical or physical problem) and think about the chemistry, there is no real > process that ends with a nitrate anion in gas phase, AFAIK. Desorption may > rather involve a neutral NO2 molecule, depending on the surface redox > chemistry. Of course release of anions in solution is possible, but you > should simulate a (proper or implicit) solvation environment. > HTH > Giuseppe > > Quoting Stefano Baroni <[email protected]>: > >> If the anion stays charged, which is an issue by itself in DFT, the distance >> will never be large enough, because the slab will generate a macroscopic >> electric field. sb >> >> ___ >> Stefano Baroni, Trieste -- http://stefano.baroni.me >> >>>> On 23 Feb 2021, at 07:05, Nam Tran <[email protected]> wrote: >>> >>> >>> Dear QE users, >>> >>> I would like to calculate the adsorption energy of a negative anion NO3- >>> with a positive slab (The total system is neutral). I cannot use the >>> convention formula Eds = E(slab+anion) - E(slab) - E(anion) because of the >>> charge compensation when calculating the energy of charged slab and charge >>> adsorbate. >>> >>> As the total system (slab+anion) is neutral, I wonder if it is possible to >>> just move the molecule far away from the slab (make sure that vacuum in >>> z-direction is large enough), and calculate the energy difference i.e., one >>> of them the molecule is far away from the surface and in the other one the >>> molecule adsorbed on the surface. >>> >>> >>> Best regards >>> Nam >>> >>> _______________________________________________ >>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu) >>> users mailing list [email protected] >>> https://lists.quantum-espresso.org/mailman/listinfo/users > > > > GIUSEPPE MATTIOLI > CNR - ISTITUTO DI STRUTTURA DELLA MATERIA > Via Salaria Km 29,300 - C.P. 10 > I-00015 - Monterotondo Scalo (RM) > Mob (*preferred*) +39 373 7305625 > Tel + 39 06 90672342 - Fax +39 06 90672316 > E-mail: <[email protected]> > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
