I reproduce here the answer I gave privately ... just not to let a thread without reply in the forum...
Dear Xinzheng Li, the "total energy" should be the right number to look at... it is actually: one-electron contribution + hartree contribution + xc contribution + ewald contribution - Fock energy 1 + Half Fock energy 2 In the Harris Foulkes estimate the Fock energyes are not properly accounted... I'll correct this information. Thank you for the report. regards, stefano xinzheng li wrote: > Dear friends, > > My name is Xinzheng Li. I am a postdoc in University College London. I > am using PWSCF to perform some PBE0 calculations for water cluster on > metal surface recently. In order to make sure that the PBE0 number I got > from PWSCF is correct. I performed a test for the binding energy of a > water-dimer in gas phase (total energy of 2 water moleculars minus the > total energy of a water dimer) taking the all-electron PBE0 results from > Gaussian03 as reference. The converged binding energy from Gaussian03 > is around 207 meV. While after PBE0 calculation of PWSCF is performed, I > have these lines in the output file: > > ! total energy = -68.48225787 Ry > Harris-Foulkes estimate = -72.38797788 Ry > estimated scf accuracy < 0.00000008 Ry > > The total energy is the sum of the following terms: > > one-electron contribution = -144.72933450 Ry > hartree contribution = 71.54274579 Ry > xc contribution = -12.87564636 Ry > ewald contribution = 13.67425725 Ry > Fock energy 1 = -7.81160613 Ry > Fock energy 2 = -7.81177236 Ry > Half Fock energy 2 = -3.90588618 Ry > > I have two questions about this output: > > 1. Shall I take the '! total energy' as the final total energy, or the > 'Harris-Foulkes estimate' as the final total energy? For the comment: > 'The total energy is the sum of the following terms', if I sum the > numbers below, I don't get either 'Harris-Foulkes estimeate', or '! > total energy'. Only if I sum the one-electron contribution, hartree > contibution, xc contribution and the ewald contribution, can I get the > 'Harris-Foulkes estimate'. Does it mean that I should take > 'Harris-Foulkes estimate' as the final energy? If so, what is the > meaning of the '! total energy'? > > 3. If I take Harris-Foulke estimate' as the total energy, the binding > energy I get is 184 meV. If I take '! total energy' as total energy, the > binding energy is 158 meV. Both of these two number are > 20 meV from > the Gaussian all-electron benchmark. What is the expectation for the > accuracy of such a value in the PWSCF code compared with all-electron > Gaussian (when pseudopotentials, and supercell-size convergence are > well-tested)? > > Thanks a lot for your patiency in advance! > > Sincere > Xinzheng > > > > ----------------------------------------------------------------- > Dr. Xinzheng Li > London Centre for Nanotechnology, University College London > 17-19 Gordon Street, London WC1H, 0AH > ucanxli at ucl.ac.uk > ------------------------------------------------------------------ > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
