Increase the number of k-points in the kz direction. Since you are dealing with an fcc, you should have something like 12x12x12 to have a reasonable description of a bulk structure. Other than that, I see no other errors in the input. Well, the cutoffs are kind of exagerated in my perspective given that you have a USPP, but depending on what you plan to do later, this could be right. And a too high cutoff is not an error, only a waste of time.
I hope that helps. Fabio Negreiros -----Original Message----- From: Krukau, Aliaksandr <[email protected]> To: pw_forum at pwscf.org Sent: Wed, Mar 2, 2011 11:58 pm Subject: [Pw_forum] Lattice constant for copper Dear QE users, I apologize if my question seems stupid to you. I am a complete QE newbie and could not find any answer in the tutorials. I am trying to find equilibrium lattice constant for copper with PBE and ultrasoft pseudopotentials. I ran scf calculations for face-centered cubic unit cell for a number of lattice constants: Lattice constant 6.65 a.u. ! total energy = -121.62734203 Ry Lattice constant 6.66 a.u. ! total energy = -121.62735421 Ry Lattice constant 6.67 a.u. ! total energy = -121.62734651 Ry Lattice constant 6.65 a.u. ! total energy = -121.62731956 Ry The minimum total energy is for the lattice constant 6.66 a.u. But this value drastically differs from the published PBE value of 6.86 a.u. (Phys. Rev. B, vol. 77, 05414 (2008), Table II). It also differs from the experimental value of 6.83 a.u. I attach the input file that I used for lattice constant 6.66 a.u. below the signature. Why is equilibrium lattice constant so low? Best regards, Alex Krukau, Indiana University ------------------------------------------------------ &control calculation='scf' pseudo_dir = '~/espresso-4.2.1/pseudo/ADDITIONAL', / &system ibrav = 2, celldm(1) = 6.66, nat= 1, ntyp= 1, ecutwfc = 120.0, ecutrho = 1000.0 occupations='smearing', smearing='marzari-vanderbilt', degauss=0.01 / &electrons conv_thr=0.0000001 / ATOMIC_SPECIES Cu 63.546 Cu.pbe-n-van_ak.UPF ATOMIC_POSITIONS Cu 0.0 0.0 0.0 1 1 1 K_POINTS automatic 12 12 1 0 0 0 _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110302/56e1273d/attachment.htm
