Dear Adriano Martins, if the SCF calculation is not converging, than you should reduce the mixing_beta parameter. I never performed calculations on your specific system, but for the Ni-X surfaces that I've studied I had to use a mixing_beta should equal to 0.05-0.4 in order to reach convergence.
I hope it helps, Fabio Negreiros Ribeiro IPCF - CNR Pisa, Italy -----Original Message----- From: martins <[email protected]> To: pw_forum <pw_forum at pwscf.org> Sent: Tue, Sep 13, 2011 9:28 pm Subject: [Pw_forum] Convergence problem with Ni/Ni3Al system Dear all, I'm studying the Ni/Ni3Al system. In order to estimate the value of the interface energy, I built several supercells keeping Nx = Ny = 1 (the Ni and Ni3Al lattice parameters are commensurated) and vary the number of unitary cells along the z direction, but constraining the numbers of Ni and Ni3Al cells to be equal. For small systems, nz = 2 and nz = 4, the calculations runned without any problem. However, for nz = 6 and nz = 8 I'm having problems of convergency: the quantum espresso is unable to reach the minimum value of energy. I tried several modifications: i) Increase ecutwfc and the k-point sampling; ii) Increase ecutrho; iii) Modify the ion and cell dynamics options; iv) ... Bellow I send the input file. I appeciate any help to solve this problem. If someone want to write me directly to my personal e-mail, fell free! One last information: I tried too to run only a SCF calculation... and the result not converged. Thanks in advance, Adriano Martins (Universidade Federal Fluminense - Brazil) -------------------- Typical Input File ------------------------------- &control calculation = 'vc-relax', restart_mode='from_scratch' prefix='NiNi3Al' tstress = .true. tprnfor = .true. pseudo_dir = '/home/martins/programas/espresso-4.3.2/pseudo/', outdir='/home/martins/calculos/QE/NiNi3Al/nx1ny1nz6/' / &system ibrav = 0, celldm(1) = 40.35, nat = 24, ntyp = 2, ecutwfc = 40.0, ecutrho = 320, nspin = 2, starting_magnetization(1) = 0.0, starting_magnetization(2) = 0.2, occupations = 'smearing', smearing = 'gaussian', degauss = 0.02, / &electrons diagonalization='david' mixing_mode = 'plain' mixing_beta = 0.70 conv_thr = 1.0d-6 / &ions ion_dynamics = 'bfgs' / &cell cell_dynamics = 'bfgs' cell_dofree = 'z' / CELL_PARAMETERS 0.16667 0.00000 0.00000 0.00000 0.16667 0.00000 0.00000 0.00000 1.00000 ATOMIC_SPECIES Al 26.981 Al.pbe-sp-van.UPF Ni 58.693 Ni.pbe-nd-rrkjus.UPF ATOMIC_POSITIONS alat Ni 0.00000 0.00000 0.00000 Ni 0.00000 0.08333 0.08333 Ni 0.08333 0.08333 0.00000 Ni 0.08333 0.00000 0.08333 Ni 0.00000 0.00000 0.16667 Ni 0.00000 0.08333 0.25000 Ni 0.08333 0.08333 0.16667 Ni 0.08333 0.00000 0.25000 Ni 0.00000 0.00000 0.33333 Ni 0.00000 0.08333 0.41667 Ni 0.08333 0.08333 0.33333 Ni 0.08333 0.00000 0.41667 Al 0.00000 0.00000 0.50000 Ni 0.00000 0.08333 0.58333 Ni 0.08333 0.08333 0.50000 Ni 0.08333 0.00000 0.58333 Al 0.00000 0.00000 0.66667 Ni 0.00000 0.08333 0.75000 Ni 0.08333 0.08333 0.66667 Ni 0.08333 0.00000 0.75000 Al 0.00000 0.00000 0.83333 Ni 0.00000 0.08333 0.91667 Ni 0.08333 0.08333 0.83333 Ni 0.08333 0.00000 0.91667 K_POINTS automatic 8 8 2 1 1 1 ---------------------------------------------------------------------- ------------------------------------ Adriano de Souza Martins Professor Adjunto III Departamento de F?sica - ICEx Polo Universit?rio de Volta Redonda Universidade Federal Fluminense ------------------------------------ ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program. _______________________________________________ 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/20110914/9edb0f40/attachment.htm
