For an el-ph calculation you need the same grid for the (electronic) k and (vibrational) q points, but the q points can be safely obtained from a coarse grid (4x4x2 or 8x8x2) using Fourier interpolation (q2r+matdyn).
On the other hand, the phonons on this coarse grid require 32x32x4 electronic k-points to be well converged. So: compute a coarse grid of phonon q-points with a fine grid of k-points, then interpolate the coarse grid to the fine grid and do el-ph with that. On Wednesday, 25 May 2016 19:47:21 CEST Paolo Giannozzi wrote: > Are you sure you need that many k-points and such a big cell in the z > direction? > Attached a quick-and-dirty test. Parameters are likely far from yielding > converged values, but it takes 50' on a single processor of my 2007 vintage > PC. Before starting a full-fledged calculation at convergence, you should > experiment a bit. Also, tuning the parallelism may make a significant > difference. > > Paolo > > On Wed, May 25, 2016 at 5:13 PM, Abualnaja, Faris < > > [email protected]> wrote: > > Dear all, > > > > > > I am running phonon calculations on graphene, and the calculations are > > taking days to complete! The calculations are run on a supercomputer and > > are running in parallel. I am using QE version 4.3.1, the amount of > > k-points that are calculated are 12x12x1 for an MP-grid which reduces down > > to 19 irreducible symmetry points. My phonon input is below: > > > > > > Phonon Dispersion of graphene > > > > &inputph > > > > recover=.true. > > > > tr2_ph=1.0d-16 > > > > ldisp=.true. > > > > nq1=12 nq2=12 nq3=1 > > > > prefix='graphene' > > > > amass(1)=12.01 > > > > fildyn='graphene.dyn' > > > > / > > > > and part of the output is shown here: > > > > > > Parallel version (MPI), running on 48 processors > > > > K-points division: npool = 3 > > > > R & G space division: proc/pool = 16 > > > > Computing dynamical matrix for > > > > q = ( 0.0000000 0.0000000 0.0000000 ) > > > > 25 Sym.Ops. (with q -> -q+G ) > > > > G cutoff = 245.0079 ( 16214 G-vectors) FFT grid: ( 32, 32,600) > > > > number of k points= 217 Methfessel-Paxton smearing, width (Ry)= > > > > 0.0100 > > > > > > > > There are 4 irreducible representations > > > > Representation 1 1 modes -B_2g To be done > > > > > > Representation 2 2 modes -E_2g To be done > > > > > > Representation 3 1 modes -A_2u To be done > > > > > > Representation 4 2 modes -E_1u To be done > > > > G cutoff = 245.0079 ( 259459 G-vectors) FFT grid: ( 32, 32,600) > > > > Largest allocated arrays est. size (Mb) dimensions > > > > Kohn-Sham Wavefunctions 0.34 Mb ( 2220, 10) > > > > NL pseudopotentials 0.07 Mb ( 2220, 2) > > > > Each V/rho on FFT grid 0.59 Mb ( 38912) > > > > Each G-vector array 0.12 Mb ( 16224) > > > > G-vector shells 0.05 Mb ( 6856) > > > > Largest temporary arrays est. size (Mb) dimensions > > > > Auxiliary wavefunctions 1.35 Mb ( 2220, 40) > > > > Each subspace H/S matrix 0.02 Mb ( 40, 40) > > > > Each <psi_i|beta_j> matrix 0.00 Mb ( 2, 10) > > > > The potential is recalculated from file : > > > > ./_ph0/graphene.save/charge-density.dat > > > > > > Starting wfc are 8 atomic + 2 random wfc > > > > > > total cpu time spent up to now is 2.64 secs > > > > > > per-process dynamical memory: 15.0 Mb > > > > > > Band Structure Calculation > > > > Davidson diagonalization with overlap > > > > c_bands: 1 eigenvalues not converged > > > > c_bands: 1 eigenvalues not converged > > > > c_bands: 1 eigenvalues not converged > > > > c_bands: 1 eigenvalues not converged > > > > c_bands: 1 eigenvalues not converged > > > > > > ethr = 1.25E-10, avg # of iterations = 63.7 > > > > > > total cpu time spent up to now is 4392.92 secs > > > > > > End of band structure calculation > > > > Any suggestions on how to speed up the process and if I am missing > > something?! Thank you in advance for all your kind help and time. > > > > Regards, > > > > Faris > > Imperial > > > > > > > > _______________________________________________ > > Pw_forum mailing list > > [email protected] > > http://pwscf.org/mailman/listinfo/pw_forum -- Dr. Lorenzo Paulatto IdR @ IMPMC -- CNRS & Université Paris 6 +33 (0)1 44 275 084 / skype: paulatz http://www.impmc.upmc.fr/~paulatto/ 23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
