[Pw_forum] Error: fft order too large
Hello everyone, I am calculating a surface slab model of MoS2. My parameter works well with 5~11 layers. But with 13 layers ( 39 atoms total ), it gives %% from good_fft_order : error # 2241 fft order too large %% Decreasing Ecutwfc/Ecutrho can eliminate these problem. But these Ecutwfc/Ecutrho is determined by convergence test of bulk lattice parameter test, so I would like to find a way to solve this problem without decreasing Ecutwfc/Ecutrho. Is there any suggestion ? My input file is like this: ( all 5~11layers input files are just same except atoms related part ) == &control calculation = 'relax' restart_mode = 'from_scratch' tstress = .true. tprnfor = .true. outdir = './out' wfcdir = './wfc' prefix = 'MoS2' / &system ntyp = 2 nat = 39 ibrav = 4 celldm(1) = 6.108157 celldm(3) = 40.745230 ecutwfc = 100.0 ecutrho = 800.0 london = .false. / &electrons diagonalization = 'cg' mixing_mode = 'plain' mixing_beta = 0.7 conv_thr = 1.00d-08 / &ions ion_dynamics = 'bfgs' ion_positions = 'default' / ATOMIC_SPECIES S 32.07 S.vdwDF-tmus-tmc.UPF Mo 95.94 Mo.vdwDF-rrkjus-tmc.UPF (Atomic position is negelected for it is too long) K_POINTS automatic 8 8 1 1 1 1 = Best Regards, F, Wu --- F, Wu College of Chemistry and Molecular Engineering Peking University -- -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110915/862b0759/attachment.htm
[Pw_forum] Error: fft order too large
On Sep 15, 2011, at 4:31 , WF wrote: > from good_fft_order : error # 2241 fft order too > large > > Is there any suggestion ? > look into the code. You will find that there is a maximum fft dimension (nfftx, currently set to 2048). There is nothing special about this number: it is just a check. If you really need a FFT dimension larger than 2048, just increase nfftx and recompile P. --- Paolo Giannozzi, Dept of Chemistry&Physics&Environment, Univ. Udine, via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222
