[Pw_forum] Error: fft order too large

[WF]

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

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     from  good_fft_order  : error #      2241

      fft order too large

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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 32.070000 S.vdwDF-tmus-tmc.UPF

Mo 95.940000 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

 

 

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F, Wu

College of Chemistry and Molecular Engineering Peking University

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