[QE-users] SCF convergence of cp.x vs. pw.x

[Christoph Wolf]

Dear all,

I am trying to run an SCF calculation in cp.x (because I want to use the
spin contamination analysis of cp.x), however reaching convergence with
cp.x seems painfully slow - probably my fault as I am not familiar with
cp.x.

System is a spin polarized calculation for a molecule in a vacuum box. The
SCF calculation converges in 30 steps:

!    total energy              =    -813.86536682 Ry
     Harris-Foulkes estimate   =    -813.86536682 Ry
     estimated scf accuracy    <          1.3E-11 Ry

But the cp.x calculation is still running after 2000 steps

1997    0.000605472420187    0.0    0.00    -406.607110121158
 1998    0.000604666115183    0.0    0.00    -406.607351342414
1999    0.000603861731893    0.0    0.00    -406.607592243454
...

(NB: the energy difference between CP and PW at this point is ~0.650182333
Ry)

I am running the cp.x calculation with

calculation = 'scf'
and electron_dynamics = 'damp

Is that the right way to do this? If yes, am I missing some critical
parameters for improving convergence?

I attached my input below - any help is much appreciated!

Best,
Chris

&CONTROL
  calculation = "scf"
  prefix = "fepc"
  pseudo_dir = "/home/chwolf/Work/DFT/00_pseudo/"
  outdir = "tmp"
  wf_collect = .true
  tprnfor = .true.
  restart_mode = "from_scratch"
  nstep      = 2000
/
&SYSTEM
   ibrav = 0
   nat  = 57
   ntyp = 4
   nspin = 2
   occupations = "fixed"
   ecutwfc = 60
   ecutrho = 240
   tot_magnetization=1
   tot_charge=-1
   starting_magnetization(1) = 0.5
   starting_magnetization(2) = 0.0
   starting_magnetization(3) = 0.0
   starting_magnetization(4) = 0.0
   nr1b=24, nr2b=24, nr3b=12
/
&ELECTRONS
  conv_thr=1e-10
  electron_maxstep = 350
  electron_dynamics = 'damp'
/

CELL_PARAMETERS angstrom
29.47070000000000 0.00000000000000 0.00000000000000
0.00000000000000 29.47070000000000 0.00000000000000
0.00000000000000 0.00000000000000 15.000

ATOMIC_SPECIES
Fe    55.9330    Fe_ONCV_PBE_sr.upf
C     12.0107    C_ONCV_PBE_sr.upf
N     14.0067    N_ONCV_PBE-1.0.upf
H      1.0000    H_ONCV_PBE_sr.upf

ATOMIC_POSITIONS angstrom
...
..

--
IBS Center for Quantum Nanoscience
Seoul, South Korea
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