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

[Paolo Giannozzi]

Correct, but scf convergence in CP is not THAT slow. The default value of
the time step is dt=1, if I remember correctly. A value around 10 should
yield a much faster convergence.

Paolo



On Fri, Mar 12, 2021 at 10:18 AM Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:

>
> Dear Chris
> scf convergence with cp.x actually used to be painfully slow! For this
> reason, pw.x and cp.x should be interoperable, that is, you should be
> able to restart a converged pw.x calculation with cp.x. Have a look
> into the CPV/Restart_example/ directory, where restart details are
> explained.
> HTH
> Giuseppe
>
> Quoting Christoph Wolf <wolf.christoph at qns.science>:
>
> > 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
>
>
>
> GIUSEPPE MATTIOLI
> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
> Via Salaria Km 29,300 - C.P. 10
> I-00015 - Monterotondo Scalo (RM)
> Mob (*preferred*) +39 373 7305625
> Tel + 39 06 90672342 - Fax +39 06 90672316
> E-mail: <giuseppe.mattioli at ism.cnr.it>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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