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

[Paolo Giannozzi]

By the way: if I remember correctly, CP and PW do not give the same energy
for charged cells. The difference is given by the net charge times the
quantity 'Delta V(G=0)' printed in the output of CP

Paolo

On Fri, Mar 12, 2021 at 10:23 AM Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> 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
>
>

-- 
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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