[Pw_forum] Total energy does not converge with respect to ecut variation

[Seyed Mojtaba Rezaei Sani]

Dear Ari Paavo Seitsonen

Thanks for your useful help. I have done the same calculation with PAW PPs
and it works well. I was trying to compare the results for different PPs.
The total energy converges as following:

100.out:!    total energy              =    -304.89142686 Ry
110.out:!    total energy              =    -306.50366201 Ry
120.out:!    total energy              =    -307.43570677 Ry
130.out:!    total energy              =    -307.95403074 Ry
140.out:!    total energy              =    -308.24111628 Ry
150.out:!    total energy              =    -308.40041680 Ry
160.out:!    total energy              =    -308.48642232 Ry
170.out:!    total energy              =    -308.53269562 Ry
175.out:!    total energy              =    -308.54709116 Ry

I am worry about choosing such a high ecutwfc for the system. Does it make
any trouble in calculations except prolonging them?


On Sun, Jan 25, 2015 at 12:35 PM, Ari P Seitsonen <Ari.P.Seitsonen at iki.fi>
wrote:

>
> Dear Seyed Mojtaba Rezaei Sani,
>
>   I would assume the Cu-HTH-pseudo potential to require a cut-off energy
> higher than 100 Ry, they are quite hard ones. If you are able to use the
> PAW method, you can find the data sets for example in the PSlibrary of
> Andrea Dal Corso, http://qe-forge.org/gf/project/pslibrary/ .
>
>     Greetings from Trieste,
>
>        apsi
>
> -=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=-=*=
> -=*=-=*=-=*=-=*=-
>   Ari Paavo Seitsonen / Ari.P.Seitsonen at iki.fi / http://www.iki.fi/~apsi/
>   Ecole Normale Supérieure (ENS), Département de Chimie, Paris
>   Mobile (F) : +33 789 37 24 25    (CH) : +41 79 71 90 935
>
>
>
> On Sun, 25 Jan 2015, Seyed Mojtaba Rezaei Sani wrote:
>
>  Dear all
>> I was performing an optimizing calculation for the kinetic energy cutoff
>> of  wavefunctions expansion for Cu3N compound with a cubic structure using
>> QE v.5.1.
>> Results don't show any convergence neither in total energies nor in
>> differences.
>> Here is the table for the calculation result
>>
>> 25.out:!    total energy              =    -224.54499924 Ry
>> 30.out:!    total energy              =    -231.56190061 Ry
>> 35.out:!    total energy              =    -239.33860506 Ry
>> 40.out:!    total energy              =    -247.75926085 Ry
>> 45.out:!    total energy              =    -256.35103303 Ry
>> 50.out:!    total energy              =    -264.81580643 Ry
>> 55.out:!    total energy              =    -272.59279950 Ry
>> 60.out:!    total energy              =    -279.38896704 Ry
>>
>> I chose these PPs:
>>
>> Cu.pbe-d-hgh.UPF
>> N.pbe-hgh.UPF
>>
>> and this an input file:
>>
>> &CONTROL
>>   calculation = 'scf'
>>   verbosity = 'high'
>>   restart_mode = 'from_scratch'
>>   wf_collect = .TRUE.
>>   nstep =  100
>>   tstress = .TRUE.
>>   tprnfor = .TRUE.
>>   outdir = './tmp'
>>   prefix = 'Cu3N'
>>   etot_conv_thr = 0.0001
>>   forc_conv_thr = 0.0001
>>   pseudo_dir = '/home/rezaei/work/cu_pnictide/pseudo'
>> /
>> &SYSTEM
>>   ibrav = 1
>>   celldm(1) = 7.217
>>   nat = 4
>>   ntyp = 2
>>   ecutwfc = 25
>>   ecutrho = 100.0
>>   occupations = 'smearing'
>>   degauss = 0.02D0
>>   smearing = 'mv'
>> /
>> &ELECTRONS
>>   electron_maxstep = 100
>>   conv_thr = 1.0d-6
>>   mixing_mode = 'TF'
>>   mixing_beta = 0.7D0
>>   diagonalization = 'cg'
>> /
>> ATOMIC_SPECIES
>>   Cu   63.5460  Cu.pbe-d-hgh.UPF
>>   N    14.0067  N.pbe-hgh.UPF
>> ATOMIC_POSITIONS {alat}
>>   N        0.000000000   0.000000000   0.000000000
>>   Cu       0.000000000   0.500000000   0.000000000
>>   Cu       0.500000000   0.000000000   0.000000000
>>   Cu       0.000000000   0.000000000   0.500000000
>> K_POINTS {automatic}
>>   10 10 10  1 1 1
>>
>> I appreciate any help in advance.
>>
>>  Best regards,
>>
>> --
>> Seyed Mojtaba Rezaei Sani
>>
>> Institute for Research in Fundamental Sciences (IPM)
>> School of Nano-Science
>> Shahid Farbin Alley
>> Shahid Lavasani st
>> P.O. Box 19395-5531
>> Tehran, Iran
>> Tel: +98 21 2310  (3069)
>>
>>
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-- 
Seyed Mojtaba Rezaei Sani

Institute for Research in Fundamental Sciences (IPM)
School of Nano-Science
Shahid Farbin Alley
Shahid Lavasani st
P.O. Box 19395-5531
Tehran, Iran
Tel: +98 21 2310  (3069)
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