[Pw_forum] regarding convergence of system

[Pascal Boulet]

Hello,

At first glance:

1.The mixing parameter is probably to high: try 0.2 instead of 0.7.
2.Do you need electron smearing? Is it a metal? If not, I would first try occupation=‘fixed’ together with nbnd=n (number of orbitals valence+conduction) and remove smearing and degauss keywords.
3. This an oxide, you might need DFT+U… I do not know for sure.

At 2nd glance: please give your affiliation!

HTH,
Pascal

-
Pascal Boulet - MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE
Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie Niemen - 13013 Marseille
Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50
Site : http://allos.up.univ-mrs.fr/pascal - Email : pascal.boulet at univ-amu.fr


Le 4 oct. 2016 à 12:15, Amita Sihag <sihag.amita at gmail.com> a écrit :

> Dear all
> I am trying to converge a supercell(2*2*1) of LaCoO3. The system is not converged even after 500 iterations and 6 days. It is not achieving convergence after so long.Please suggest the necessary. It will be a great help.I am posting the input file of system
> 
> &CONTROL
>                        title = 'LaCoO3' ,
>                       prefix = 'LaCoO3'
>                  calculation = 'vc-relax' ,
>                  max_seconds = 1.0d+7 ,
>                 restart_mode = 'from_scratch'
>                       outdir = '/home/SSM_grp/amitasihag/LaCoO3/221/nonmagnetic/out' ,
>                   pseudo_dir = './' ,
> /
> &SYSTEM
>                        ibrav = 0,
>                     celldm(1)= 1.89 ,
>                          nat = 40,
>                         ntyp = 3,
>                      ecutwfc = 30 ,
>                      ecutrho = 300 ,
>                  occupations = 'smearing' ,
>                     smearing = 'gaussian' ,
>                      degauss = 0.020
> /
> &ELECTRONS
>             electron_maxstep = 1500 ,
>                     conv_thr = 1.0d-4 ,
>                  mixing_mode = 'plain' ,
>                  mixing_beta = 0.7 ,
>              diagonalization = 'david' ,
> 
> /
> &IONS
> /
> &CELL
> /
> CELL_PARAMETERS alat
>   11.145365372  -0.712543576  -0.511263360
>    4.817125474  10.076876074  -0.512591875
>    2.406770662   1.411311463   4.846536018
> 
> ATOMIC_SPECIES
>    La   138.91 La.pbe-nsp-van.UPF
>    Co   58.933 Co.pbe-sp-van.UPF
>    O    15.999 O.pbe-van_ak.UPF
> ATOMIC_POSITIONS alat
> La       2.570235772   1.475769989   1.203980885
> La       5.043826568   6.594009649   0.701404953
> La       8.208023646   1.169121254   0.739924489
> La      10.540444808   6.193518050   0.672086391
> La       7.828816665   4.582125889   3.150594320
> La      10.161237827   9.606522686   3.082756222
> La      13.325435071   4.181634280   3.121275751
> La      15.799025866   9.299873941   2.618699819
> Co       0.000000000   0.000000000   0.000000000
> Co       2.408562737   5.038438038  -0.256295937
> Co       5.572682687  -0.356271788  -0.255631680
> Co       7.981245423   4.682166250  -0.511927617
> Co       5.193223752   3.052636419   2.165050529
> Co       7.602625127   8.080210085   1.913608150
> Co      10.766636570   2.695433772   1.909072328
> Co      13.176037945   7.723007437   1.657629949
> O        6.992683749   5.929956840   3.249477607
> O        9.402656127  10.967922022   2.996121010
> O       12.568245646   5.570689038   2.997441518
> O       14.982978449  10.597343273   2.736823953
> O        3.386282547   0.178300388   1.085856789
> O        5.801015207   5.204954323   0.825239239
> O        8.966605535  -0.192278403   0.826559701
> O       11.376577768   4.845686479   0.573203119
> O        7.789346679   3.623570534   4.584043374
> O       10.199663612   8.717912060   4.247900859
> O       13.363561035   3.352073083   4.210598832
> O       15.771782625   8.288580019   4.090623371
> O        2.597478896   2.487063627  -0.267942599
> O        5.005700775   7.423571164  -0.387918090
> O        8.169597743   2.057731597  -0.425220079
> O       10.579914964   7.152073724  -0.761362624
> O        8.554085222   4.145085667   2.016871101
> O       11.033664829   9.142012963   1.654431985
> O       14.196470737   3.749360741   1.656499814
> O       16.536162443   8.824852211   1.505548708
> O        1.833099424   1.950791650   2.317132061
> O        4.172791165   7.026283196   2.166180951
> O        7.335596976   1.633630902   2.168248787
> O        9.815176618   6.630558274   1.805809668
> K_POINTS automatic
> 2 2 4  0 0 0
>                  
> Thank you 
> Amita 
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