[Pw_forum] scf convergence calculation

[Stefano de Gironcoli]

Dear Francesca,

 400 iterations for reaching scf are very many.... there is something 
wrong in your setup...
 Are you sure that your coordinates are correct ?
 By visualizing your input with xcrysden I see that there are gaps in x 
and y directions (in addition to the probably desited one along z) ...
  hope it helps
   stefano


Francesca Costanzo wrote:
> Dear PWSCF users,
>
> I am doing a scf calculation on si(100) slab surface.
> I have tested two pseudo potentials fo silicon to see
> which performs better.
>
> I am wondering why  using
> the   Si.pbe-n-van.UPF and Si.pw91-n-van.UPF pseudoes
> in the first case I can reach quite easily ( after 400 
> iterations) the convergence while in the latter case after 1200 iterations 
> I still don't reach the convergence.
> the mixing beta is 0.5.
>
> Is there something wrong?
>
> Anyway the input file is below:
>
>    # self-consistent calculation
>      cat > si-ex01.in << EOF
> &control
>      calculation='scf'
>      prefix='si',
>      tstress = .true.
>      tprnfor = .true.
>      restart_mode='restart',
>      pseudo_dir ='/sfs/sanfs/home/userincm/incbo407/PWscf/pseudo/',
>      outdir='/scratch/incbo407/au-PWscf/tmp-1/',
>      etot_conv_thr = 1.d-4
>    /
>   &system
>      ibrav = 8, celldm(1) = 29.02243, celldm(2) =1.0, celldm(3)= 0.89771, 
> nat=56, ntyp=2,  ecutwfc=18.0,
>   /
>   &electrons
>      mixing_mode = 'plain'
>      mixing_beta = 0.5
>      conv_thr =  1.0d-8
>   /
>   &ions
>   /
> ATOMIC_SPECIES
> Si 28.086 Si.pw91-n-van.UPF
> H   1     H.pw91-van_ak.UPF
> ATOMIC_POSITIONS {angstrom}
>   Si -.486986953827 -.486915661371 .021837699340
>   Si 3.254734080912 3.254554580350 -.715466406181
>   Si .424995921464 5.989287334956 -.032510900988
>   Si 1.908574447668 7.596205581111 -.896329755432
>   Si 5.990175519344 .425574367605 -.031655667742
>   Si 7.597289525085 1.909448358802 -.895741285772
>   Si 4.863694686691 4.863621862511 -.928089502092
>   Si 9.019734606435 9.020000340300 -.836996926760
>   Si 1.332006439043 4.282396930595 -1.483511378893
>   Si 4.282762677873 1.331640602610 -1.482720710139
>   Si 1.215421638705 9.726643706866 -1.436019240017
>   Si 4.069065518611 6.940868463489 -1.558148325068
>   Si 6.941730748367 4.070143770542 -1.556740812199
>   Si 9.727400143869 1.215885487447 -1.436139812232
>   Si 6.926671693616 9.825186228268 -1.480679150046
>   Si 9.825040961721 6.927019069098 -1.481122837636
>   Si 2.752199364097 -.023268345504 -2.733402882614
>   Si -.022185141426 2.752036538539 -2.734578963613
>   Si 2.755879272416 5.496899501655 -2.970326566691
>   Si -.004779806850 8.317568614429 -2.969974442472
>   Si 8.317316174588 -.004017804657 -2.969192076227
>   Si 5.498360672151 2.755878723458 -2.968474960855
>   Si 8.346177303503 5.558752009571 -2.782863187750
>   Si 5.557877655641 8.346312021303 -2.782400281184
>   Si 1.389966664098 1.388183764950 -4.139518840077
>   Si 1.366337053897 6.940229376004 -4.258916306178
>   Si 4.151574127028 4.149476803004 -4.278767316434
>   Si 4.138929512730 9.694066210006 -4.160002340210
>   Si 6.940071554385 1.366577579401 -4.258586275398
>   Si 9.693861222560 4.139131304691 -4.160296524367
>   Si 6.925553051516 6.926722417990 -4.154730726999
>   Si 9.700291030289 9.701542440060 -4.273212145658
>   Si .000000000000 .000000000000 -5.538591342479
>   Si 2.769296729594 2.769296729594 -5.538591342479
>   Si .000000000000 5.538591342479 -5.538591342479
>   Si 2.769296729594 8.307892305490 -5.538591342479
>   Si 5.538591342479 .000000000000 -5.538591342479
>   Si 8.307892305490 2.769296729594 -5.538591342479
>   Si 5.538591342479 5.538591342479 -5.538591342479
>   Si 8.307892305490 8.307892305490 -5.538591342479
>   H .847478422628 -.846884685755 -6.504440365581
>   H -.847316494390 .847694326946 -6.503794769337
>   H 3.610082118376 1.928241460414 -6.515886469477
>   H 1.917014435899 3.621363118971 -6.495428477030
>   H .852174341536 4.685717428620 -6.494724671289
>   H -.840461532306 6.379649786722 -6.516156349874
>   H 3.616235391428 7.460033933598 -6.504011732009
>   H 1.921872283045 9.155369669764 -6.503953522512
>   H 6.383803828126 -.844617690420 -6.508975414605
>   H 4.685555500382 .852282293694 -6.494454790892
>   H 9.156068183733 1.921926259125 -6.503307926268
>   H 7.460679529841 3.616289367507 -6.504710245978
>   H 6.385587155455 4.690845156163 -6.504170485184
>   H 4.690683227924 6.386073998525 -6.503524888940
>   H 9.160391561857 7.455445966849 -6.494835798512
>   H 7.462679819843 9.153210626588 -6.508329818361
> K_POINTS {automatic}
> 4   4   1  0  0  0
> EOF
>
>
> thank you.
>  		Francesca Costanzo
>