[Pw_forum] Convergence of relax of slab calculation

[Ari P Seitsonen]

Dear Ben Liew,

   Without looking at the structure itself, adding to the previous comment 
about the algorithm for mixing, you have not really given any initial 
magnetic moments even if you have 'nspin = 2': The 
'starting_magnetization(1) = 0.0' does not give any preferential spin 
ordering. Do you know something about this, is the system expected to be 
ferromagnetic, antiferromagnetic, ...?

   Tiny issues, I usually do the first calculation without the surface 
dipole as it makes the convergence always a bit trickier; and your
'B ~= 2 * A', but you give the same number of k points in both directions. 
(I usually tend to use smearing schemes where the occupations are 
guaranteed to be in the physical range of [0:1], but this is just a 
personal preference and should thus be ignored)

     Greetings,

        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 Wed, 5 Aug 2015, ben liew wrote:

> Dear PWSCF users,
> 
> Hi, I am a new user of Pwscf. I am working on slab calculation for pyrolusite MnO2 (110) surface with 3 atomic layers calculation and fixed bottom 2 layers and only top atomic
> layer is allowed to be relaxed. I have also include the dipole correction for the calculation to counteract with the interaction between slabs. However, my calculation doesn't
> seems to be converged as the scf accuracy is not decreasing over each iteration. Below is the estimated scf accuracy after hundreds of iterations, it is not converging 
> 
>      estimated scf accuracy    <     373.64728976 Ry
>      estimated scf accuracy    <     106.52177156 Ry
>      estimated scf accuracy    <      96.97567125 Ry
>      estimated scf accuracy    <     207.03807187 Ry
>      estimated scf accuracy    <     132.53045831 Ry
>      estimated scf accuracy    <      77.19101827 Ry
>      estimated scf accuracy    <     112.41885075 Ry
>      estimated scf accuracy    <      93.27430429 Ry
>      estimated scf accuracy    <     116.68049786 Ry
>      estimated scf accuracy    <     587.09711027 Ry
>      estimated scf accuracy    <     374.45312501 Ry
>      estimated scf accuracy    <     106.89811469 Ry
>      estimated scf accuracy    <      96.84898888 Ry
>      estimated scf accuracy    <     207.83006869 Ry
>      estimated scf accuracy    <     132.74588293 Ry
>      estimated scf accuracy    <      77.09445200 Ry
>      estimated scf accuracy    <     112.41688597 Ry
>      estimated scf accuracy    <      93.57796273 Ry
>      estimated scf accuracy    <     116.25663912 Ry
>      estimated scf accuracy    <     587.39968959 Ry
>      estimated scf accuracy    <     374.91438307 Ry
>      estimated scf accuracy    <     106.71641516 Ry
>      estimated scf accuracy    <      96.75392736 Ry
> 
> I have include my input file as followed. Can anyone tell me is that any problem with my input file? 
> 
>  &control
>     calculation = 'relax'
>     tstress=.true.
>     tprnfor=.true.
>     pseudo_dir='/home/ben/Downloads/espresso-5.1.2/pseudo'
>     outdir='./vc3'
>     prefix='pyrolusite'
>     tefield=.true.
>     dipfield=.true.
>  /
>  &system
>     ibrav=8,
>     A=2.8563, B=6.2199, C=20.0
>     nat=18, ntyp=2,
>     starting_magnetization(1)=0.0
>     nspin=2
>     ecutwfc=37.0
>     ecutrho=250.0
>     occupations='smearing'
>     smearing='m-v'
>     degauss=0.01
>     edir=3
>     emaxpos=0.5
>     eopreg=0.1
>     eamp=0.001
>  /
>  &electrons
>     electron_maxstep=500
>     conv_thr=1.0d-6
>     mixing_beta=0.7
>  /
>  &ions
>     ion_dynamics='bfgs'
> /
> ATOMIC_SPECIES
>   Mn 54.9380  Mn.pbe-spn-kjpaw_psl.0.3.1.UPF
>   O  15.9994  O.pbe-kjpaw.UPF
> ATOMIC_POSITIONS (angstrom)
> O         1.428129   3.109734   0.000000  0  0  0
> O         1.428129   0.000241   0.652526  0  0  0
> Mn       1.428129   3.109896   1.883398  0  0  0
> O         0.000000   1.885646   1.883398  0  0  0
> O         0.000000   4.334118   1.883398  0  0  0
> Mn       0.000000   0.000062   1.883398  0  0  0
> O         0.000000   5.014614   4.987475  0  0  0
> O         0.000000   1.205401   4.987475  0  0  0
> Mn       0.000000   3.109816   4.987475  0  0  0
> Mn       1.428129   0.000027   4.987475  0  0  0
> O         1.428129   3.109734   3.767387  0  0  0
> O         1.428129   0.000241   3.114269  0  0  0
> O         1.428129   3.109734   6.207560
> O         1.428129   0.000241   6.860698
> Mn       1.428129   3.109896   8.091569
> O         0.000000   1.885646   8.091569
> O         0.000000   4.334118   8.091569
> Mn       0.000000   0.000062   8.091569
> K_POINTS (automatic)
>   5 5 1 0 0 0
> 
> Your comments and suggestion is much appreciated.Thank you.
> 
> 
> Best Regards,
> Ben Liew
> Ph.D Student
> Fuel Cell Institute,
> The National University of Malaysia,
> 43600 Bangi,
> Selangor, Malaysia.
> Contact no. : +6016 552 0878
> Email           : liewkienben at gmail.com
> 
>