[Pw_forum] convergence w.r.t ecutwfc

[mohnish pandey]

Dear Amin!

Are you trying to calculate the energy of BH3 dimer? If it so then the
vacuum space you have used is very less, there will be lot of spurious
interaction. Increase the vacuum space such that the minimum distance
between the images is greater than 15 angstrom. Please try it.

On Mon, Aug 29, 2011 at 4:04 AM, Amin Torabi <mtorabi at uwo.ca> wrote:

> Dear QE-users,
>
>
> Will you please take a look at my input file and convergence table below:
>
> I am using PBE USPP for both hydrogen and boron, but calculating energies
> using PBEsol. (ecutrho is set to 12* ecutwfc.)
>
> My question is:
> 1. Does it look normal? I was expecting to see 1mRy accuracy at lower
> ecutwfc values.
> 2. I didn't use "occupations" or "smearing" and I didn't get any error in
> output files. Do they affect the convergence?
> 3. I want to do vc-relax calculation at high pressure. Based on my table,
> what ecutwfc do you suggest?
>
> Thanks in advance.
>
>
>
> ecutwfc                  energy
> 30                       -38.28149597
> 35                       -38.28437812
> 40                       -38.28554856
> 45                       -38.28658930
> 50                       -38.28772083
> 55                       -38.28883141
> 60                       -38.28989311
> 65                       -38.29086868
> 70                       -38.29167889
> 75                       -38.29227767
> 80                       -38.29267847
> 85                       -38.29291696
> 90                       -38.29302834
> 95                       -38.29305836
> 100                      -38.29305908
> 105                      -38.29307545
> 110                      -38.29313486
> 115                      -38.29324982
>
>  &control
>         pseudo_dir = **
>         outdir          = **
>         prefix          = '$a'
>         tstress         = .true
>         tprnfor         = .true
>         verbosity     = 'low'
>  /
> &SYSTEM
>         ibrav             = 12
>         celldm(1)       = 8.31479435
>         celldm(2)       = 1.3
>         celldm(3)       = 1.4772727273
>         celldm(4)       = -0.260504508642648
>         nat                = 16
>         ntyp              = 2
>         ecutwfc         = $a
>         ecutrho          = `expr 12 \* $a`
>         input_dft        = 'pbesol'
>  /
> &ELECTRONS
>  /
> ATOMIC_SPECIES
>  B  10.811    B.pbe-n-van_ak.UPF
>  H  1.00794   H.pbe-van_ak.UPF
> ATOMIC_POSITIONS crystal
> B        0.002   0.146   0.042
> H       -0.194   0.166   0.140
> H        0.196   0.294  -0.005
> H        0.104  -0.019   0.112
> B       -0.002  -0.146  -0.042
> H        0.194  -0.166  -0.140
> H       -0.196  -0.294   0.005
> H       -0.104   0.019  -0.112
> B        0.498   0.354   0.542
> H        0.694   0.334   0.640
> H        0.304   0.206   0.495
> H        0.396   0.519   0.612
> B        0.502   0.646   0.458
> H        0.306   0.666   0.360
> H        0.696   0.794   0.505
> H        0.604   0.481   0.388
> K_POINTS automatic
>  8 8 8  0 0 0
>
> --
> Amin Torabi
> Ph.D. Student
> Chemistry Department
> The University *of* Western Ontario
> London, On Canada, N6A 5B7
> Phone: 519-661-2111 Ext: 87871
> ****************************************
>
>
>
> --
> Amin Torabi
> Ph.D. Student
> Chemistry Department
> The University *of* Western Ontario
> London, On Canada, N6A 5B7
> Phone: 519-661-2111 Ext: 87871
> ****************************************
>
>
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>


-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
BTech-Mtech, IIT Kanpur
Senior Project Associate,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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