[Pw_forum] convergence w.r.t ecutwfc

[Amin Torabi]

Dear Mohnish,

Based on the following experimental papers, diborane has 16 atoms in a
monoclinic unit cell (c=4.4A, b=5.72A, a=6.5A and g=105.1deg), and as far as
I can understand, this is what XcrysDen is showing

Smith, H. W.; Lipscomb, W. N. J. Chem. Phys. 1965, 43, 1060–1064.
Jones, D. S.; Lipscomb, W. N. J. Chem. Phys. 1969, 51, 3133–3134

And please notice that the atomic positions are in "crystal".

Now, could you please further explain your comment, because I am afraid I
didn't get your point.

Many thanks
Amin



On Mon, Aug 29, 2011 at 3:25 AM, mohnish pandey <mohnish.iitk at gmail.com>wrote:

> 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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>


-- 
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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