[Pw_forum] PAW potentials and ecutrho convergence
Joshua Davis
davis101 at chemistry.msu.edu
Tue Sep 23 20:14:22 CEST 2014
Thank you for your help. That would be much appreciated
----------------------------------------------------------------------------------------------------------------
Joshua D. Davis
Graduate Assistant
Department of Chemistry
Michigan State University
578 S. Shaw Lane, room 432
East Lansing, MI 48824
-----------------------------------------------------------------------------------------------------------------
On Tue, Sep 23, 2014 at 1:05 PM, Joshua Davis <davis.d.josh at gmail.com>
wrote:
> Thank you for your help. That would be much appreciated
>
>
> ----------------------------------------------------------------------------------------------------------------
> Joshua D. Davis
>
> Graduate Assistant
> Department of Chemistry
> Michigan State University
>
> 578 S. Shaw Lane, room 432
> East Lansing, MI 48824
>
> -----------------------------------------------------------------------------------------------------------------
>
> On Fri, Sep 19, 2014 at 4:59 PM, Holzwarth, Natalie <natalie at wfu.edu>
> wrote:
>
>> Dear Joshua,
>> If you send me the full input file I will be glad to test the PAW
>> datasets constructed with ATOMPAW code. THe functions on our webpage
>> http://pwpaw.wfu.edu are mostly focused on accuracy in comparison with
>> the all-electron results and may not rapidly converge with ecut. However,
>> there are several other efforts to generate PAW functions that may converge
>> more rapidly.... Sincerely, Natalie Holzwarth
>>
>>
>> N. A. W. Holzwarth email:
>> natalie at wfu.edu
>> Department of Physics web:
>> http://www.wfu.edu/~natalie
>> Wake Forest University phone:
>> 1-336-758-5510
>> Winston-Salem, NC 27109 USA office: Rm. 300 Olin
>> Physical Lab
>>
>> On Fri, Sep 19, 2014 at 4:16 PM, Joshua Davis <davis101 at chemistry.msu.edu
>> > wrote:
>>
>>> The plot of the convergence does look like it is oscillating and sort of
>>> converging to a point but at fairly large energy cut-off. These potentials
>>> were off the "ready to use" potentials on the QE website. Would you have
>>> confidence in the potentials? PAW is the newest method and there are not
>>> many of them. They all use have scalar relativity and not fully
>>> relativity. I figured that would be good enough.
>>>
>>> Thanks
>>>
>>>
>>>
>>> ----------------------------------------------------------------------------------------------------------------
>>> Joshua D. Davis
>>>
>>> Graduate Assistant
>>> Department of Chemistry
>>> Michigan State University
>>>
>>> 578 S. Shaw Lane, room 432
>>> East Lansing, MI 48824
>>>
>>> -----------------------------------------------------------------------------------------------------------------
>>>
>>> On Fri, Sep 19, 2014 at 3:43 PM, Paolo Giannozzi <
>>> paolo.giannozzi at uniud.it> wrote:
>>>
>>>> Maybe the nonlinear core correction is slowly converging,
>>>> especially in Sodium which has s and p semicore electrons
>>>> and a very localized (pseudo-)core charge. Just guessing.
>>>>
>>>> P.
>>>>
>>>> On Fri, 2014-09-19 at 14:20 -0400, Joshua Davis wrote:
>>>> > I was performing a convergence test for the energy cut-off for the
>>>> > density for a set of PAW potentials just to make sure, but I have some
>>>> > results that confuse me a bit.
>>>> >
>>>> >
>>>> > The compound is a NaB5C (space group: Pm-3m) so the potentials I used
>>>> > were:
>>>> >
>>>> > B.pbe-n-kjpaw_psl.0.1.UPF
>>>> > C.pbe-n-kjpaw_psl.0.1.UPF
>>>> > Na.pbe-spn-kjpaw_psl.0.2.UPF
>>>> >
>>>> >
>>>> > The cell was also completely relaxed each time with cell and ion
>>>> > dynamic being "bfgs" algorithm
>>>> >
>>>> >
>>>> >
>>>> > Already did a ecutwfc and kpoint convergence test for each and I found
>>>> > and ecutwfc of 35 Ry and a kpoint mesh of 4x8x8 to be sufficient (I am
>>>> > calculating a cell doubled in one direction).
>>>> >
>>>> >
>>>> > When I did the ecutwfc convergence test I went from 10 to 50 Ry in
>>>> > increments of 5 Ry, and I kept the default ecutrho=4*ecutwfc for each
>>>> > run.
>>>> >
>>>> >
>>>> > so when I did the ecutrho convergence kept ecutwfc at 35 Ry and the
>>>> > kpoints at 4x8x8 and started at 140 and went to 400 Ry.
>>>> >
>>>> >
>>>> > The graph of my convergence is shown below:
>>>> > Inline image 1
>>>> >
>>>> >
>>>> > and if the fourm scrubs the image here is the raw data:
>>>> > ecutrho(Ry),TotalEnergy(ry)
>>>> > 140,-370.0979858
>>>> > 150,-370.0980023
>>>> > 160,-370.0995505
>>>> > 170,-370.1019804
>>>> > 180,-370.1047998
>>>> > 190,-370.1072663
>>>> > 200,-370.1086284
>>>> > 250,-370.1048218
>>>> > 300,-370.1049835
>>>> > 400,-370.1060986
>>>> >
>>>> >
>>>> >
>>>> >
>>>> > The convergence shows a density cut-off of 140 Ry and 150 Ry to be
>>>> > pretty similar in calculated energy, but after that the calculated
>>>> > energy quickly drops until a cut-off of 200 Ry. After that the
>>>> > calculated energy shoots up at a cut-off of 250 Ry by 0.004 then
>>>> > tappers down by 0.002 Ry as it gets to a cut-off of 400 Ry.
>>>> >
>>>> >
>>>> > I thought the energy cut-off for density would be the easiest after
>>>> > ecutwfc and kpoint, but I want to make sure my results would be fine
>>>> > based on what I read for he input documentation for ecutrho. It says
>>>> > ecutrho=4*ecutwfc is usually good (which is pretty standard for the
>>>> > PAW method), but I wanted to make sure. I thought the calculated
>>>> > energy would not have changed or the calculated energy would have
>>>> > converged at a reasonable value.
>>>> >
>>>> >
>>>> > Am I doing something wrong? Is the ratio of ecutwfc and ecutrho too
>>>> > off at the higher energy ecutrho cut-off? Other posts suggest
>>>> > lowering ecutwfc and keeping ecutrho cut-off constant for proper
>>>> > convergence, should I have done this? I figured sneaking up ecutrho
>>>> > would be okay. Am I dumb and this is just an artifact of the PAW
>>>> > method at a large ratio of ecutwfc to ecutrho? Is this an artifact of
>>>> > how the FFT mesh is implemented in QE 5.1? Should I have not gone
>>>> > that high in my density cut-off?
>>>> >
>>>> >
>>>> > Any help would be much appreciated.
>>>> >
>>>> >
>>>> > Other considerations:
>>>> > I used QE 5.1 compiled with ifort 13 and mkl 11.
>>>> >
>>>> >
>>>> > &CONTROL
>>>> > calculation = 'vc-relax',
>>>> > etot_conv_thr = 1.0D-5,
>>>> > forc_conv_thr = 1.0D-4
>>>> > /
>>>> >
>>>> >
>>>> > &SYSTEM
>>>> > ibrav = 0,
>>>> > nat = 14,
>>>> > ntyp = 3,
>>>> > nosym = .TRUE.,
>>>> > nspin = 1,
>>>> > occupations = 'fixed',
>>>> >
>>>> >
>>>> ----------------------------------------------------------------------------------------------------------------
>>>> > Joshua D. Davis
>>>> >
>>>> > Graduate Assistant
>>>> > Department of Chemistry
>>>> > Michigan State University
>>>> > 578 S. Shaw Lane, room 432
>>>> >
>>>> >
>>>> > East Lansing, MI 48824
>>>> >
>>>> >
>>>> -----------------------------------------------------------------------------------------------------------------
>>>> >
>>>> > _______________________________________________
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>>>> > Pw_forum at pwscf.org
>>>> > http://pwscf.org/mailman/listinfo/pw_forum
>>>>
>>>>
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>>>
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>>
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