[Pw_forum] PAW potentials and ecutrho convergence
Holzwarth, Natalie
natalie at wfu.edu
Fri Sep 19 22:59:11 CEST 2014
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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