[Wien] lapw1 runs too slow for H2 molecule

Laurence Marks L-marks at northwestern.edu
Fri Oct 10 17:10:42 CEST 2008


Strictly speaking, you should check convergence if you change the RMT.
However if it is only a relatively small change adjusting RMT and
RKMAX in tandem is fine and you won't see much difference.

To be very specific about a caveat, using min(RMT)=2 and RKMAX=7 is
not quite the same as min(RMT)=1 and RKMAX=3.5 -- in my tests often a
slightly larger RKMAX is needed for smaller RMTs.

And as I said before, NEVER compare two calculations with different
RMTs/RKMAX against each other unless you normalize somehow to the same
reference.

On Fri, Oct 10, 2008 at 9:57 AM, Yurko Natanzon
<yurko.natanzon at gmail.com> wrote:
> Dear Laurence,
> thank you for your explanation, it helped me a lot. Yes, I used larger
> RMT for H atom and smaller for H2 molecule.
> Now I see that it is necessary to run convergence tests of total
> energy vs RKmax each time I change RMt radii, is it? for example, when
> I want to optimize positions of lattice constants I have to reduce
> RMTs, so can I also reduce Rkmax proportionally in order to achieve
> better performance?
>
> regards,
> Yurko
>
> 2008/10/10 Laurence Marks <L-marks at northwestern.edu>:
>> The reason is your value for RKMAX.
>>
>> To expand, the largest k-value in lapw1 is determined by
>> RKMAX/min(RMT) which for H2 is 7/0.71. Probably when you did H you had
>> a larger RMT (probably 2.0), so the largest k was 7/2.0 which is about
>> 3 times smaller. Since the size of the matrix you are diagonalizing
>> scales roughly as k**3, for H2 you have a matrix about 27 times larger
>> so it will probably take at least 50 time longer.
>>
>> You can approximately use an RKMAX such that RKMAX/min(RMT) is about
>> the same, i.e. for your H2 molecule use an RKMAX of 2 or 2.5.
>> Unfortunately it is not quite as simple as this and larger RKMAX is
>> better.
>>
>> Note as well that if you want to calculate the atomization energy of
>> H2 you MUST use the same RMT and RKMAX for both H and H2, otherwise
>> your energies are GIGO.
>>
>> N.B., running systems with small RMTs with Wien2k, e.g. for H, is not easy.
>>
>> On Fri, Oct 10, 2008 at 8:23 AM, Yurko Natanzon
>> <yurko.natanzon at gmail.com> wrote:
>>> Dear wien2k users,
>>> I'm running a simple exercise with H2 molecule located in the middle
>>> of a cubic box with a=15 Bohr. the H-H bond length is set to about
>>> 0.75 Ang and RMT radus is 0.71 (also the smaller values were tested).
>>>
>>> The problem is that the calculation is too long. It takes 40 minutes
>>> for LAPW1 to run:
>>> :log
>>>>   (runsp_lapw) options:
>>> Fri Oct 10 11:41:58 CEST 2008> (x) lapw0
>>> Fri Oct 10 11:42:21 CEST 2008> (x) lapw1 -c -up
>>> Fri Oct 10 12:20:05 CEST 2008> (x) lapw1 -c -dn
>>> Fri Oct 10 12:58:24 CEST 2008> (x) lapw2 -c -up
>>> Fri Oct 10 12:58:28 CEST 2008> (x) lapw2 -c -dn
>>> Fri Oct 10 12:58:31 CEST 2008> (x) lcore -up
>>> Fri Oct 10 12:58:31 CEST 2008> (x) lcore -dn
>>> Fri Oct 10 12:58:31 CEST 2008> (x) mixer
>>> For comparison, the same calculation for one H atom in the box  takes
>>> 3 seconds (lapw1), for CoO (a=8 Bohr) - just 12 seconds.
>>>
>>> I used init_lapw -numk 1 -vxc 13
>>> I post my in0 and in1 files as well as a struct file:
>>> --------------in0
>>> TOT   13    (5...CA-LDA, 13...PBE-GGA, 11...WC-GGA)
>>> NR2V      IFFT      (R2V)
>>>  -1 -1 -1    1.00    min IFFT-parameters, enhancement factor  #changed
>>> the default values because of IFFT errors
>>> ---------------in1c
>>> WFFIL        (WFPRI, SUPWF)
>>>  7.00       10    4 (R-MT*K-MAX; MAX L IN WF, V-NMT
>>>  0.30    1  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>>>  0    0.30      0.000 CONT 1
>>>  0.30    1  0      (GLOBAL E-PARAMETER WITH n OTHER CHOICES, global APW/LAPW)
>>>  0    0.30      0.000 CONT 1
>>> K-VECTORS FROM UNIT:4   -9.0       2.0     7   emin/emax/nband
>>> --------------------struct file
>>> h2 molecule
>>> P   LATTICE,NONEQUIV.ATOMS:  2
>>> MODE OF CALC=RELA unit=bohr
>>>  15.117815 15.117815 15.117815 90.000000 90.000000 90.000000
>>> ATOM  -1: X=0.45300000 Y=0.50000000 Z=0.50000000
>>>          MULT= 1          ISPLIT=-2
>>> H 1        NPT=  781  R0=0.00010000 RMT=    0.7100   Z:  1.0
>>> LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
>>>                     0.0000000 1.0000000 0.0000000
>>>                    -1.0000000 0.0000000 0.0000000
>>> ATOM  -2: X=0.54700000 Y=0.50000000 Z=0.50000000
>>>          MULT= 1          ISPLIT=-2
>>> H 1        NPT=  781  R0=0.00010000 RMT=    0.7100   Z:  1.0
>>> LOCAL ROT MATRIX:    0.0000000 0.0000000 1.0000000
>>>                     0.0000000 1.0000000 0.0000000
>>>                    -1.0000000 0.0000000 0.0000000
>>>   8      NUMBER OF SYMMETRY OPERATIONS
>>>  1 0 0 0.00000000
>>>  0-1 0 0.00000000
>>>  0 0-1 0.00000000
>>>       1
>>>  1 0 0 0.00000000
>>>  0-1 0 0.00000000
>>>  0 0 1 0.00000000
>>>       2
>>>  1 0 0 0.00000000
>>>  0 0-1 0.00000000
>>>  0-1 0 0.00000000
>>>       3
>>>  1 0 0 0.00000000
>>>  0 0 1 0.00000000
>>>  0-1 0 0.00000000
>>>       4
>>>  1 0 0 0.00000000
>>>  0 0-1 0.00000000
>>>  0 1 0 0.00000000
>>>       5
>>>  1 0 0 0.00000000
>>>  0 0 1 0.00000000
>>>  0 1 0 0.00000000
>>>       6
>>>  1 0 0 0.00000000
>>>  0 1 0 0.00000000
>>>  0 0-1 0.00000000
>>>       7
>>>  1 0 0 0.00000000
>>>  0 1 0 0.00000000
>>>  0 0 1 0.00000000
>>>       8
>>> --------------------
>>>
>>> With best regards,
>>> Yurko
>>>
>>> --
>>> Yurko (aka Yuriy, Iurii, Jurij etc) Natanzon
>>> PhD Student
>>> Henryk Niewodniczan`ski Institute of Nuclear Physics
>>> Polish Academy of Sciences
>>> ul. Radzikowskiego 152,
>>> 31-342 Krako`w, Poland
>>> Email: Yurii.Natanzon at ifj.edu.pl, yurko.natanzon at gmail.com
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>>
>>
>>
>>
>> --
>> Laurence Marks
>> Department of Materials Science and Engineering
>> MSE Rm 2036 Cook Hall
>> 2220 N Campus Drive
>> Northwestern University
>> Evanston, IL 60208, USA
>> Tel: (847) 491-3996 Fax: (847) 491-7820
>> email: L-marks at northwestern dot edu
>> Web: www.numis.northwestern.edu
>> Chair, Commission on Electron Crystallography of IUCR
>> www.numis.northwestern.edu/
>> Electron crystallography is the branch of science that uses electron
>> scattering to study the structure of matter.
>> _______________________________________________
>> Wien mailing list
>> Wien at zeus.theochem.tuwien.ac.at
>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
>
>
>
> --
> Yurko (aka Yuriy, Iurii, Jurij etc) Natanzon
> PhD Student
> Henryk Niewodniczan`ski Institute of Nuclear Physics
> Polish Academy of Sciences
> ul. Radzikowskiego 152,
> 31-342 Krako`w, Poland
> Email: Yurii.Natanzon at ifj.edu.pl, yurko.natanzon at gmail.com
> _______________________________________________
> Wien mailing list
> Wien at zeus.theochem.tuwien.ac.at
> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>



-- 
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2220 N Campus Drive
Northwestern University
Evanston, IL 60208, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
email: L-marks at northwestern dot edu
Web: www.numis.northwestern.edu
Chair, Commission on Electron Crystallography of IUCR
www.numis.northwestern.edu/
Electron crystallography is the branch of science that uses electron
scattering to study the structure of matter.


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