[Wien] WARNING : Please restart anew from final position

Fri Jan 21 18:41:18 CET 2011

Dear Laurence,

Thanks a lot. I will follow your advices.

Kakhaber Jandieri

Quoting Laurence Marks <L-marks at northwestern.edu>:

> One general comment: be aware that what you are seeing in both cases
> is (deliberately) a "WARNING", not an "ERROR". You are correct that
> you need to be careful if you see the step size being reduced and make
> sure that you do not have touching or too close to touching spheres.
> In the worst case you will see many of these and the optimization will
> keep trying smaller and smaller steps and not be able to get anywhere.
>
> You also have to be careful if you see the curvature warning, but only
> if this keeps on coming up.  This is one of those subtle things which
> is not described in elementary books on optimization, only in the more
> advanced ones. In 20% (maybe more) of optimizations the curvature
> condition will fail once or twice. This is not a problem, the code is
> smart enough to know what to do. (As the tutorial implies, this often
> happens if the Hessian is changing, e.g. new "bonds" are being
> created.) If it keeps on occurring then (and only then) should you
> start to worry that the forces and energy could be inconsistent.
>
> What you say is reasonable, and probably reducing the RMT of the N a
> little (1.5 ?) would avoid the problem (use clminter, it is designed
> for this). Keep the partially relaxed positions. It is probably safest
> to remove .min_hess and re-run pairhess. (Only do this in case of
> problems, in general a good .min_hess will save a lot of time.)
>
> N.B., RKMAX comes in as RKMAX/min(RMT), so a value of 5 with your
> smallest RMT 1.3 should be more than good enough and I would not go to
> an RKMAX of 7 (too slow, overkill).
>
> On Fri, Jan 21, 2011 at 10:07 AM, Kakhaber Jandieri
> <kakhaber.jandieri at physik.uni-marburg.de> wrote:
>> Dear Laurence,
>>
>> Thank you very much.
>>
>> Unfortunately, after some iteration step  I missed the warnings :
>> WARNING: Step size reduced due to overlapping spheres
>> and
>> WARNING: CURVATURE CONDITION FAILED
>>
>> According to your tutorial, the last one means that the forces and energy
>> are not consistent and one of the possible reasons can be the small RKMAX. I
>> guess that in my case the reason is different since I see the same warning
>> for increased value (7 instead of 5) of RKMAX. May be the reason is given in
>> the first warning about the overlapping spheres. Below I will try to justify
>> my suggestion.
>>
>> I am trying to relax the GaAs slab containing two substitutional nitrogen
>> atoms in surface  layer. I constructed the supercell containing 72
>> non-equivalent atoms: 5 layers with 12 atoms in each, appr. 10 Angstr.
>> Vacuum and the passivation  layer of hydrogen atoms. I fixed only the
>> hydrogen layer and the first GaAs layer. I remember your letter where you
>> had some doubts about such consideration, but I want to compare the
>> simulated Scanning Tunneling Microscopy images with that obtained in Phys.
>> Rev. B75, 035338 (2008), where the similar approach was used (fixed layer,
>> pasivation by hydrogen). So on current stage I decided to stay in frames of
>> this approach.
>>
>> I have the following values of RMT:
>> RMT(Ga)=2, RMT(N)=1.68, RMT(H)=1.3
>>
>> I think that RMT(N)=1.68 is the reason for my problems. The supercell was
>> relaxed correctly up to some iteration step. Then the Ga and N spheres began
>> to touch each other and the problems appeared. I have the following ground
>> for such suggestion. The Ga-N distance in my “partially relaxed” supercell
>> is 1.95 Angstr. and this value is very close to the sum of Ga and N sphere
>> radii.
>>
>> I think that my supercell is not very far from the  full relaxation, since
>> the distances between Ga and N atoms as well as the distance between surface
>> Ga atoms (next neighbors to N atom) and their inward shifts are very close
>> to the values given in Phys.Rev. paper.
>>
>> In spite of that, I still have the great desire to obtain the fully relaxed
>> supercell and accordingly as precise STM image as possible.
>>
>> Could you give me an advice:
>> 1) are my suggestions reasonable?
>> 2) Will the reduction of RMT(N) solve the problem?
>> 3) Is it reasonable to renew the calculations with “partially relaxed”
>> supercell as a starting structure (but of course with reduced value of
>> RTM(N))?
>>
>> Excuse me for so long letter.
>> Beforehand thankful,
>>
>> Kakhaber Jandieri
>>
>>
>>
>> Quoting Laurence Marks <L-marks at northwestern.edu>:
>>
>>> Do grep -e :MIN *.ouptputM -- you need to keep going.
>>>
>>> On Thu, Jan 20, 2011 at 12:30 PM, Kakhaber Jandieri
>>> <Kakhaber.Jandieri at physik.uni-marburg.de> wrote:
>>>>
>>>> Dear Wien2k users,
>>>>
>>>> Using "mini" I see the following message:
>>>>
>>>>>  stop
>>>>>  mini        (00:43:49) 0.880u 0.060s 0:01.25 75.2%  0+0k 0+4024io
>>>>> 0pf+0w
>>>>
>>>>  :WARNING Please restart anew from final position
>>>>
>>>>>  stop forces small, minimization stopped
>>>>
>>>>>  relaxation steps summarized in Surface-GaAs-2N-b.scf_mini
>>>>
>>>>>  relaxed structure and results in Surface-GaAs-2N-b.struct, scf, clmsum
>>>>
>>>>>  please use   save_lapw save_file_name   to save the results
>>>>
>>>>
>>>> Could you explain what is the meaning of
>>>> "WARNING Please restart anew from final position"?
>>>>
>>>> I found a similar question in mailing list (Ghosh SUDDHASATTWA, /Sat Jul
>>>> 24 05:54:54 CEST 2010) but unfortunately without any replied suggestions.
>>>>
>>>> Beforehand thankful,
>>>>
>>>> Kakhaber Jandieri
>>>> /
>>>>
>>>>
>>>> _______________________________________________
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>>>> Wien at zeus.theochem.tuwien.ac.at
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>>>>
>>>
>>>
>>>
>>> --
>>> 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 and imaging 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
>>>
>>>
>>
>>
>>
>> Dr. Kakhaber Jandieri
>> Department of Physics
>> Philipps University Marburg
>> Tel:+49 6421 2824159 (2825704)
>>
>>
>> _______________________________________________
>> 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 and imaging 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
>
>

Dr. Kakhaber Jandieri
Department of Physics
Philipps University Marburg
Tel:+49 6421 2824159 (2825704)