# Re: [Wien] a doubt from threads in case.InM

```So, it does not effect the results if one uses all zeros in respective row
or zero at first three places (x, y, z) and 1.0 at the last place. Correct?```
```

On Fri, Aug 4, 2017 at 12:52 PM, Peter Blaha <pbl...@theochem.tuwien.ac.at>
wrote:

> It is NOT a divisor ! (does not make sense here). Depending on the method
> the 4th value is not used or is eg. a friction term for damped newton
> dynamics.
>
> On 08/04/2017 02:26 AM, Gavin Abo wrote:
>
>> Currently too lazy to check, are the data values x y z div (where div is
>> the divisor)?
>>
>> So (x y z)/div:
>>
>> 0.0. 0.0 0.0 0.0 => (0, 0, 0)/0 = undefined [1] <- If it is not giving a
>> divide by zero error [2], it sounds like the code is able to handle it
>> and may be setting any of these divisions to 0.
>>
>> 0.0. 0.0 0.0 1.0 => (0, 0, 0)/1 = (0, 0, 0) <- This may be safer to use.
>>
>> [1] https://en.wikipedia.org/wiki/Division_by_zero
>>
>> [2]
>> https://software.intel.com/en-us/forums/intel-fortran-compil
>> er-for-linux-and-mac-os-x/topic/392791
>>
>> On 8/3/2017 9:26 AM, fatima DFT wrote:
>>
>>> Thank you very much Sir.
>>> I feel relax now.
>>> I did a heavy calculation using 0.0. 0.0 0.0 0.0 instead of 0.0. 0.0
>>> 0.0 1.0
>>>
>>> So I was worried to repeat the calculation by fixing the position with
>>> 0.0. 0.0 0.0 1.0.
>>>
>>> On Thu, Aug 3, 2017 at 8:31 PM, Laurence Marks
>>> <l-ma...@northwestern.edu <mailto:l-ma...@northwestern.edu>> wrote:
>>>
>>>     Inlined
>>>
>>>     On Thu, Aug 3, 2017 at 9:49 AM, fatima DFT <fatimad...@gmail.com
>>>
>>>         Dear Prof. Peter, Oleg and Marks,
>>>
>>>         I have two queries for case.inM
>>>
>>>         First:
>>>
>>>         I stuck on case.inM file where I want to fix the positions of
>>>         the heavier atom for which I do not want to relax the structure.
>>>
>>>
>>>     A comment: fixing atoms does not do what people think, in general
>>>     it does not make the convergence of QM methods faster (it can for
>>>     CG). The convergence depends upon the number and density of the
>>>     elastic eigenvectors  (PORT) and the elastic-electronic system
>>>     (MSR1a).
>>>
>>>
>>>         In one thread Prof Peter
>>>         <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.
>>> mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_
>>> msg03285.html&d=DwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_
>>> d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=
>>> lMntW40NGNoDrUMHYVU-vXvlVw2pGHikT4XpBt9gMhU&s=-6101yYtzjIzQW
>>> csyC0Zc5AQTUAs08Rf0kz5Ifefu7I&e=>
>>>         mentioned keeping 0 0 0 0 in the respective row of atom that I
>>>         want to constrain. But this four zeros means the entire line
>>>         should be zero
>>>
>>>         0.0 0.0 0.0 0.0   #Atom    1 Generated by pairhess   >>> Say
>>>         it is for La atom.
>>>
>>>         As per Prof Marks
>>>         <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.
>>> mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_
>>> msg12403.html&d=DwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_
>>> d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=
>>> lMntW40NGNoDrUMHYVU-vXvlVw2pGHikT4XpBt9gMhU&s=0fcEvAFHmpT7Za
>>> hxBQYrqD0Xr0DEsgKPFE0Nk-fLeLM&e=>and
>>>         Prof. Oleg
>>>         <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.
>>> mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_
>>> msg01858.html&d=DwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_
>>> d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=
>>> lMntW40NGNoDrUMHYVU-vXvlVw2pGHikT4XpBt9gMhU&s=GJxC2Mi9-
>>> Fts6rULojSPz0X_acMQL2Oe5Ie7WXILcr0&e=>
>>>
>>>         The only first three number should be zero
>>>
>>>         0.0 0.0 0.0 1.0   #Atom    1 Generated by pairhess
>>>
>>>         Could you please clear my doubt that:
>>>
>>>         How the results will differ if I will use "0.0 0.0 0.0 0.0
>>>         #Atom    1 Generated by pairhess" instead of 0.0 0.0 0.0 1.0 ?
>>>
>>>
>>>     I am 99% confident that they are equivalent.
>>>
>>>
>>>         Second:
>>>
>>>         If I use "x pairhess" to generate the case.inM then does it
>>>         copy the case.inM according to the structure files? I just
>>>         tested it for two different structures and I saw two different
>>>         kind of case.inM.
>>>
>>>
>>>     Yes, different structures with different symmetries have different
>>>     symmetry constrained sites so different case.inM.
>>>
>>>
>>>
>>>
>>>         regards
>>>         Fatima
>>>
>>>
>>>
>>>
>>>     --
>>>     Professor Laurence Marks
>>>     "Research is to see what everybody else has seen, and to think
>>>     what nobody else has thought", Albert Szent-Gyorgi
>>>     www.numis.northwestern.edu
>>>     <http://www.numis.northwestern.edu> ; Corrosion in 4D:
>>>     MURI4D.numis.northwestern.edu <http://MURI4D.numis.northwestern.edu>
>>>     Partner of the CFW 100% program for gender
>>>     equity, www.cfw.org/100-percent <http://www.cfw.org/100-percent>
>>>     Co-Editor, Acta Cryst A
>>>
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>>>
>>>
>>>
>>>
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>>
>>
>>
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>>
>>
> --
>
>                                       P.Blaha
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
> Email: bl...@theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
> WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
> --------------------------------------------------------------------------
>
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>
```
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