[Pw_forum] Help in cif file atomic positions

[Krishnaiah Kallamadi]

Dear Sir,

Thanks a lot

On Fri, Oct 7, 2016 at 7:05 PM, Michael Mehl <mmehl at usna.edu> wrote:

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>
> Since C and N are neighbors in the periodic table, you could put a
> "virtual" atom at the site, with charge Z = 6.5.  That would at least give
> you the right electron count for the system and preserve the system
> symmetry.  The downside is that a pseudopotential for "Cargen" or
> "Nitrobon" probably doesn't exist, so you'd have to generate it yourself.
> I think VASP is able to handle this somehow, but I've never tried it.
>
> Another alternative is to generate a supercell, randomly populate that
> site with C and N atoms, and average over configurations.  Look up various
> articles by Alex Zunger et al. (http://journals.aps.org/prl/
> abstract/10.1103/PhysRevLett.65.353, to start) on Special Quasirandom
> Structures for some hints on how to do this efficiently.  The downside of
> this is that you'll need a fair number of structures, and you'll lose the
> hexagonal symmetry in the individual calculations.
>
> AFAIK, there aren't any really good solutions for this problem with the
> current generation of DFT codes.  At one time there was some work with the
> Coherent Potential Approximation and KKR (see http://journals.aps.org/
> prb/pdf/10.1103/PhysRevB.67.115109, e.g.), but I don't think any modern
> KKR codes are easily available, much less KKR+CPA.
>
> On Fri, Oct 7, 2016 at 7:50 AM, Krishnaiah Kallamadi <
> krishnsustain at gmail.com> wrote:
>
>> As per my knowledge,
>> espresso can't deal with above cif file. Please help me and correct if I
>> am wrong.
>>
>> On Fri, Oct 7, 2016 at 11:33 AM, Andrius Merkys <andrius.merkys at gmail.com
>> > wrote:
>>
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>>>
>>> Dear Krishna,
>>>
>>> On 07/10/16 08:30, Krishnaiah Kallamadi wrote:
>>>
>>> In a *cif* file attached below, two different atoms have same atomic
>>> positions with occupancy of 0.5. Due to this i am not able to generate *scf.in
>>> <http://scf.in>* file from cif2cell program. Please help me.
>>>
>>>
>>> you have to account for a joint 0.5N+0.5C site at this position. I am
>>> not sure if/how such thing is possible at QE input, but AFAIK, people are
>>> dealing with such models.
>>>
>>> HTH,
>>> Andrius
>>>
>>> --
>>> Andrius Merkys
>>> PhD student at Vilnius University Institute of Biotechnology, SaulÄ—tekio al. 7
>>> LT-10223 Vilnius, Lithuania
>>>
>>>
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>>
>>
>> --
>> Thanks and Regards,
>>
>> K.Krishna
>> JRF, AcSIR-RE
>> CSIR-SERC
>>
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>
>
>
> --
>
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>
> Michael J. Mehl, Ph.D.
>
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-- 
Thanks and Regards,

K.Krishna
JRF, AcSIR-RE
CSIR-SERC
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