I guess an easy yet efficient way for generating your alloy structure is to use the Monte Carlo SQS (mcsqs) module which is part of the ATAT gnu software available from:<span></span><div><a href="https://www.brown.edu/Departments/Engineering/Labs/avdw/atat/">https://www.brown.edu/Departments/Engineering/Labs/avdw/atat/</a></div><div><br></div><div>M A H Khalafalla </div><div>Taibah University</div><div>Dept of Physics</div><div><br></div><div>On Friday, October 7, 2016, Krishnaiah Kallamadi <<a href="mailto:krishnsustain@gmail.com">krishnsustain@gmail.com</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Dear Sir,</div><div><br></div>Thanks a lot</div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Oct 7, 2016 at 7:05 PM, Michael Mehl <span dir="ltr"><<a href="javascript:_e(%7B%7D,'cvml','mmehl@usna.edu');" target="_blank">mmehl@usna.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<br><div dir="ltr">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.<div><br></div><div>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. (<a href="http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.65.353" target="_blank">http://journals.aps.org/prl/a<wbr>bstract/10.1103/PhysRevLett.65<wbr>.353</a>, 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.</div><div><br></div><div>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 <a href="http://journals.aps.org/prb/pdf/10.1103/PhysRevB.67.115109" target="_blank">http://journals.aps.org/p<wbr>rb/pdf/10.1103/PhysRevB.67.115<wbr>109</a>, e.g.), but I don't think any modern KKR codes are easily available, much less KKR+CPA.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Oct 7, 2016 at 7:50 AM, Krishnaiah Kallamadi <span dir="ltr"><<a href="javascript:_e(%7B%7D,'cvml','krishnsustain@gmail.com');" target="_blank">krishnsustain@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">As per my knowledge,<div>espresso can't deal with above cif file. Please help me and correct if I am wrong.</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Oct 7, 2016 at 11:33 AM, Andrius Merkys <span dir="ltr"><<a href="javascript:_e(%7B%7D,'cvml','andrius.merkys@gmail.com');" target="_blank">andrius.merkys@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p>Dear Krishna,</p>
<br>
<div>On 07/10/16 08:30, Krishnaiah Kallamadi
wrote:<br>
</div>
</span><span><blockquote type="cite">
<div dir="ltr">In a <b>cif</b> file attached below, two different
atoms have same atomic positions with occupancy of 0.5. Due to
this i am not able to generate <b><a href="http://scf.in" target="_blank">scf.in</a></b> file from cif2cell
program. Please help me. <br>
</div>
</blockquote>
<br></span><span>
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.<br>
<br>
HTH,<br>
Andrius<br>
</span><span><font color="#888888"><pre cols="72">--
Andrius Merkys
PhD student at Vilnius University Institute of Biotechnology, SaulÄ—tekio al. 7
LT-10223 Vilnius, Lithuania</pre>
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