[Pw_forum] electron-phonon calculation problem

[yelena]

Dear Paul and Paolo,

Thank you very much for your reply. I guess manually fixing will have 
to do the trick.

And I am specially grateful for link to w2gz site. I started reading 
texts, there are some really interesting things there.
I will feel free to send you an email if I have some questions. I hope 
this is ok.

Best regards,
Jelena

P.S. If mid-70s were "the bad old days" you should see it now :( No 
matter what people say, seventies were the golden age after all. Yet, 
countryside is still beautiful :)


On 2016-04-15 05:03, W2AGZ wrote:
> Dear J. Pesic,
>
> I understand your frustration, and Paolo's response is very 
> cogent...the
> Fortran "ones and zeroes" at k(q) near zero need to be tuned "a 
> priori or a
> posteriori"  in either lambda.f90 and/or its output.  I've dealt with 
> this
> issue over the years attempting to calculate the Eliashberg-McMillan 
> strong
> coupling superconductivity parameters in copper oxide perovskites.  
> Please
> visit www.w2agz.com for relevant publications/presentations and 
> references.
> I've found some success combining algorithms and code from PWSCF, 
> GIBBS2,
> and ELK.
>
> I visited and spoke at your institute in Belgade back in "the bad old 
> days"
> of the mid-1970s, and recall fondly the hospitality of the faculty 
> and the
> beauty of the contryside.
>
> Best, -Paul
>
> -----Original Message-----
> From: pw_forum-bounces at pwscf.org [mailto:pw_forum-bounces at pwscf.org] 
> On
> Behalf Of yelena
> Sent: Thursday, April 14, 2016 6:49 AM
> To: pw_forum at pwscf.org
> Subject: [Pw_forum] electron-phonon calculation problem
>
> Dear all,
> I've been having problem with electron-phonon calculation. I keep 
> having
> negative phonon frequency in gamma point, -0.00007, nowhere else, (so 
> it is
> not "real" instability, but some numerical problem) but it keeps 
> interfering
> with my lambda.x calculation and all i get is NAN for alpha2F and so 
> on. So
> is there any trick to avoid it? This is clearly numerical issue, 
> because
> other modes are positive and phonon dispersion looks as it should be 
> and
> there is no any instability. Can I somewhere manually change that -, 
> maybe?
> I've tried to increase tr2_ph (and decrease it, also) but it keeps 
> happening
> just the same. And tried larger k and q grid. Still the same.
>
> Best Regards,
> PhD Student J.Pesic
> Center for Solid State Physics,
> Institute of Physics Belgrade, Serbia
>
>
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