[Pw_forum] Question on el-ph calculations

[MKondrin]

Сергей Ерохин wrote:
> Dear Dr. Kondrin,
>
> Thank you for your answer, however I found in the forum that
> ||||||||||||||||||||||||||||
> If your k point grid is fine enough, if you plot lambda as a function of 
> the broadening there is a plateau, i.e. it looks like this:
>
> lambda
> ^
> |/\
> /|/ \
> /|/   \______    <-- converged value
> /|/                  \
> /|/_________\__> broadening
> /
>
> The correct value of lambda is the one on the plateau
> http://qe-forge.org/pipermail/pw_forum/2014-October/105303.html
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>
> And I wonder what value of broadening should be taken to get this 
> plateau. Understand that this value must be small but how far. Could I 
> expect that in my case the plateau at broadening ~0.2.
>
>
> -- 
> Sergey Erohin
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>
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Dear Sergey!

First, in your case it is not quite clear what is plateau. Second, in 
the thread you cited degauss values are well below 0.1. If you are 
interested in superconducting properties you should consider quite low 
temperatures (around Tc), so there is no reason why electron 
distribution function should be very broaded. Larger degauss values mean 
larger temperature which in its turn destroy superconductive state. So 
your graph (if one does not take into account too large degauss values) 
just illustrate this.

Best regards,
M.V.Kondrin