[Pw_forum] Question on phonon calculation of MgB2.

[Paolo Giannozzi]

On Thursday 28 July 2005 10:57, 张 洪彬 wrote:

> so it seems like that E1u, A2u, and B1g have reached the convergence,
> while E2g varies as degauss value, since electron-phonon coupling for
> this modes is very strong, so is this the reason why it varies?

this is the reason, and it is well known to everybody who has tried
to do calculations on MgB2. It is very hard to achieve converged
values for the frequency of the E2g mode, and even harder for 
electron-phonon coefficients.

> Further more, for ecutwfc=50, I didn't get the converged value for A2u
> mode(692), but I think ecutwfc=50 is so large a value, is there anything
> else to improve? PP? 

convergence with the cutoff depends mostly on pseudopotentials

Paolo

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Paolo Giannozzi             e-mail:  giannozz at nest.sns.it
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