[QE-users] [SPAM] Re: Different SCF energy when # of MPI is changed

[Paolo Giannozzi]

On 06/10/2022 09:18, Takahiro Chiba wrote:
> It does not always happen. For example, no discrepancy was found with
> the "ausurf" benchmark. Therefore, I expect there is something wrong
> with my input rather than compile/install issues.

it's not necessarily something wrong in your input. Apparently your run 
is quite hard to converge. Even the numerical noise that is unavoidable 
in a large calculation may occasionally lead the scf procedure towards a 
different path that converges badly (or better), for no apparent good 
reason. Notice that the run that exhibits the largest discrepancy in the 
energy (the one with 32 processors) is also the one that makes a 
disproportionate number of iterations (452 vs 63-67 for the three other 
runs).

Something that might help is to use a larger broadening (degauss) and a 
gaussian broadening

Paolo

> 
> 
> 
> ---Sender---
> Takahiro Chiba
> Grad. school of chem. sci. and eng., Hokkaido Univ.
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Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
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