[QE-users] Clarification on the diffusion coefficient calculation

[Kazume NISHIDATE]

Dear Mauro Francesco Sgroi,

> the diffusion coefficient is calculated using the full trajectory
>  from the initial step or just using the last part of the trajectory
>  calculated with the restarted calculation?

This would mean that the diffusion constant evaluated from the "full
trajectory" was different from the evaluated one only using the "later
part of the trajectoroy". Right?

In this case, the calculated diffusion cofficient is apparently
affected by its 'particular' initial configuration and hence it is not
suitable as a diffusion "constant" because it will vary depending on
the initial configulation.

The effect of the initial configuration may be weired off after
several hundred thousand MD time steps, and you should always use the
later part of the trajectory data to evaluate the diffusion
"constant".


> 2023/03/24 19:49、Mauro Francesco Sgroi <maurofrancesco.sgroi at unito.it>のメール:
> 
> Dear all,
> I would need a clarification about the calculation of the diffusion coefficient.
> Using the restart function, the diffusion coefficient is calculated using the full trajectory from the initial step or just using the last part of the trajectory calculated with the restarted calculation?
> 
> Many thanks in advance and best regards,
> Mauro Sgroi.
>  _______________________
> Dr. Mauro Francesco Sgroi
> Department of Chemistry University of Turin
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西館数芽
Kazume NISHIDATE Ph.D

Department of Systems Innovation Engineering,
Graduate School of Science and Engineering, Iwate University
4-3-5 Ueda, Morioka, Iwate, 020-8551 JAPAN
Phone:+81-19-621-6391
kazume.nishidate at gmail.com, nisidate at iwate-u.ac.jp
https://sites.google.com/site/nisidatelab/