[QE-users] can i use this trick to do faster MD calculation using pw.x ?

[Jayraj Anadani]

Thank you for your response.

On Wed, Oct 18, 2023 at 6:59 PM Kazume NISHIDATE <nisidate at iwate-u.ac.jp>
wrote:

> Dear Jayraj;
>
> > the temperature fluctuations are too high compared to the other
> >  literature.
>
> Because you are using "thousands of atoms" in LAMMPS while you are using
> only the 128 atoms in QE.
>
> > MD simulation of thousands of atoms in LAMMPS
> …….
> > On my metallic system, which has 128 atoms,
>
>
> You must understand the concept of ensemble average.
> A good text was introduced by Nicola:
>
> > 3) not sure where to start - you need to learn and understand MD - a
> >  good start is if you google "ercolessi md primer"
>
>
> In addition to his elemental comments, I want to add some trivial
> things.
>
> > "conv_thr" (i.e. ecutwfc=5 or 10) below a minimum cutoff of
> >  pseudopotential? So that I can get the next ionic position very
>
> Suppose you have a potential curvature having a shape like a cup and
> a ball is falling along its curvature from its edge. The ball will
> perform oscillating behavior continually if there is no energy loss by
> a friction (energy conservation).
>
> In a primitive molecular dynamics calculation (MD), total energy
> (kinetic+potential) must be preserved in the long time scale (say
> 10000 time steps) when the system does not have a restriction on its
> kinetics (like temperature regulation).
>
> The "ecutwfc=5" apparently insufficient to evaluate the potential
> curvature and hence your MD calculation will collapse. It is
> equivalent to a MD in LAMMPS with random interaction potentials.
>
> Use the default cutoff energy and monitor the fluctuation of total
> energies in the MD runs with changing the dt (time increment value) to
> find the appropriate (largest) dt with preserving the total energies.
>
> And you can also consider a gamma-point only calculation if your
> system is large enough.
>
>
>
> 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/
>
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20231018/2c613003/attachment.html>