[QE-users] Atomic velocities units

Tue Aug 10 11:39:20 CEST 2021

The velocities are both printed in any place, but it is not the first time
I get this request, maybe it could be added in the future. That said, they
are trivial to compute v(t)=(r(t-1)-r(t))/dt

-- 
Lorenzo Paulatto

On Tue, Aug 10, 2021, 01:44 valeria arteaga muñiz <valitzelar at hotmail.com>
wrote:

> Hello Lorenzo,
>
>
>
> Thank you again. I don’t know how could I fix that bug since the version
> of QE I am currently using is installed on a supercomputer, and I don’t
> think I have access to the main directories.
>
> Another question; is there a way to grep or look for the velocities in
> some kind of output file from a pw.x run?
>
>
>
> Thanks,
>
> Valeria
>
>
>
> *From: *Lorenzo Paulatto <paulatz at gmail.com>
> *Sent: *Tuesday, August 3, 2021 3:17 PM
> *To: *Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject: *Re: [QE-users] Atomic velocities units
>
>
>
> It is a trivial fix, but I'm away from my pc for a couple of weeks. It is
> fixed in my gitlab fork
>
>
>
>
> https://gitlab.com/paulatz/q-e/-/commit/2c1e1d3d8b5c47639ba1af3842d187d5903115c5
>
>
>
> --
> Lorenzo Paulatto
>
>
>
> On Mon, Aug 2, 2021, 17:18 valeria arteaga muñiz <valitzelar at hotmail.com>
> wrote:
>
> Thank you both for your replies.
>
> Okay, I will take that into consideration. Actually I wanted to use the
> atomic velocities together with the svr thermostat, do you suggest any
> other method since that one doesn't work well with the atomic velocities?
>
> Best,
>
> Valeria
>
> Valeria
>
>
>
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Paolo Giannozzi <p.giannozzi at gmail.com>
> *Sent:* Monday, August 2, 2021 8:47:07 AM
> *To:* Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
> *Subject:* Re: [QE-users] Atomic velocities units
>
>
>
> From a quick look at the code, it seems to me that the documentation is
> correct for both pw.x and cp.x. For cp.x,  the velocities are given with
> the same logic as for the atomic positions (in A, Bohr, units of lattice
> parameter, crystal units) divided by time in hartree a.u. (2.4189*10^-17 s)
> ; for pw.x, the velocities are always given in Bohr divided by Rydberg a.u.
> for time (4.8378*10^-17 s). I am rather puzzled by the cp.x logic, but this
> is how it works right now
>
>
>
> Paolo
>
>
>
> On Fri, Jul 30, 2021 at 3:07 PM Lorenzo Paulatto <paulatz at gmail.com>
> wrote:
>
> I'm not sure, actually the time conversion I gave you is for pw.x, as cp.x
> use Hartree units instead of Rydberg for the energy there is a possible
> factor 2 difference (the base to find out this conversion is keep in mind
> that [ħ]=J·s=1 in atomic units.
>
>
>
> The input manual says that pw.x velocities are just "atomic units", no
> conversion is done in the code as far as I could see.
>
>
>
> Also keep in mind that ATOMIC_VELOCITIES is a seldom used feature, and may
> have bugs (i.e. I recently found out that it does not work with svr
> thermostat because of a little bug)
>
>
>
> hth
>
>
>
> --
> Lorenzo Paulatto - Paris
>
> On Jul 29 2021, at 8:17 pm, valeria arteaga muñiz <valitzelar at hotmail.com>
> wrote:
>
>
>
> Hello Lorenzo,
>
>
>
> Thanks for your reply. This is also for the pw.x code, right?
>
>
>
>
>
>
>
> Best,
>
>
>
> Valeria
>
>
>
>
>
>
>
> *From: *Lorenzo Paulatto
> <https://link.getmailspring.com/link/17A87165-F0AB-4C7C-9C86-AEE21336990C@getmailspring.com/0?redirect=mailto%3Apaulatz%40gmail.com&recipient=dXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%3D>
>
> *Sent: *Thursday, July 29, 2021 11:18 AM
>
> *To: *Quantum ESPRESSO users Forum
> <https://link.getmailspring.com/link/17A87165-F0AB-4C7C-9C86-AEE21336990C@getmailspring.com/1?redirect=mailto%3Ausers%40lists.quantum-espresso.org&recipient=dXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%3D>
>
> *Cc: *users at lists.quantum-espresso.org
> <https://link.getmailspring.com/link/17A87165-F0AB-4C7C-9C86-AEE21336990C@getmailspring.com/2?redirect=mailto%3Ausers%40lists.quantum-espresso.org&recipient=dXNlcnNAbGlzdHMucXVhbnR1bS1lc3ByZXNzby5vcmc%3D>
>
> *Subject: *Re: [QE-users] Atomic velocities units
>
>
>
>
>
> It depends on which units you have specified for atomic positions.
> Regarding time,
>
> 1 a.u.=4.8378 * 10^-17 s
>
>
>
>
>
> kind regards
>
>
>
>
>
> --
>
> Lorenzo Paulatto - Paris
>
> On Jul 29 2021, at 5:20 am, valeria arteaga muñiz <valitzelar at hotmail.com>
> wrote:
>
>   Hello everyone. I am trying to perform a MD run using the pw.x code. I'd
> like to use the atomic positions and also velocities from another run in
> Angstroms and Å/picoseconds to the QE input, but I am not sure about the
> units I need to use. In the documentation, there says it should be atomic
> units, and when I read the co.c documentation it was the same, but in the
> description they mentioned we needed to use the units as they're in the
> atomic positions card and time in a.u. does anyone have an idea of what
> convertion should I use?
>
> Thanks for your time
>
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>
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>
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> _______________________________________________
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>
>
> --
>
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _______________________________________________
> 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
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>
> _______________________________________________
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