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Re: [lammps-users] units metal vs real -Reaxff
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Re: [lammps-users] units metal vs real -Reaxff


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Wed, 18 Oct 2017 10:15:16 -0400

On Wed, Oct 18, 2017 at 9:46 AM, Alexandra Davila
<davila@...6924...> wrote:
> Hi lammps-users,
>
> I have been calculating with reax force field some gold systems, I have
> always used units real.
>
> By error I did a calculation of the lattice with units metal, I was
> wondering why the output of the potential energy for both runs (with real
> and metal units) are the same. For real units energy should be printed in
> kcal/mol and for metal in eV, or with reax the default is real units (I
> think not)?

i think yes. the reaxff force field parameter files contain parameters
in real units.
so if you set units to metal in your input, they will be interpreted
as if they were in metal units instead, which may lead to all kinds of
funny behavior and outputs unless you convert the entries in the
parameter file to be in metal units as well (which is horribly tedious
to get done correctly)

axel.

>
> Probably I am making a very dummy mistake!
>
> I attach the *in file!
>
> thanks for the help!
>
> lammps version:  Stable version (11 Aug 2017)
>
>
>
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-- 
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.