LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Mailing List Archives
Re: [lammps-users] reax/c with eam
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [lammps-users] reax/c with eam


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Sun, 16 Jul 2017 15:20:27 -0400

On Sun, Jul 16, 2017 at 1:22 PM, Ray Shan <rshan@...1795...> wrote:
> Good point, Axel!  Reax/c uses real units and EAM metal units.  By using
> real units in a hybrid reax/EAM input, EAM is not building the frho list
> correctly.

that is a different story. the memory allocation fails with far too
large a number. frho allocation depends on parameters given in the
potential file and nothing else. that means, the potential file was
not correctly parsed, which in turn suggests, that the EAM potential
file is in the wrong format. if it was "only" in the wrong units,
LAMMPS would still be able to read it. only the results of the
simulations would be off.

i'm adding some checks to the EAM file reader routines, that will help
detect when people use an incorrectly formatted EAM potential file
like in this case. this will hopefully be included in the next LAMMPS
release.

as for the units, the lj/cut parameters are *very* suspicious, too.
they look like they were generated with a POOMA approach.

> You have to create an EAM potential file with real units for it to at least
> run.  The correctness of the hybrid reax/EAM model is another question.

yes, that is another serious concern. especially, since it doesn't
look like there was a significant amount of testing the model involved
here.

axel.

>
> Ray
>
>
> On Jul 16, 2017, at 10:10, Axel Kohlmeyer <akohlmey@...24...> wrote:
>
> On Sun, Jul 16, 2017 at 12:20 AM, Subodh Tiwari <sctiwari@...114...> wrote:
>
> Dear lammps users,
>
>
> I am trying to use reax/c with eam. I have 4 different type of atom treated
>
> with reax/c and 5th atom with eam potential. I am getting following error. I
>
> am not sure if this problem is memory related or some other issues. I am
>
> using ~300000 atoms on 1440 cores.
>
>
> "ERROR on proc 2: Failed to allocate 9731128776 bytes for array pair:frho
>
> (../memory.cpp:64)"
>
>
> Similar message from other processors as well. I am attaching my input file,
>
> forcefield. I couldn't attach datafile due to large size.
>
>
> how about creating a simple test input first to validate each part of
> your input?
> e.g. something like this?
>
> """
> units real
> region box block 0 10 0 10 0 10
> create_box 1 box
>
> create_atoms 1 single 5.0 5.0 5.0
>
> pair_style  eam
> pair_coeff  * * Pb_real.set
>
> run 0
> """
>
> ...and you will see, that this input cannot run. most likely because
> your eam potential file is bogus or not in the right format.
>
> no 300000 atoms on 1440 cores run needed to debug and fix. in general,
> it is *strongly* recommended (and common sense dictates it, too), to
> not start such a massive calculation without making small test runs on
> the individual components to validate their correctness. if you waste
> a few hours or days of computation on a desktop machine, no big
> problem, and debugging/testing is fast.
>
> axel.
>
>
>
> ------------------------------------------------------------------------------
>
> Check out the vibrant tech community on one of the world's most
>
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
>
> _______________________________________________
>
> lammps-users mailing list
>
> lammps-users@lists.sourceforge.net
>
> https://lists.sourceforge.net/lists/listinfo/lammps-users
>
>
>
>
>
> --
> 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.
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> lammps-users mailing list
> lammps-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/lammps-users
>
>
> ------------------------------------------------------------------------------
> Check out the vibrant tech community on one of the world's most
> engaging tech sites, Slashdot.org! http://sdm.link/slashdot
> _______________________________________________
> lammps-users mailing list
> lammps-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/lammps-users
>



-- 
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.