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Re: [lammps-users] Error: All pair coeffs are not set
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Re: [lammps-users] Error: All pair coeffs are not set


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Tue, 18 Jul 2017 15:12:19 -0400

On Tue, Jul 18, 2017 at 12:26 PM, yang hong <yang@...7001...> wrote:
> Hello all,
>
>
>
> I am trying to use a hybrid/overlay pair style to describe a system
> containing a carbon nanotube, a carbon wall and water molecules with SPC/E
> model as well as some salt ions.

there is not need for hybrid/overlay. this should work with pair style
hybrid (which is much safer to use).

> I would like to use CH.airbo for carbon wall and the rest of the system with
> lj/cut/coul/long.
>
> I mentioned the pair coefficients for all atomic types (including the carbon
> wall) in the data file by Pair Coeffs section.

it is a really, really bad idea to have the the lj/cut/coul/long
specified multiple times.
just once will do.

including the carbon ones is a very bad idea, since that will compute
those interactions twice (due to using hybrid/overlay and not hybrid).

> /////////////////////////
>
> Pair Coeffs
>
>
>
> 1 lj/cut/coul/long 1 0.003725 3.3997
>
>  2 lj/cut/coul/long 2 0.00199475 2.985
>
> 3 lj/cut/coul/long 3 0.00130526 2.42
>
> 4 lj/cut/coul/long 4 0.0067366 3.166
>
> 5 lj/cut/coul/long 5 0.0000 0.0000
>
> 6 lj/cut/coul/long 6 0.00730252 2.2589
>
> 7 lj/cut/coul/long 7 0.00050736 5.1645
>
> 8 lj/cut/coul/long 8 0.003725 3.3997
>
[...]

>
> And I mix the pair coefficients with pair modify in the input file.

...and that is your problem. with your setup, you prohibit mixing.
at any rate, you cannot have mixing between the AIREBO interactions
and the lj/cut/coul/long ones.
so all mixed interactions for those pairs *must* be given explicitly.

those are actually easy to obtain in your case with LAMMPS commands.
just run your regular input w/o airebo and then use the write_coeff
command, to convert the per-type parameters into mixed per-pair data
and then edit the result into your hybrid input (and delete the Pair
Coeffs section in the data file).


>
>
> ///////////////////////////
>
> pair_style              hybrid/overlay lj/cut/coul/long 9.8 lj/cut/coul/long
> 9.8 lj/cut/coul/long 9.8 lj/cut/coul/long 9.8 lj/cut/coul/long 9.8
> lj/cut/coul/long 9.8 lj/cut/coul/long 9.8 lj/cut/coul/long 9.8 airebo 3.0 0
> 0

see my comment above. this is not a very smart way to specify the
hybrid system. it *must* work with
pair style hybrid lj/cut/coul/long 9.8 airebo 3.0  1 1

[...]

> Then I got an error and a warring massage like:
>
>
>
> WARNING: Using a manybody potential with bonds/angles/dihedrals and
> special_bond exclusions (../pair.cpp:218)

that is a serious problem. you have to remove
bonds/angles/dihedrals/impropers for the atoms that you want use with
pair style airebo. in airebo, all of these interactions are implicit
and recomputed on the fly (it is a reactive manybody potential, and
not a class 1 classical MD force field)

>
> ERROR on proc 0: All pair coeffs are not set (../pair_hybrid.cpp:573)

yes. you are missing the mixed coeffs, since your pair style input
disallows any mixing.

> This simulation runs well when I use lj/cut/coul/long pair style for all
> atomic types.
>
>
>
> Thanks for any help.

you have a lot of work to do. there are many corrections needed.

axel.

>
>
>
> Best,
>
>
>
> Yang
>
>
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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.