[lammps-users] pair coeffs error with setting up SAM-Au simulation

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1

Hi, I modified the input file and get a different but similar error:

pair_style lj/cut 2.5
bond_style harmonic
angle_style harmonic

read_data data.SAM-Au

pair_style hybrid eam morse 2.5 lj/cut 2.5
pair_coeff 1 1 eam Au_u3.eam
pair_coeff 1 2 morse 0.1378 0.01477 2.56 2.5
pair_coeff 2 2 lj/cut 4.250 1.6629 2.5
pair_coeff 3 3 lj/cut 3.905 0.495 2.5
pair_coeff 4 4 lj/cut 3.905 0.7325 2.5

and the error changed into: ERROR on proc 0: All pair coeffs are not set

I debuged the code with visual studio and this error comes from
pair_hybrid.cpp::init_one, in which map[i][i][0] != map[j][j][0], it
seems they have value 0 and 2 respectively.

Thanks for any hints!

Best
Xiaoyin Ji

2

From: xiaoyin ji <[email protected]...>
Date: Wed, Jan 20, 2010 at 6:28 PM
Subject: Re: [lammps-users] pair coeffs error with setting up SAM-Au simulation
To: Axel Kohlmeyer <[email protected]>

Hi, I modified the input file and get a different but similar error:

pair_style lj/cut 2.5
bond_style harmonic
angle_style harmonic

read_data data.SAM-Au

pair_style hybrid eam morse 2.5 lj/cut 2.5
pair_coeff 1 1 eam Au_u3.eam
pair_coeff 1 2 morse 0.1378 0.01477 2.56 2.5
pair_coeff 2 2 lj/cut 4.250 1.6629 2.5
pair_coeff 3 3 lj/cut 3.905 0.495 2.5
pair_coeff 4 4 lj/cut 3.905 0.7325 2.5

and the error changed into: ERROR on proc 0: All pair coeffs are not set

and rightfully so. you have not specified coefficients for all pairs.

where are the interactions for
1-3, 1-4, 2-3, 2-4, 3-4??

BTW. there is more trouble down the road for you.
you were using "real" units, but eam _requires_ "metal" units (unless you
converted the eam file). also your cutoffs for LJ seem very strange
(2.5 Angstrom?) same goes for sigma and epsilon. what units are those in?

I debuged the code with visual studio and this error comes from
pair_hybrid.cpp::init_one, in which map[i][i][0] != map[j][j][0], it
seems they have value 0 and 2 respectively.

actually the error comes from your input.

cheers,
     axel.

3

Hi Axel,

Thanks for your reply. I'm still working on the parameters...other
interactions are supposed to be taken care of by harmonic bond and
angle potentials. So if I just define lj/cut for each atom type, this
input file works. However my system requires eam for Au and morse for
Au-S interaction.

What if I never need the potential for, 1-3..etc?

Thanks

Best
Xiaoyin Ji

4

Hi Axel,

Thanks for your reply. I'm still working on the parameters...other
interactions are supposed to be taken care of by harmonic bond and
angle potentials. So if I just define lj/cut for each atom type, this
input file works. However my system requires eam for Au and morse for
Au-S interaction.

well, that reminds me, you should take note, that this kind of model
has some limitations. the surface reconstruction can be quite complicated.
you may want to have a look at, e.g.,http://dx.doi.org/10.1126/science.1158532

What if I never need the potential for, 1-3..etc?

have you seen pair_style none?

axel.

5

"Pair style hybrid cannot have none as an argument". It seems there
are more work to be done. Thanks for your advise!

Best
Xiaoyin Ji

6

"Pair style hybrid cannot have none as an argument". It seems there
are more work to be done. Thanks for your advise!

if you use lj/cut and specify as pair_coeff epsilon=0.0
you should get the same as with pair_style none.

axel.

7

pair_style hybrid lj/cut ... sw ... etc
pair_coeff 1 2 none

Please read the pair hybrid doc page - it discusses
this.

Steve