[lammps-users] Use SW and AIREBO in a single run

Dear all lammps users,

I am doing some simulation about Silicon and Carbon. I think the Stillinger-Weber potential and AIREBO potential should be used for Si and C, respectively. However, even if a pair_style hybrid command is used, the Manual still tells me that:

pair_coeff * * CH.airebo C C C H
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.

pair_coeff * * SiC.sw Si Si Si C
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.

So I wonder the two * * may cause some confliction to specify the atom type. Is there any solution? or I have to change to another potential?

Thanks in advance.

Best Regards,

Feng-Chao Wang

2010-07-14

2010/7/13 Fengchao Wang <[email protected]>:

Dear all lammps users,

I am doing some simulation about Silicon and Carbon. I think the
Stillinger-Weber potential and AIREBO potential should be used for Si and
C, respectively. However, even if a pair_style hybrid command is used, the
Manual still tells me that:

are you sure this is a reasonable choice?
have you checked whether there are any
examples in the literature that use this kind of setup?

even for pairwise additive potentials, mixing and matching
different potential types or parametrizations is generally
frowned upon unless there is a good physical justification.

both stillinger-weber and AIREBO are manybody
potentials, i.e. not pairwise additive. by mixing those,
you add all kinds of inconsistencies to your system.

why not stick to the SiC.sw potential which supports
both Si and C.

pair_coeff * * CH.airebo C C C H
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
pair_coeff * * SiC.sw Si Si Si C
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.

So I wonder the two * * may cause some confliction to specify the atom type.
Is there any solution? or I have to change to another potential?

you have to read the documentation more carefully as it explains
how you match the numbered atom types in LAMMPS to the labeled
types in the potential files. for pair hybrid you have the NULL option
to skip a type that should not be represented by a given manybody
potential.

axel.