Incorrect args for pair coefficients (../pair_eam_fs.cpp:52)

Dear LAMMPS users,

When trying to simulate bcc Fe with C on an interstitial site (so, 2 atomic types only) with the following lines:

Dear LAMMPS users,

When trying to simulate bcc Fe with C on an interstitial site (so, 2 atomic
types only) with the following lines:

#---------------------------
pair_style eam/fs
pair_coeff * * Fe-C_Hepburn_Ackland.eam.fs Fe C
#---------------------------

I got an error stopping at the above spot in the log file:

#--------------------------------------
pair_style eam/fs
pair_coeff * * Fe-C_Hepburn_Ackland.eam.fs Fe C
ERROR: Incorrect args for pair coefficients (../pair_eam_fs.cpp:52)
#---------------------------------------

Of course if I defined only Fe here:
#-----------------------------------------
pair_coeff * * Fe-C_Hepburn_Ackland.eam.fs Fe
#-----------------------------------------
it went through until reaching an invalid atomic type 2 later in my script.

well, *this* is your real problem. it looks as if you reserved only
space for a single atom type when creating the simulation box. then
you cannot have more atom types. the eam/fs pair styles requires a
number of arguments that is commensurate with the number of atom
types. as soon as the simulation box is created in LAMMPS, the number
of atom types and several other properties are committed and cannot be
changed anymore.

axel

Hi Axel,

I tried it with a bcc lattice with a 4-site motif, one for Fe and three as the octahedral vacancies reserved for C. But I got the same error message with pair_coeff.

Could you elaborate some more, or give an example, on how to write commensurately with the eam/fs format? Your help is appreciated.

Jiayi Yan
Materials Science, KTH, Sweden

Hi Axel,

I tried it with a bcc lattice with a 4-site motif, one for Fe and three as the octahedral vacancies reserved for C. But I got the same error message with pair_coeff.

Could you elaborate some more, or give an example, on how to write commensurately with the eam/fs format? Your help is appreciated.

This has nothing to do with eam/fs or the lattice. I already told you, that the problem happens due to reserving space for only one atom type when creating the box. Please read the documentation more carefully and don’t make me tell you the same thing a third time…