potential files

Hi lammps users,

How can I get potential files for different atoms?Is there any website to download potential files? For example I need rebo or airebo potential for specific atoms.
I appreciate your attention in advance,
Rostam

Hi lammps users,

How can I get potential files for different atoms?Is there any website to
download potential files?

there is no single, simple answer to this. it depends on the specific
potential type. for EAM type potentials, some links are provided in
the documentation, for many molecular force fields parameters can be
assigned with external tools and then the resulting files can be
converted to LAMMPS input/data files, for everything else, you have to
dig them up from the published literature.

For example I need rebo or airebo potential for specific atoms.

for those, you'll have to find the parameters in the literature or
generate them yourself.

axel.

Dear Rostam

Axel is correct. LAMMPS is not like other popular simulation MD
programs. You have to build the input files yourself, and manually
specify all of the force-field parameters yourself. Even if you know
what the parameters are (which can be difficult to locate), the
process of manually assigning them to the atoms in your molecule can
be tedious.

Both "moltemplate" and "topotools" can assign bonded (and non-bonded)
force-field parameters according to atom type. With moltemplate, you
can specify a file which contains the force-field parameters you want,
however you must create that file yourself. I created an example for
TraPPE (an extremely simple force-field). I am not familiar with all
of the many force-field types out there (and the different atomic
nomenclature used by each of them). I would need some help to add a
more complex or more popular force-fields to LAMMPS.

Anyway, the TraPPE example force-field is here:
http://www.moltemplate.org/examples/cyclododecane+watMW/trappe1998.lt

--------- Here is an excerpt from that file: ---------

TraPPE {

  write_once("Data Angles By Type") {
    @angle:backbone @atom:CH? @atom:CH? @atom:CH? @bond:saturated
@bond:saturated
  }

  write_once("Data Dihedrals By Type") {
    @dihedral:backbone @atom:CH? @atom:CH? @atom:CH? @atom:CH?
@bond:saturated @bond:saturated @bond:saturated
  }

  # Note: The "?" is a single-character wildcard character. ("*" also works.)

  write_once("In Settings") {
    pair_coeff @atom:CH2 @atom:CH2 lj/charmm/coul/charmm 0.091411522 3.95
    pair_coeff @atom:CH3 @atom:CH3 lj/charmm/coul/charmm 0.194746286 3.75
    pair_coeff @atom:CH4 @atom:CH4 lj/charmm/coul/charmm 0.294106636 3.73
    bond_coeff @bond:saturated harmonic 120.0 1.54
    angle_coeff @angle:backbone harmonic 62.0022 114
    dihedral_coeff @dihedral:backbone opls 1.411036 -0.271016 3.145034 0.0
  }

} #TraPPE