Charge Density Corrected EAM in LAMMPS?

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1

Hi everyone,

I certainly hope i’m using this mailing list correctly! I’m freshly new to LAMMPS, so apologizes if this is a trivial question. I was wondering if it is possible to manually change the force equation that LAMMPS is using when using EAM.

In EAM, the force felt between neighbors is the following:

Force =

  • sum [ ( F_i(Rho) )’ * (Rho_®j)’ +
    ( F_j(Rho) )’ * ( Rho_i( r ) )’ +
    ( Phi_ij( r ) )’ ] * r^

In charge density corrected EAM, the force needs to be (b and c are constants):

Force =

  • sum [ ( F_i(Rho + B*|grad(Rho_i)|^2 ) + cRho_i)’ * (Rho_j)’ +
    ( F_j(Rho + B    |grad(Rho_j)|^2 ) + cRho_j)’ * (Rho_i)’ +
    (Phi_ij - 2c    Rho_i)’ ] * r^

I was reading the documentation and it states i should not just go and make changes to LAMMPS. How would i go about making this one change? Would it be best to make a completely new pairstyle as opposed to editing the EAM one?

Many thanks,
Michael

2

First, see if any of the EAM variants in LAMMPS
(there are some in the USER packages as well)
do what you want. If not, I suggest creating
a derived class e.g. PairEAMCharge and just
overriding the compute() function in it, as well
as whatever input methods are needed to
allow the user to input the additional params.

Then add some info to the eam doc page and
send the files to us, and we can add it to
the distro.

Steve