[lammps-users] effective charge function Z(r) in EAM potential

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1

Dear all lammps users

as the pair wise pair interaction energy phi(eV) is given as a function of r_ij(Angstroms).
But in lammps The units for the effective charge Z are “atomic charge” or sqrt(Hartree * Bohr−radii) as given in manual. and the unit is eV-Angstroms. As per the manual
For 2 interacting atoms i,j this is used by LAMMPS to compute the pair potential term in the EAM energy expression as rphi, in units of eV−Angstroms, via the formula
rphi = 27.2 * 0.529 * Zi * Zj
As in the first line its written as sqrt(Hartree * Bohr-radii), where as in the second line it’s simply multiplied r*phi.
I just wanted to know what exactly LAMMPS required for the pair wise interaction eneergy term for EAM potential file. I am having phi(eV) vs r_ij(Angstroms) curve as an input. In that what conversion is required to get the effective charge Z (eV-ngstroms). If any one can tell me I’ll be thankful to them.

warm regards

Vijay

2

I would look in pair_eam.cpp and one of the existing EAM potential
files and plot the values and see if they are what you expect. The
conversions to LAMMPS internal units (energy, force, etc) as on
the units doc page are done in pair_eam.cpp. These units go back
to the convention in the original EAM codes as created by the EAM
inventors.

Steve