I am studying the lammps manual for conversion for Tersoff potential formula 1 (lammps’s Tersoff_1) [PRB37,6691’88] and formula 2 (lammps’s Tersoff_2) [PRB39,5566’89] and still wonder about its f_c(r_ij) form are different and may not be easily converted each to other. Shorly 1st is 1/2-1/2sin(Pi/2(r-R)/D) but 2nd 1/2+1/2cos(Pi(r-R)/D).
I am asking that since I found some potential which are in either forms. Couls you make some more clarification.
Any help could be appreciate with courtesy…
Maybe Aidan can answer this, I've CCd him.
I think they are the same, but the intervals are different.
1/2+1/2 sin(Pi/2 (r-R)/D) R-D<r<R+D
is equal to
1/2-1/2 cos(Pi (r-R')/(S-R')) R'<r<S ; R'=R-D , S=R+D
Steve Plimpton wrote:
I don't understand your question(s), so let me ask you one. Have you tried
using the formulas given in the LAMMPS documentation to convert?
R=(R'+ S')/2 and D=(S'- R')/2