I wasn’t sure how to reply to my original question so sorry if I responded incorrectly. Steve Plimpton replied to my original question with the same title of this email and I’m following up to clarify.
I believe that the two equations are different from looking at them. The equations are listed below:
E = Sum(n=0,n) Ancos[nphi] Eqn. (1) From the paper.
E = Sum(n=1,n) An*cos^(n-1)[phi] Eqn. (2) From lammps.
Now if I do the series expansion for a few terms…
(1) E = Ao + A1cos[phi] + A2cos[2phi] + A3cos[3*phi] + …
(2) E = A1 + A2cos[phi] + A3cos^2[phi] + A4*cos^3[phi] + …
Based on how the equations are set up, this is what I believe the series expansion would be. Observing these two expansions it would seem like they are different to me unless I’m incorrect on the expansions.
University of Colorado Colorado Springs