Hi Everyone,
I got the February 2012 package the other day to start working on fitting an ADP style potential. From the “pair_style adp” manual page, I read…
"Following the Nelements sections, Nr values for each pair potential phi® array are listed for all i,j element pairs in the same format as other arrays. Since these interactions are symmetric (i,j = j,i) only phi arrays with i >= j are listed, in the following order: i,j = (1,1), (2,1), (2,2), (3,1), (3,2), (3,3), (4,1), …, (Nelements, Nelements).
After the phi® arrays, each of the u® arrays are listed in the same order with the same assumptions of symmetry. Directly following the u®, the w® arrays are listed."
… and so I wrote a script to generate an input file with tabulated F(rho), rho®, phi®, u®, w®, etc. It soon became clear that something was wrong, and I recalled that in pair_style eam/alloy, for example, r*phi® is tabulated instead of phi®. I made the change and things worked closer to my expectations. I also compared some of the ADP potentials that came with the LAMMPS distribution and plots of phi®, u®, etc. in the corresponding journal papers and they matched.
So it seems to me that the ADP file format uses F(rho), rho®, r*phi®, u®, w®, etc. In other words, phi® is the only function scaled by ®. Can someone else verify this for me? Also, if this is correct, might I suggest adding the line…
“The tabulated values for each phi function are listed in setfl files directly as r*phi (in units of eV-Angstroms), since they are for atom pairs.”
… from the “pair_style eam/alloy” manual page to the “pair_style adp” manual page? This would perhaps save someone else some confusion.
Thanks for your consideration and to all the LAMMPS developers for their hard work.
Jason Gruber