Hello,
I tried to use tabulated potential with lammps.
To test the actual data used in lammps, I followed what is suggested in the
document.
First I built a table containing 276 data points of energy and forces
calculated from a Lennard-Jones 12-6 analytic function, called pot.lj.table
here.
(sigma=5.2 eps=1.0, r->[2.5, 30.0])
Then I use the following commands in my input script:
link,
This is a fairly common question. Take a look at some of the previous discussions on this topic in the archives:
https://sourceforge.net/search/?group_id=149493&words=table&type_of_search=mlists&pmode=0&limit=100
Also, you might want to take another look at the documentation:
http://lammps.sandia.gov/doc/pair_table.html
Make sure you use a large N in the table that you feed to LAMMPS (around 10000 should be good). Your 276 data points seems small to me. You're having LAMMPS do a cubic spline of the data you're feeding it, then a linear interpolation of the cubic spline data --- that's why it is non-linear.
As far as I know, the FPRIME keyword is not obsolete. It should work if formatted properly. Please make sure you're following the format procedures exactly as outlined in the documentation.
Paul