There are no 2nd derivatives in LAMMPS. I suppose

you could approx it by differencing, but there is no compute or

fix in LAMMPS currently that does that.

Steve

There are no 2nd derivatives in LAMMPS. I suppose

you could approx it by differencing, but there is no compute or

fix in LAMMPS currently that does that.

Steve

Trying writing a wrapper around the lammps. Calculate the energy using lammps, extract coordinate and energy information from lammps and then take taken second derivatives with respect to displacement (as you find appropriate) to calculate force matrix using finite difference approach.