How to plot dU/dλ wrt λ after getting fep output file

Dear all,

lammps version - 29 oct 2020

I have done a simulation of a water droplet on a graphite surface the main objective was to find out the free energy difference between the initial and final configuration using the FEP module. Now I want to plot a curve between du/dλ and λ. How can I extract the data points from the final output file is what I am trying to figure out. From the code which is given in the lammps example folder I am able to calculate the value of the free energy difference of the system. Any help regarding how to generate the data sets to get a proper plot would be much appreciated.

Thank you,


I don’t think the USER-FEP author has joined the forum yet. So you should look for an answer on the mailing list (which will also eventually show up here in the mailing list archive).

Please be considerate when asking questions on the weekend. Many people have families and a life outside of science and thus can not always reply instantly. I would recommend to wait at least two business days before repeating the question.