unavailability of NEB command

Dear LAMMPS developers,

I am using the LAMMPS code for studying ionic systems. Recently, I was trying to calculate the activation barrier of my system in LAMMPS and I ran into to some problems. I am hoping that you can provide me with some pointers to sort out this problem.

I am using latest LAMMPS version . I am using the following command as mentioned in the LAMMPS manual:

fix NEB oxy neb 0.5
neb 0.000000001 0.001 1000 1000 1000 cord.final

But for fix neb command it shows the error " Invalid fix style (modify.cpp:647)" and for neb command it shows the error “Invalid command”. I also checked all lammps source codes but i didnt find any neb command there. Even in latest version of LAMMPS i didnt find anything about neb.
I thank you very much for your kind consideration of my query and eagerly look forward to your response.
Harshal Mathurkar

Harshal, did you include the NEB package before you compiled LAMMPS? It is on optional package and isn't included by default. See the LAMMPS manual for including optional packages.

Thomas O'Connor
Physics & Astronomy
Johns Hopkins University

It seems you didn't have REPLICA package installed. Please see


The package is called REPLICA.
Type 'make yes-REPLICA' in lammps/src and rebuild.