lammps/tools/spin/interpolate_gneb

Interpolate.x tries to perform a cubic polynomial interpolation
of the MEP.  

Compile the program with:
gcc interpolate.c -o interpolate.x -lm -lgsl

and then run it as:
./interpolate.x

Enter N-1 (with N the number of replica).
The program reads the "neb_init.dat", in which you need to
replace the current values by your GNEB outputs.

Each line corresponds to a replica, and has to respectively
contain:

Reac. coords /tab/ pot. energy /tab/ fm dot tangent /tab/
geodesic dist to next replica

All those information can be provided by the verbose output of
a neb/spin calculation

The progam outputs the interpolation result, and the
interpolated MEP in "interpolation_result.dat". 

This code is a courtesy of Aleksei Ivanov, University of
Iceland.
For more explanation about this calculation, see Appendix D 
of the following reference:
Bessarab, P. F., Uzdin, V. M., & Jónsson, H. (2015). 
Computer Physics Communications, 196, 335-347.