Hi Ravula Sai Charan Use,

compute group/group : https://docs.lammps.org/compute_group_group.html

or,

compute tally: https://docs.lammps.org/compute_tally.html

depending if you want to sum over effects.

and dump results using the dump command: https://docs.lammps.org/dump.html

Israel Zadok Thank you so much for your reply Sir .If you have example input lammps code related to this can you please share with me?

compute f1 poly CH2 force/tally BOR

variable fx equal c_f1[1]

variable fy equal c_f1[2]

variable fz equal c_f1[3]

fix ff poly ave/correlate 1 100 100 c_f1[1] c_f1[2] c_f1[3] type auto file force.dat ave running

I written these lines to extract force but im getting error

ERROR: Unrecognized compute style 'CH2' (src/modify.cpp:1282)

Last command: compute f1 poly CH2 force/tally BOR

where I did mistake Can you please help me out.