Steve,

Thanks for your reply.

I have a CNT. I hold a few rings of CNT atoms at the right end (groupRight) using fix setforce 0 0 0. I then apply fix move linear to some rings of atoms on the left end (groupLeft)

Will “compute groupRight reduce sum fx” and “compute groupLeft reduce sum fx” both give the tensile force?

I’m just looking for the tensile force in the CNT.

Thanks very much

Daniel

Steve,

Thanks for your reply.

I have a CNT. I hold a few rings of CNT atoms at the right end

(groupRight) using fix setforce 0 0 0. I then apply fix move linear to some

rings of atoms on the left end (groupLeft)

Will "compute groupRight reduce sum fx" and "compute groupLeft reduce sum

fx" both give the tensile force?

like the documentation says, compute reduce sum will sum up the per

atom property across all atoms in that group. whether this is the

force you are looking for depends on your overall setup. you can

usually resolve this with some simple classical mechanical

considerations on a piece of paper.