Dear Lammps users,
I’m trying to stretch a polymer molecule in LAMMPS. I would like to fix one end atom, but it didn’t work.
First I fixed the one end atom by following commands:
fix 0 bottom setforce 0.0 0.0 0.0
velocity bottom set 0.0 0.0 0.0
And then apply a force on the other end atom by:
fix 1 rightend addforce 0.0 0.0 800.0 every 1
Output the position of 2 end atoms by fix print:
fix writeX boundary print 1 “{posX0} {posY0} {posZ0} {posX} {posY} {posZ}” file position.txt screen no
I have tested it by running lmp_mpi on my personal computer with lammps/2020-10-29 for short time, and it did work. Then I run it (still with lmp_mpi) on a supercomputer with lammps/2015-08-10 to do a long run. However, the expected fixed atom moved. Could you please give any suggestions if you have ever known this problem before? I highly appreciate your time and help.
Thank you very much.
Best regards,
Yanxia
ETH Zurich