[lammps-users] Problem on Stress!

Dear Lammps_users

    I apply a velocity on one end of nanowire with another end fixed.
      I creat a group including the middle section of the nanowire.
      During the process, I dump the stress (the group created) and
      I find some stress is positive, while the other is negative.
       
      I am puzzled by this. I have thought all the stress should come out with
      the same sign under this load.

      Is there some possible reason for this?

Best Regards

Zhenyu Yang
  State Key Laboratory of Nonlinear Mechanics (LNM)
  Institute of Mechanics, Chinese Academy of Sciences
  No.15 Beisihuanxi Road
  Beijing 100080, P. R. China
  FAX: 010-62579511
[email protected]
2006-07-11

Stress (like pressure) has big fluctuations. It's not surprising
to me if you yank on a wire, that you will see +/-
oscillations in the stress on individual atoms over time ...

Steve