I am using NPH simulations and found your post at

I have tried your script and have several questions as following:

  1. The trajectory of the system is independent of the setting of:
fix_modify      nph energy yes

Which means the setting above only effect the output of potential energy, but not the dynamics (or properties) of the system. Is it correct?

  1. I have noticed you set pchain=0 with fix nph. Could you please tell me why it is necessary? Should “fix nph” exclude thermostat by default?

  2. What are the physical meanings of the following variables in your script:

f_nph f_nph[1] f_nph[2] f_nph[3] f_nph[4]

how many terms are there in f_nph? Where can I found those information?

Thank you very much for your help.