NPT temperature

Hi, all lammps users, I am simulating a doubled Wall CNTs, but the inner CNT is fixed ( setforce is 0 and velocity is 0). While I fix the outside CNT under NVT for 300K and NVE the CNT outside can maintain at 300K. But as I fix the outer CNT in NPT, the temperature blows up around 500K. I am not sure what's wrong with that? Since previously I already fixed the coefficients, the structure is fine. Thanks.

the NPT command is below:

fix NPT cntoutside npt temp 300 300 100.0 x 1.0 1.0 1000.0 y 1.0 1.0 1000.0 z 1.0 1.0 1000.0
run 100000

Haoxiang

Hi, all lammps users, I am simulating a doubled Wall CNTs, but the inner CNT is fixed ( setforce is 0 and velocity is 0). While I fix the outside CNT under NVT for 300K and NVE the CNT outside can maintain at 300K. But as I fix the outer CNT in NPT, the temperature blows up around 500K. I am not sure what's wrong with that? Since previously I already fixed the coefficients, the structure is fine. Thanks.

the NPT command is below:

fix NPT cntoutside npt temp 300 300 100.0 x 1.0 1.0 1000.0 y 1.0 1.0 1000.0 z 1.0 1.0 1000.0
run 100000

this is far too little information to make sense of your description.

and generally asking, why do you need to run with fix npt for an
isolated object in the first place?

axel.