[lammps-users] nve working npt not

Hi all,

i use nve with a temp/rescale and everything works fine. The thing now is that i want to control pressure too.
so i change to npt all of a sudden i am getting after some steps nan and zeros at temp press etc. Any idea why is this happening?
The rest of the file is the same.

fix 1 adsorbents rigid single
fix 2 adsorbents setforce 0.0 0.0 0.0
fix 3 particles nve
fix 4 particles temp/rescale 100 300.0 300.0 10.0 1.0

VS

fix 1 adsorbents rigid single
fix 2 adsorbents setforce 0.0 0.0 0.0
fix 3 particles npt temp 300.0 300.0 100.0 iso 1.0 1.0 100.0

Try using NVT instead of NVE along with temp/rescale to equilibrate the temperature first.

2010/6/15 Jim Jim <drazentl@…8…>

NVT with temp/rescale? If i use NVT only temperature won’t be fixed?
And after should i use the npt?

Still the same. Temperature’s output is zeros. and when npt nan.
Lammps manual says that we should nt use temp/rescale along with nvt integrator.

Could be a number of things. I would try turning off
fix rigid. If you set the force on those atoms to
0 and their velocities to 0, they won't move. Or just
don't integrate them with npt. You should not use
fix nvt with fix temp/rescale. That is double thermostatting.

Steve

2010/6/15 Jim Jim <[email protected]...>:

I tried to do what you suggest me but again i take Temp =0.0 and for pressure the same . I used nvt alone and again the Temp stays zeroes.

Dear Jim, could you post the plot of total energy (NVE with temp/rescale). Do you see any anamolies there? Does the total energy in case of NVE close to what you should expect?
Try printing data in NPT every timestep and see the trend. That could tell you a lot. Try dumping the coordinates every timestep and visualize the results.