[lammps-users] question for NVT

You must be doing something else in your script. Try setting
the initial temp to 300 with the velocity command. You don't
say what units you are using, but probably metal. That means
your damping constant for fix nvt is 10- psec, or about 100K timesteps
which is far too long. Try a damping constant of 0.1

Steve

2009/3/26 弓晓晶 <[email protected]...>:

Dear all,
       Thank you for Steve Plimpton’s reply.
       However there are still some problems about NVT: I have used the
following commands to constrain T at 300K.
velocity bloque create 300.0 4928459 dist gaussian
      fix bloque all nvt 300.0 300.0 1 ; (damping coeffient also use as 1)
     
or
velocity bloque create 300.0 4928459 dist gaussian
velocity bloque scale 300.0
fix bloque all nvt 300.0 300.0 1 ; (damping coeffient also use as 1)

However the temperature in the log file is not about 300K:
Step Temp E_pair E_mol TotEng Press
0 300 -5663.932 0 -5610.9224 255442.6
1000 499.85246 -5578.8617 0 -5490.5385 286534.59
2000 179.64753 -5633.941 0 -5602.1975 264730.9
3000 337.02219 -5599.4396 0 -5539.8882 277939.28
……..
998000 171.43345 -5780.4513 0 -5750.1592 232124.62
999000 451.14671 -5728.0205 0 -5648.3035 248360.84
1000000 196.27061 -5772.8096 0 -5738.1289 234447.95

I am sorry for always asking the trival question, but the time controlling
is important for the simulation, so I will appreciate it if you can help me.

Regards
Xiaojing
  
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