# [lammps-users] nvt and relax time

Lu H.Q. wrote:

Dear all

i have had a puzzle on relax time.now i want simulation the
solidification of the metal melt droplet, i used fix nvt command like
this :

units metal
................
velocity all creat 2300 32545
................
fix 3 all nvt 2000 300 100
.....................
timestep 0.1
run 1000

Then my question is

a. In order to get the melt of metal , i set the temperature 2300
above the melt point of metal in the velocity command ,then
equilibrated in this temperature for a special time by fix nve (run
1000 timestep),is it right or valid?

b. how shoud the random seed "32545" be set? is it arbitrary ? what is
considered when it did.

c in simulation solidification process (fix 3 all nvt 2300 300
100), if i can get the temperature each timestep is a ramped value
during the run (1000) from (2300)to (300), that is we got
2298,2296,2294,2292,2290........306,304,302,300

I think you can decrease the Tdamp to decrease the fluctuation of temperature, or use the drag option.
In my simulation, Tdamp is twenty times of timestep