Dear Lammps users,
I am confused that the velocity command and fix nvt command affect each other.
The simplified input file is
fix 1 all nvt temp 0.02 0.02 0.5
velocity group-1 set 0.1 0 0
velocity group-2 set -0.1 0 0.
In this file, atmos in group-1 and group-2 will collide.
And, I consider that the impact velocity is 0.1+0.1=0.2 in this calculation.
However using this file, the velocity of group-1 is 0.16 0 0, and that of group-2 is -0.16 0 0, so that the impact velocity becomes 0.32.
I check some archives, and I found that the damping of thermostat affects the velocity of the groups.
But there is no explanation that the initial velocity varies.
Also, the velocity varies, getting bigger and smaller.
My question is “Is there any relation between fix command and velocity command?”, also “How do they affect each other?”.
Or, is my question fundamentally wrong?