[lammps-users] Doubt about output pressure

Hi all

I have some doubt about the pressure of my system. I minimized my stem
and then ran the NVE. The initial density of the system is equal to
the real density at 1 atmosphere. The output looks like:

Step Temp E_pair E_mol
          TotEng Press
10000 0 -1080.3783 8491.0025
7410.6242 4260.3719

The last term pressure seems to be very high. I am working in real
units, so pressure is 4260 atmospheres. Does it looks feasible. I
expect the value of pressure be close to 1.

I also used the compute command, and the values are close to this one.


Pressures can be big and fluctuate a lot, esp if your
system is small.


Hi Steve

I want to run a NPT calculation at 300K and 1 atm. When using fix
npt, for the pressure start and stop what values should I specify. I
worked with 0 &1 and also 1 & 1 but in the thermo output I see "nan"
instead of a number.


Nans would be b/c your system blew up. Specify
1 atm for the start and stop pressure. If it blows
up you have other problems.