[lammps-users] TIP4P and NPT

Dear all,

I am trying to compute the density of water. For a start I have just used a
very small box consisting of 703 molecules. Using the NPT, I find that the
box size increases dramatically ( nearly 200 times larger in each
dimension), then reduces and increases again. The simulation becomes
extremely slow. I started off with the correct box size for the density of
water at 1 atm pressure, so I would expect to recover approximately this box

Is there something wrong with my input ? I am using TIP4P to model the water
molecules. Attached are my input files


Huck Beng

in.swnt_c (1.04 KB)

data.swnt (215 KB)

You're trying to do it in metal units. Have you done
it successfully in real units? Ahmed has test files
for TIP3P water in real units he can send you.


Or probably you would like to increase the Pdamp to a large value.