[lammps-users] very fluctuative pressure with NPT (now keep increasing)

Thank you for your explanation,
Now, I increase the number of atoms (from 72 only to 4608) in cell. Instead of fluctuative,now temperature and pressure keep increasing, for pressure even exceed the target. Is it normal trend? what should I do to make them close to the targeted value.

best regards,

my input file:

units real
atom_style charge
boundary p p p
read_data data.alfacristobalite
pair_style reax
pair_coeff * * ffield.reax 6 3

minimize 1.0e-4 1.0e-6 1000 1000
#velocity all scale 400

fix nptdistribution all npt 399 401 100 xyz 4999.0 5001.0 1000 drag 1.0

compute temperature all temp
compute coordinate all coord/atom 2.0
compute kineticenergy all ke
compute potentialenergy all pe
compute potentialperatom all pe/atom

thermo 10
thermo_style custom atoms step temp etotal pe ke ebond press
timestep 0.001

dump 1 all custom 1000 dumpSiOalfacristo*.dat id type xs ys zs q
run 50000

out.alfacristobalite (476 KB)

Your timestep is too small. You're not even
approaching the relaxation times you specified
in fix NPT for the T and P with your short run.