[lammps-users] Problem with reaxff, npt, volume and lattice constant

Dear Sir,

I am simulating a molecular crystal by using reaxff to determine it’s structural phase transtition from 143K to 300K. However after I am well equilibrate by using nvt and nve, when I start with npt, the volume and lattice length has high fluctuation. Which part has the problem? Is hbcut and precision will affect the data?
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in.p (545 Bytes)

data1.paa (919 Bytes)

Fluctuations in pressure and hence volume are normal when
running NPT. Espcially if you have a small system. Also
especially if you start away from equilibrium. When you
run NVE or NVT are you sitting at a pressure that is close
to the target you pick for NPT? If not, you are out of
equilibrium.

Steve