Is there a maximum time limit to run a MD simulation?

GROMACS version: 2019
GROMACS modification: No

I’m performing a NPT simulation with 150ns (0.001 time step) for ice structure.
Is there a time limit to run a MD calculation?
How Gromacs deals if there is a phase transition?

Thank you in advance,
Inna Nangoi

There is no time limit. It is all up to you how long you want to run a simulation. Simulation length is determined by nsteps option in mdp file or -nsteps argument of mdrun command. Gromacs simply does integration of Newton’s equation of motion, it is oblivious about any phase change.