Then use one of the several thermostats in LAMMPS.
See section 4.16 of the manual for a discussion.
Steve
Hey Vidhya,
Are you going to be able to run a simulation for 28 nanoseconds? That’s certainly not a trivial amount of computational time unless you plan on making the O-H bonds rigid so that you can choose a timestep well above the period of O-H vibrations (which is on the order of femtoseconds). If you are making them rigid, read up on the shake fix.
Tyler