The choice of the time step and cutoff


I want to simulate molecular system of water (5000 molecules), argon (5000
atoms) and butan (5000 molecules).
What is correct time step and cutoff radius for simulations of water, argon
and butan?
Can anyone send me some links to articles, books where i can read about
Maybe someone knows some methods of the choice of these parameters?

Please help me!!

I would find a paper using the model you
intend to use and see what they did. Failing
that, you can experiement and see what kind
of energy conservation you get with different
size timesteps.