  Currently, the study of systems confined within various materials, such as
graphene and graphene oxide, for diverse applications such as water
desalination, metal separation from water, battery cells, and high-efficiency
capacitors, is very common. Among these systems, water is a prominent subject
of investigation. Understanding the impact of the number of molecules and the
optimal cutoff radius is essential in order to determine the parameters. This
study investigates the dielectric properties of H2O in relation to both the
number of molecules and the cutoff radius within the simulation cell. We employ
the flexible water model FBA/$\epsilon$, known for its improved accuracy in
reproducing water properties across various thermodynamic states. We range from
60 to 1372 molecules and use cutoff radius from 6 nm to 1.2 nm, encompassing a
wide range of calculations to assess their impact on the simulation results,
including critical properties like the dielectric constant, density, and phase
change enthalpy.
