Wavevector dependent dielectric constant of the MCY water model

The wavevector-dependent dielectric constant for a MCY model of water is evaluated in a wide region of wavenumbers by Monte Carlo simulations using the reaction field geometry. It is shown that values for the longitudinal component of the dielectric constant, calculated within the exact site-site description, differ in a characteristic way from those obtained by the point dipole approximation which is usually used in computer experiment. The intramolecular shape of the dielectric constant and the Kirkwood factor is examined in the infinite wavevector limit.