  The intercalated water into nanopores exhibits anomalous properties such as
ultralow dielectric constant.~Multi-scale modeling and simulations are used to
investigate the dielectric properties of various crystalline two-dimensional
ices and bulk ices. Although, the structural properties of two-dimensional
(2D-) ices have been extensively studied, much less is known about their
electronic and optical properties. First, by using density functional theory
(DFT) and density functional perturbation theory (DFPT), we calculate the key
electronic, optical and dielectric properties of 2D-ices. Performing DFPT
calculations, both the ionic and electronic contributions of the dielectric
constant are computed. The in-plane electronic dielectric constant is found to
be larger than the out-of-plane dielectric constant for all the studied
2D-ices. The in-plane dielectric constant of the electronic response is found
to be isotropic for all the studied ices. Secondly, we determined the dipolar
dielectric constant of 2D-ices using molecular dynamics simulations (MDS) at
finite temperature. The total out-of-plane dielectric constant is found to be
larger than 2 for all the studied 2D-ices. Within the framework of the
random-phase approximation (RPA), the absorption energy ranges for 2D-ices are
found to be in the ultraviolet spectra. For the comparison purposes, we also
elucidate the electronic, dielectric and optical properties of four crystalline
ices (ice VIII, ice XI, ice Ic and ice Ih) and bulk water.
