The intercalated water into nanopores exhibits anomalous properties such as an ultralow dielectric constant. Multiscale 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 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 (ε el ) is found to be isotropic for all the studied ices. Second, we determined the dipolar dielectric constant of 2D ices using molecular dynamics simulations 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, the absorption energy ranges for 2D ices are found to be in the ultraviolet spectra. For 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.

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A multiscale modeling and simulation approach, including first-principles calculations, ab initio molecular dynamics simulations, and a tight binding approach, is employed to study band flattening of the electronic band structure of oxidized monolayer graphene. The width of flat bands can be tuned by strain, the external electric field, and the density of functional groups and their distribution. A transition to a conducting state is found for monolayer graphene with impurities when it is subjected to an electric field of ∼1.0 V/Å. Several parallel impurity-induced flat bands appear in the low-energy spectrum of monolayer graphene when the number of epoxy groups is changed. The width of the flat band decreases with an increase in tensile strain but is independent of the electric field strength. Here an alternative and easy route for obtaining band flattening in thermodynamically stable functionalized monolayer graphene is introduced. Our work discloses a new avenue for research on band flattening in monolayer graphene.

Because of their unusual fundamental behavior that arises at the molecular scale, the electrical conductivity of stacked graphene oxide (GO) sheets in the presence of external parameters is not adequately understood. Previous studies concentrated on the DC response of thin GO membranes giving their resistive switching properties. Here, we observe anomalous low-frequency (<1 Hz) oscillations in the electrical conductivity of micrometer size GO, which is repeated in a process over and over in an ongoing feedback loop. Such vibrations and their unique trajectories are not only fundamentally important but also have characteristic frequencies that can be directly linked to the formation and destruction of regions with sp2 hybridization. Also, the reported switching time (of the order of seconds) makes our resistive switching system different than all the previously reported systems and introduces a new class of switching phenomena. The observed phenomena improve our understanding of the electrical conductivity of GO membranes and the corresponding microscopic details that pave the way for the promising application of these new observed low-frequency oscillations.

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