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.
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.
Ion trapping at the nanoscale within low-dimensional and bulk ice and their corresponding hydration properties are studied Using ab-initio technique. We study the structural and charge transfer properties of ion intercalated twodimensional(2D) and bulk ice and the corresponding ion hydration properties. We found that I) the nanochannel size and ionic radius are two important factors that control the spatial distribution of hydrated ions, ii) the alkali metal and halide ions are located in the center of the graphene-made nanochannel of size ≃ 6.5 Å, whereas in the nanochannel with size ≃ 9 Å, large (K+, Rb+, Cl−, Br−, and I−) and small (Li+, Na, and F−) ions are located in different positions, iii) the binding energy decreases with increasing the ionic radius, iv) the hydration of ions decreases for large ionswithin 2D ice giving a reduction in coordination number and allowing dehydration of large ions, and v) charge transfer mechanism is found to be different for large and small ions.
In recent decades, most of the natural and semi-natural ecosystems around the world have experienced excessive environmental loads due to human unsustainable activities that threaten their health and sustainability. Accordingly, the idea of ecosystem health has been proposed to monitor simultaneously the structure, function as well as the services that an ecosystem provides. In this research, moderate resolution imaging spectroradiometer 8-day land surface temperature product was used to measure temperature and land cover changes of Lake Urmia Basin for three months of June, July and August in a time period of 2000-2018. Time series data analysis was carried out using linear regression, Fourier series and Mann-Kendall test. Moreover, Moran index was used to analyze changes of the spatial pattern of indicators. To show the influence of Lake Urmia ecosystem services on its overall health, Total Ecosystem Health model was established by introducing normalized difference vegetation index, lake temperature, Moran index and temperature of the basin as indicators of Vigor, Structure, Resilience and Ecosystem Services, respectively. Based on output of the model, 54, 41 and 4% of the regions have obtained weak, moderate and strong ecosystem health, respectively. The results showed that despite the moderating role of Lake Urmia as a temperature regulator for its surrounding areas especially within 10 km, the decline of ecosystem health status in 95% of regions has occurred during the years 2000-2018. Therefore, to benefit from the ecosystem regulating services, the sustainability of other components involved in the total ecosystem health should be also ensured.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.