Electronic, dielectric and optical properties of two dimensional and bulk ice: a multi-scale simulation study

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

Tight-Binding Studio: A Technical Software Package to Find the Parameters of Tight-Binding Hamiltonian

We present the Tight-Binding Studio (TBStudio) software package for calculating tight-binding Hamiltonian from a set of Bloch energy bands obtained from first principle theories such as density functional theory, Hartree-Fock calculations or Semi-empirical band structure theory. This will be helpful for scientists who are interested in studying the electronic properties of structures using Green's function theory in tight-binding approximation. TBStudio is a cross-platform application written in C++ with a graphical user interface design that is user-friendly and easy to work with. This software is powered by Linear Algebra Package C interface library for solving the eigenvalue problems and the standard high-performance OpenGL graphic library for real-time plotting. TBStudio and its examples together with the tutorials are available for download from tight-binding.com

The Pragmatic Instruction Effects on Persian EFL Learners’ Noticing and Learning Outcomes in Request Forms

This study investigates the request strategies used by Persian learners of English as a Foreign Language (EFL), aimed at exploring the pragmatic instruction effects on their noticing constrained by different types of treatment tasks. The subsequent effect of the learners’ noticing on their learning outcomes is taken into account as well. Thirty learners were divided into two instructional (treatment) conditions: a form-comparison condition and a form-search condition. Discourse completion tests were used to generate data related to the request strategies used by each group in pre- and posttests. The treatment data were examined regarding the extent to which the learners had noticed the appropriate manner of request realization in English and were further compared with the posttest. The findings revealed that during the treatment, the amount of learners’ noticing the target request forms in the form-comparison condition was greater than the form-search condition. Furthermore, learners’ higher awareness of the target request forms in the form-comparison condition could lead them to have a better performance in their posttest

The properties of electron transport through CNT/trans-PA/CNT system

Abstract Using a tight-binding model and a tranfer-matrix technique, we numerically investigate the effects of the coupling strength, and the length of the molecule on the electronic transmission through a CNT/(single) molecule/CNT system. With trans-polyacetylene (trans-PA) as the molecule sandwiched between two semi-infinite carbon nanotube(CNT), we rely on Landauer formalism as the basis for studying the conductance properties of this system. Our calculations show that the conductance is sensitive to the CNT/molecule coupling and that it exponentially decreases with the increase in the length of the molecule, as expected