ABSTRACT
Employing first-principles calculations based on density functional theory (DFT), we designed a novel two-dimensional (2D) elemental monolayer allotrope of carbon called hexatetra-carbon. In the hexatetra-carbon structure, each carbon atom bonds with its four neighboring atoms in a 2D double layer crystal structure, which is formed by a network of carbon hexagonal prisms. Based on our calculations, it is found that hexatetra-carbon exhibits a good structural stability as confirmed by its rather high calculated cohesive energy -6.86 eV/atom, and the absence of imaginary phonon modes in its phonon dispersion spectra. Moreover, compared with its hexagonal counterpart, i.e., graphene, which is a gapless material, our designed hexatetra-carbon is a semiconductor with an indirect band gap of 2.20 eV. Furthermore, with a deeper look at the hexatetra-carbon, one finds that this novel monolayer may be obtained from bilayer graphene under external mechanical strain conditions. As a semiconductor with a moderate band gap in the visible light range, once synthesized, hexatetra-carbon would show promising applications in new opto-electronics technologies.
ABSTRACT
In a recent paper, Molaei et al. (J Mol Model 27:181-188, 2021) studied the H[Formula: see text]S gas adsorption on transition metal (TM) doped phosphorene monolayer using the density functional theory. They claimed that Ti-, V-, Fe- and Sc-doped phosphorene systems are more favorable than the other doped systems. Their electronic calculations showed that they did not consider spin-polarized calculations for TM doped structures. Here, we present all spin-polarized electronic calculations based on generalized gradient approximation (GGA) and GGA plus Hubbard correction (GGA+U). Our results reveal that doped systems are magnetic and thus spin-polarized effect must be considered in these structures.
ABSTRACT
A fast response time (0.1 s) magnetic field sensor has been demonstrated utilizing a photonic crystal fiber with nano-size air holes infiltrated with polyethylene glycol based magnetic fluid. The effect of magnetic nanoparticles concentration in the fluid on the magneto-optical sensor performance and its dependence under varying magnetic-field loads was investigated in detail. In particular, the sensor response was analytically modelled with a Langevin function with a good fit (R[Formula: see text]0.996). A threshold sensing point as low as 20 gauss was recorded and a detection range of 0-350 gauss was demonstrated by means of optical transmission measurements. The experimental results were validated by theory using a waveguide light transmission model fed by finite-element method simulations of the principal guided modes in the infiltrated fiber sensor. The simple interrogation scheme, high sensitivity and quick response time makes the proposed hybrid fiber-optic magneto-fluidic probe a promising platform for novel biochemical sensing applications.
