Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userWork function of {alpha}-Fe_{2}O_{3} : a DFT calculation
84
0
0.0
(
0
)
Authors
Chunshan He
Ask ChatGPT about the research
No Arabic abstract
The work functions of (001) and (00 -1) surfaces of {alpha}-Fe_{2}O_{3} are investigated with density functional theory and symmetry slab model. These two surfaces are found to be almost nonpolarized and their work functions are 6.10 eV and 5.49 eV respectively.
rate research
Read More
Recently, materials exhibiting colossal dielectric constant ($CDC$) have attracted significant attention because of their high dielectric constant and potential applications in electronic devices, such as high dielectric capacitors, capacitor sensors, random access memories and so on.
Atmospheric pressure plasma (APP) generates highly reactive species that are useful for surface activations. We demonstrate a fast regeneration of iron oxides, that are popular catalysts in various industrial processes, using microwave-driven argon APP under ambient condition. The surface treatment of hematite powder by the APP with a small portion of hydrogen (0.5%) lowers the oxides reduction temperature. A near-infrared laser is used for localized heating to control the surface temperature. Controlled experiments without plasma confirm the catalytic effect of the plasma. Raman, XRD, SEM, and XPS analyses show that the plasma treatment changed the chemical state of the hematite to that of magnetite without sintering.
In the present work, we study the structures and molecular geometries of $CH_{4}$, $SO_{2}$ and $O_{2}$ adsorbed on $Cr_{2}O_{3}(0001)$. Using computational calculations based on the density functional theory (DFT), we analyze the most suitable sites to carry out the adsorption of each of the molecules mentioned, and the influence of each species on the adsorption and dissociation of the others. The results allow us to understand the activation of the $Cr_{2}O_{3}(0001)$ surface, which leads to the presence of $SO_{2}$ during the oxidation of $CH_{4}$, as was experimentally verified.
$Co$-doping of $Fe_{3}O_{4}$ magnetic nanoparticles is an effective way to tailor their magnetic properties. When considering the two extreme cases of the $Co_{x}Fe_{3-x}O_{4}$ series, i.e. the $x=0$ and $x=1$ values, one finds that the system evolves from a negative cubic-anisotropy energy constant, $K_{C}^{-}<0$, to a positive one, $K_{C}^{+}>0$. Thus, what happens for intermediate $x$-compositions? In this work we present a very simple phenomenological model for the anisotropy, under the textit{macrospin} approximation, in which the resultant anisotropy is just directly proportional to the amount of $Co$. First, we perform a detailed analysis on a rather ideal system in which the extreme values have the same magnitude (i.e. $|K_{C}^{-}|=|K_{C}^{+}|$) and then we focus on the real $Co_{x}Fe_{3-x}O_{4}$ system, for which $|K_{C}^{+}|sim 18|K_{C}^{-}|$. Remarkably, the approach reproduces rather well the experimental values of the heating performance of $Co_{x}Fe_{3-x}O_{4}$ nanoparticles, suggesting that our simple approach may in fact be a good representation of the real situation. This gives rise to an intriguing related possibility arises: a $Co$-doping composition should exist for which the effective anisotropy tends to zero, estimated here as 0.05.
A neutron scattering investigation of the magnetoelectric coupling in PbFe_{1/2}Nb_{1/2}O_{3} (PFN) has been undertaken. Ferroelectric order occurs below 400 K, as evidenced by the softening with temperature and subsequent recovery of the zone center transverse optic phonon mode energy (hbar Omega_{0}). Over the same temperature range, magnetic correlations become resolution limited on a terahertz energy scale. In contrast to the behavior of nonmagnetic disordered ferroelectrics (namely Pb(Mg,Zn)_{1/3}Nb_{2/3}O_{3}), we report the observation of a strong deviation from linearity in the temperature dependence of (hbar Omega_{0})^{2}. This deviation is compensated by a corresponding change in the energy scale of the magnetic excitations, as probed through the first moment of the inelastic response. The coupling between the short-range ferroelectric and antiferromagnetic correlations is consistent with calculations showing that the ferroelectricity is driven by the displacement of the body centered iron site, illustrating the multiferroic nature of magnetic lead based relaxors in the dynamical regime.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
