Effective low energy Hamiltonians and unconventional Landau level spectrum of monolayer C3_3N

We derive a low-energy effective $\mathbf{k}\cdot\mathbf{p}$ Hamiltonians for monolayer C$_{3}$N at the $\Gamma$ and $M$ points of the Brillouin zone where the band edge in the conduction and valence band can be found. Our analysis of the electronic band symmetries helps to better understand several results of recent ab-initio calculations[1,2] for the optical properties of this material. We also calculate the Landau level spectrum. We find that the Landau level spectrum in the degenerate conduction bands at the $\Gamma$ point acquires properties that are reminiscent of the corresponding results in bilayer graphene, but there are important differences as well. Moreover, because of the heavy effective mass, $n$-doped samples may host interesting electron-electron interaction effects.Comment: 10 pages, 5 figure

Surface Effect on Electronic, Magnetic and Optical Properties of PtCoBi Half-Heusler: A DFT Study

The electronic, magnetic, and optical properties of PtCoBi half-Heusler compound [001] surfaces and its bulk state have been investigated in the framework of density functional theory using GGA approximation. The half-metallic behaviors of CoBiterm, CoPt-term and PtBi-term decrease with respect to its bulk state. The spin polarization at the Fermi level is 73.2% for the bulk state, and it is -64.4% and -64.1% for the CoBi-term and PtBi-term, respectively while less polarization has been observed for the CoPt-term. All terminations have given almost similar optical responses to light. Plasmon oscillations for the terminations occur in the range of 12.5 to 14.5 eV (21 to 22 eV) along xx (zz), and it occurs at 23 eV for the bulk state. The refractive index for the bulk and all three terminations is very high in the infrared and visible areas, meaning a very strong metallic trend in these compounds. The phenomenon of super-luminance occurs for the incident light with energy exceeding 5.5 eV for all three terminations, and it occurs in the range of 10 eV for the bulk mode. These terminations show transparent behavior after the energy of 10 eV

Ab-initio study of mechanical, half-metallic and optical properties of Mn2ZrX (X = Ge, Si) compounds

The structural, elastic, electronic, magnetic and optical properties of Mn2 based full-Heusler alloys, Mn2ZrGe and Mn2ZrSi, were investigated by the first-principles full-potential linearized augmented plane wave (FP-LAPW) method in the framework of the Density Functional Theory. The AlCu2Mn-type structure was considered for both compounds. Based on E-V calculation, the ferromagnetic (FM) state was more stable than paramagnetic (PM) state. So, in the FM state the equilibrium lattice parameter was calculated as 5.995 Å and 6.079 Å for Mn2ZrSi and Mn2ZrGe respectively. The integer value 2.000 µB is obtained for total magnetic moments of both compounds that is perfectly consistent with Slater-Pauling rule. These alloys in the minority spin channel have metallic property while in the majority spin channel, they have band gap that confirms their semiconductor properties. Elastic properties of the alloys such as bulk modulus B, shear modulus G, Young’s modulus E and Poisson's modulus ν were obtained. Also, optical properties like dielectric function, reflectivity, energy loss function, absorption coefficient and optical conductivity were calculated. Keywords: Mn2ZrGe, Mn2ZrSi, DFT, Half-metal, Minority-majority spi

Synthesis of multiwalled carbon nanotubes on Cu-Fe nano-catalyst substrate

Considering the importance of metal nano catalysts, this research tries to apply sputtered nanoparticles as catalyst for growing carbon nanotubes and studies the effect of metals in modifying the catalytic property. One and bilayer Cu and Fe thin films were placed inside a quartz tube reactor to synthesis carbon nanotubes using acetylene gas as carbon source and argon gas for cooling down the reactor from 850 °C to room temperature. By scanning electron microscope images distribution of diameter of multi walled carbon nanotubes has recorded. The amounts of ID/IG obtained from Raman spectroscopy analysis showed the best quality of carbon nanotubes for Cu-Fe bilayer. Both analyses indicate the improve of catalytic effect of one transition metal by another one. On the other hand, multi walled carbon nanotubes are confirmed by both Raman spectroscopy and transmission electron microscopy images. Keywords: Transition metal nano catalyst, TCVD, MWCNT, Raman spectroscop

The electronic and optical properties of MgO mono-layer: Based on GGA-mBJ

The electronic and optical properties of MgO mono-layer were calculated based on the density functional theory (DFT) with FP-LAPW method using PBE-GGA and GGA-mBJ approximations. The electronic calculations of MgO mono-layer show a more interesting behavior than its bulk phase such as decreasing the band gap from 7.8 eV to 3.1 eV (for GGA) and 4.2 eV (for GGA-mBJ). Also, the MgO mono-layer has a direct band gap at Γ point in the Brillion Zone, and the effective masses of electrons are very greater than the effective mass of holes in this point. The optical coefficients such as dielectric parameters, energy loss functions, Refractions, Extinction and Absorption of this graphene-like (G-L) were calculated by RPA method which indicates the semiconducting properties of this mono-layer at the in-plane and perpendicular directions to emitting light. Keywords: MgO mono-layer, GGA, mBJ, Optical properties, Electronic propertie

Microstructure and optical properties of cobalt–carbon nanocomposites prepared by RF-sputtering

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