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Using density-functional calculations, we studied the interaction between interstitial impurities (N, C) and γ-Fe(111) surfaces doped, or not, with Cr, as well as the effect of Cr doping on the dissolution corrosion resistance of the γ-Fe(111) surface. The elementary processes studied afforded microscopic insights into the formation of a Cr-depleted zone, a phenomenon that leads to local corrosion of the stainless steel surface. The aim of this work was to study, at the atomic scale, the effects of N and C on the segregation behavior of Cr and the synergetic effect between co-doped atoms on the resistance to dissolution corrosion of austenitic stainless steel surfaces. The results showed that interstitial impurities prefer to be trapped at near-surface sites, which can impact the segregation behavior of Cr such that it shifts from the surface to the subsurface. Electrode potential calculations and density of states analysis demonstrated that doping with Cr or inserting interstitial impurities into the solid solution can improve the surface corrosion resistance of an fcc Fe substrate, but detrimental effects on the surface corrosion resistance are induced by interactions between Cr and interstitial impurity atoms in co-doped surfaces. The formation of near-surface Cr carbides and nitrides (speculated to be Cr2N and Cr23C6 due to the results obtained for particular co-doped surfaces) was also noted. The results of our theoretical calculations explain some of the experimental results observed at the atomic scale. [ABSTRACT FROM AUTHOR]

Effects of alloying elements in popular steels on the oxidation and dissolution corrosion of the surface of γ-Fe(111) have been investigated by performing density functional theory calculations within the local density approximation. First, the segregation of alloying atoms as well as preferential adsorption sites for oxygen and water were carefully examined, and it was found that all of the alloying elements considered had a tendency to segregate to the surface, and that the most preferred adsorption sites were the hexagonal closed packed (hcp) site and the top site for oxygen and water, respectively. The adsorption energies that characterized the tendency for oxygen or water to be adsorbed on the alloy surface showed that all ten alloying elements (especially Cr, Si, and Cu) were able to inhibit the adsorption of oxygen, and that all of the alloying elements except for Nb, Mo, and Ti inhibited water adsorption. The electrode potentials, which indicate the electrochemical stabilities of the surfaces of the alloys, suggested that all of these alloying elements (especially Cr, Mo, and Si) were able to suppress the adsorption of oxygen and water on the investigated surfaces, except for Nb and Ti in the case of water adsorption. Density of states analysis further indicated that all ten alloying elements (especially Cr, Si, Mo, and Cu) enhanced the corrosion resistance of the fcc Fe substrate, except for Nb and Ti with respect to dissolution corrosion. [ABSTRACT FROM AUTHOR]

To search for a high sensitivity sensor for cysteine, we investigated the adsorption of cysteine on intrinsic and Au-doped graphene sheets using density functional theory calculations. Binding energy is primarily determined by the type of atom which is closer to the adsorbed sheet. Compared with intrinsic graphene, Au-doped graphene system has higher binding energy value and shorter connecting distance, in which strong Au-S, Au-N and Au-O chemical bond interaction play the key role for stability. Furthermore, the density of states results show orbital hybridization between cysteine and Au-doped graphene sheet, but slight hybridization between the cysteine molecule and intrinsic graphene sheet. Large charge transfers exist in Au-doped graphene-cysteine system. The results of DOS and charge transfer calculations suppose that the electronic properties of graphene can be tuned by the adsorption site of cysteine. Therefore, graphene and Au-doped graphene system both possess sensing ability, except that Au-doped graphene is a better sensor for cysteine than intrinsic graphene. [ABSTRACT FROM AUTHOR]

By vertical sedimentation, silica micro-spheres were grown in different shapes of concave micro-zones which were etched on a (100) p-silicon substrate. The following were found: this method can effectively raise the quality of films by avoiding cracks; the geometry of the micro-zones affects the sediment of the film; regular hexagons and triangles best facilitate the growth of photonic crystals. This method is practical for its ability to fabricate self-assembly photonic crystals in previously designed small areas. [ABSTRACT FROM AUTHOR]

Abstract: Theoretical calculations via a transfer matrix method (TMM) were performed to investigate the possibility of fullerene/AlN multilayer films acting as one-dimensional (1D) photonic band gap (PBG) crystals. The response within and out of the periodic plane of (C60, C70)/AlN multilayers was studied. (C60, C70)/AlN multilayer films presented incomplete PBG behavior in UV region. C60/AlN multilayers with two pairs of 49nm-C60 and 21nm-AlN layers exhibited a high reflectivity of 90.4% at a wavelength of about 200nm. As a consequence, this photonic crystal may be important for achieving materials with an incomplete band gap in the UV region. [Copyright &y& Elsevier]

The structure, electronic and optical properties of 3C–SiC nano films were calculated according to first principles based on density functional theory. It is manifested that the nano films were structurally stable when the number of layers was increased to 12. Compared with bulk counterparts, nano films displayed narrower band gaps, and their Fermi energy levels were brought into the conduction band. The ε2(ω) of dielectric function, extinction coefficient, and absorption coefficient of the nano films were greater than that of the bulk in the ultraviolet range. With the layer numbers decreased, the values increased in the range. The results provide a guideline for 3C–SiC nano films to work for UV detectors. [ABSTRACT FROM AUTHOR]

First-principles calculations were performed to study the mechanical properties of typical precipitates of creep resistant magnesium alloys (Mg2Si, Mg2Ge, Mg2Sn and Mg3Zn3Y2). Formation enthalpies and cohesive energies, elastic constants C11, C12, C44, bulk modulus B0, Young's modulus E, shear modulus G, the ratios of shear modulus to bulk modulus G/B0, negative Cauchy pressure parameter (C12-C44) and Poisson's ratio n of four precipitates were discussed. The results show that Mg2Si and Mg2Ge are stiffer than Mg3Zn3Y2. The charge density was further investigated to clarify the electronic causes. [ABSTRACT FROM AUTHOR]

Structural, electronic and elastic properties for NiAl with 4d alloying elements M (Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd) have been studied using the first-principles pseudopotential density functional method within a generalized gradient approximation. From the elastic constants, C11, C12, C44, bulk modulus B0, Young's modulus E, the shear modulus G, the ratios of shear modulus to bulk modulus G/B0, negative Cauchy pressure parameter (C12 [?] C44) and Poisson's ratio n calculated after structural full relaxation, M (Tc, Ru, Rh, Pd) alloying addition in NiAl has been shown to increase the stiffness of NiAl and improve its ductility. The density of states and charge density contour involving alloying additions of Ru were further investigated to clarify the electronic causes of the alloying additions. [ABSTRACT FROM AUTHOR]

A new broadband filter, based on the high level bandgap in 1-D photonic crystals (PCs) of the form Si|air|Si|air|Si|air|Si|air|Si|air|Si is designed by the plane wave expansion method (PWEM) and the transfer matrix method (TMM) and fabricated by lithography. The optical response of this filter to normal-incident and oblique-incident light proves that utilizing the high-level bandgaps of PCs is an efficient method to lower the difficulties of fabricating PCs, increase the etching depth of semiconductor materials, and reduce the coupling loss at the interface between optical fibers and the PC device. [ABSTRACT FROM AUTHOR]

Abstract Solid‐state NMR analysis on wurtzite alloyed CdSe1−xSx crystalline nanoparticles and nanobelts provides evidence that the 113Cd NMR chemical shift is not affected by the varying sizes of nanoparticles, but is sensitive to the S/Se anion molar ratios. A linear correlation is observed between 113Cd NMR chemical shifts and the sulfur component for the alloyed CdSe1−xSx (0

Highlights: [•] Tensile process of Ni/Cr2O3 was investigated using first-principles method. [•] The softer Ni layers deform larger than the harder Cr2O3 layers. [•] Fracture occurs along the metal–oxide interface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Five Ni(111)/Cr2O3(0001) models were studied by using first-principles method. [•] O-terminated Cr2O3(0001) slabs is more active than Cr-terminated slabs. [•] Al atoms in Ni slab would diffuse into Cr2O3 slabs. [•] The Ni/Al2O3/Cr2O3 structure has better stability than that of Ni/Cr2O3. [Copyright &y& Elsevier]