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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]

Abstract  Density functional theory (DFT) combined with the conductor-like solvent model (COSMO) can provide valuable atomistic level insights into CO adsorption on Cu surface interactions in liquid paraffin. The objective of this research was to investigate the solvent effect of liquid paraffin. It was found that both structural parameters and relative energies are very sensitive to the COSMO solvent model. Solvent effects can improve the stability of CO adsorption on Cu (110) and (100) surfaces and the extent of CO activation. [ABSTRACT FROM AUTHOR]