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Highlights: Inducing a localized crystalline iron pyrophosphate in amorphous iron phosphate overlayer. Enhanced photoelectrochemical water oxidation activity with long-term durability. The heterogeneous hybrid structure overcoming the energy barrier in water oxidation. A rational regulation of the solar water splitting reaction pathway by adjusting the surface composition and phase structure of catalysts is a substantial approach to ameliorate the sluggish reaction kinetics and improve the energy conversion efficiency. In this study, we demonstrate a nanocrystalline iron pyrophosphate (Fe4(P2O7)3, FePy)-regulated hybrid overlayer with amorphous iron phosphate (FePO4, FePi) on the surface of metal oxide nanostructure with boosted photoelectrochemical (PEC) water oxidation. By manipulating the facile electrochemical surface treatment followed by the phosphating process, nanocrystalline FePy is localized in the FePi amorphous overlayer to form a heterogeneous hybrid structure. The FePy-regulated hybrid overlayer (FePy@FePi) results in significantly enhanced PEC performance with long-term durability. Compared with the homogeneous FePi amorphous overlayer, FePy@FePi can improve the charge transfer efficiency more significantly, from 60% of FePi to 79% of FePy@FePi. Our density-functional theory calculations reveal that the coexistence of FePi and FePy phases on the surface of metal oxide results in much better oxygen evolution reaction kinetics, where the FePi was found to have a typical down-hill reaction for the conversion from OH* to O2, while FePy has a low free energy for the formation of OH*. [ABSTRACT FROM AUTHOR]

Using the first-principles calculations, the change in magnetism and electronic structures during Cu nucleation in bcc Fe system was investigated. For modeling the Fe-rich bcc FeCu alloy, FexCu1-x (x≥0.75) were employed in the supercell system. Nonmagnetic Cu atoms were precipitated on the (100) plane of bcc Fe crystal, whereas the magnetized Cu atoms preferred to be precipitated on the (110) plane. Magnetization energies showed a linear decrease as the Cu concentration increased in bcc Fe. The magnetic moments of Fe atoms increased for larger concentration of Cu atoms. Electron density of states showed that the enhanced magnetic moment of Fe atoms resulted from the shift of minority spin states toward higher levels, which was associated with the bond formation between Cu and Fe atoms. [ABSTRACT FROM AUTHOR]

Using the density-functional-theory-based atomic modeling, the stable interface structure and the resultant magnetocrystalline anisotropy (MCA) of the Fe/MgO(001) for magnetic random access memory have been studied. The most stable surface structure of Fe/MgO(001) thin-film system was found to be either defect free or possessing oxygen vacancies in a c(\2 \times \1) periodicity. The formation of the oxygen vacancies in c(\2 \times \1) periodicity on MgO(001) surface reduced the MCA of Fe layer from 1.38 to 0.31 meV/atom. The reduced MCA is originated from the filling of the minority states of the Fe orbital below Fermi level. [ABSTRACT FROM PUBLISHER]

Using ab initio calculations, we investigated the changes of the magnetic moment and electronic structures of Fe adatoms on strained graphene sheets. By the uniaxial tensile strains in armchair and zig-zag directions on graphene sheets, the amounts of charge transfers from graphene 2pz orbital to Fe adatom 3d orbitals were linearly increased. The magnetic moments of Fe, however, show the tendency of linear decrements with the uniaxial tensile strains. The increased Fe magnetic moments by uniaxialy graphene compressions resulted from the shifting of spin-minority states of electrons while the decreased Fe magnetic moments were due to the reduction in the spin-majority states of 3dxy-orbitals of the Fe adatom. [ABSTRACT FROM AUTHOR]

Abstract: A molecular dynamics (MD) method was used to quantitatively investigate the surface characteristics during the early stages of thin-film deposition, focusing on the cases of Fe and Cu on a Cu(111) system. Specifically, flux calculations of the incoming atoms were performed by extensively measuring the trajectory near the artificially structured Fe or Cu step positioned on the Cu(111) surface. Differences in the surface morphologies of Fe and Cu deposition on the Cu(111) surface could be successfully explained in terms of surface diffusion after 2 ML deposition and impact cascade diffusion. [Copyright &y& Elsevier]