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Joining of dissimilar metallic materials such as Inconel alloys and steel by vacuum brazing with copper (Cu) filler metal is highly desirable in a wide range of applications, for example, in construction of rotors for high-speed electrical motors. However, experiments have shown poor wettability of Cu on IN718 during vacuum brazing. In this work, molecular dynamics (MD) simulations are performed to study nanoscale interfacial phenomena that occur during brazing of IN600 and IN718 with steel using Cu. Hybrid potentials data is verified using density function theory (DFT) based energy calculation and melting point test models. The results show that IN600 coheres well with liquid Cu, whereas Niobium containing IN718 exhibits inhibited diffusion of atoms from the Inconel alloy into the liquid Cu. Additionally, the simulations show that liquid Cu atoms diffuse well into the precipitate (γ ′ ′ phase) in IN718 but barely diffuse into the parent γ phase. [Display omitted] • Molecular dynamics simulations of Copper's wettability on Inconel 718. • Niobium in Inconel restricts diffusion of alloying elements from the bulk. • Precipitates in Inconel impede spreading of copper on the interface. [ABSTRACT FROM AUTHOR]

Our Compton profile measurements of Ti and TiH2 using readily available hard X-ray radiation at 27.5 keV, detected by both a Hitachi Vortex silicon-drift detector and a high-resolution superconducting transition-edge sensor array, are found to be in excellent accord with state-of-the-art density functional theory based calculations. The spherically averaged difference between the Compton profiles of TiH2 and Ti is well described by an inverted parabola, supporting an itinerant behavior of the electron gas screening the protons in the Ti matrix. Our experimental approach, validated by two different detectors, extends the applicability of Compton scattering technique to the readily accessible hard x-ray regime (below 30 keV). Our study suggests possibilities for experiments at low-flux bending magnet synchrotron beamlines and paves the way for the development of tabletop Compton experiments with x-ray tubes. [ABSTRACT FROM AUTHOR]

Recent discovery of superconductivity in the doped infinite-layer nickelates has renewed interest in understanding the nature of high-temperature superconductivity more generally. The low-energy electronic structure of the parent compound NdNiO2, the role of electronic correlations in driving superconductivity, and the possible relationship between the cuprates and the nickelates are still open questions. Here, by comparing LaNiO2 and NdNiO2 systematically within a parameter-free, all-electron first-principles density-functional theory framework, we reveal the role of Nd 4f electrons in shaping the ground state of pristine NdNiO2. Strong similarities are found between the electronic structures of LaNiO2 and NdNiO2, except for the effects of the 4f electrons. Hybridization between the Nd 4f and Ni 3d orbitals is shown to significantly modify the Fermi surfaces of various magnetic states. In contrast, the competition between the magnetically ordered phases depends mainly on the gaps in the Ni 3 d x 2 − y 2 band. Our estimated value of the on-site Hubbard U in the nickelates is similar to that in the cuprates, but the value of the Hund's coupling JH is found to be sensitive to the Nd magnetic moment. In contrast with the cuprates, NdNiO2 presents 3D magnetism with competing antiferromagnetic and (interlayer) ferromagnetic exchange, which may explain why the Tc is lower in the nickelates. The recent discovery of superconducting nickelates has reignited interest in these materials and whether they can shed light on the mechanism of unconventional superconductivity in the cuprates. Here, the authors use first principles calculations to investigate the f electrons and magnetic ordering effects in the infinite layer nickelates and elaborate on the role of the cuprate-like 3dx2-y2 band. [ABSTRACT FROM AUTHOR]