3d States Research Articles

Atomically Dispersed Iridium on Polyimide Support for Acidic Oxygen Evolution.

Designing a high-performing iridium (Ir) single-atom catalyst is desired for acidic water electrolysis, which shows enormous potential given its high catalytic activity toward acidic oxygen evolution reaction (OER) with minimum usage of precious Ir metal. However, it still remains a substantial challenge to stabilize the Ir single atoms during the OER operation without sacrificing the activity. Here, we report a high-performing OER catalyst by immobilizing Ir single atoms on a polyimide support, which exhibits a high mass activity on a carbon paper electrode while simultaneously achieving outstanding stability with negligible decay for 360 h. The resulting electrode (denoted as Ir1-PI@CP) reaches a 49.7-fold improvement in mass activity compared to the counterpart electrode prepared without polyimide support. Both our experimental and theoretical results suggest that, owing to the strong metal-support interactions, the polyimide support can enhance the Ir 5d states of Ir single atoms in Ir1-PI@CP, which can tailor the adsorption energies of intermediates and decrease the thermodynamic barrier at the rate-determining step of the OER, but also facilitate the proton-electron-transfer process and improve the reaction kinetics. This work offers an alternative avenue for developing single-atom catalysts with superior activity and durability toward various catalytic systems and beyond.

Material Parameter Identification for a Stress-State-Dependent Ductile Damage and Failure Model Applied to Clinch Joining

Similar to bulk metal forming, clinch joining is characterised by large plastic deformations and a variety of different 3D stress states, including severe compression. However, inherent to plastic forming is the nucleation and growth of defects, whose detrimental effects on the material behaviour can be described by continuum damage models and eventually lead to material failure. As the damage evolution strongly depends on the stress state, a stress-state-dependent model is utilised to correctly track the accumulation. To formulate and parameterise this model, besides classical experiments, so-called modified punch tests are also integrated herein to enhance the calibration of the failure model by capturing a larger range of stress states and metal-forming-specific loading conditions. Moreover, when highly ductile materials are considered, such as the dual-phase steel HCT590X and the aluminium alloy EN AW-6014 T4 investigated here, strong necking and localisation might occur prior to fracture. This can alter the stress state and affect the actual strain at failure. This influence is captured by coupling plasticity and damage to incorporate the damage-induced softening effect. Its relative importance is shown by conducting inverse parameter identifications to determine damage and failure parameters for both mentioned ductile metals based on up to 12 different experiments.

Non-trivial evolution of the Dirac cone in chromium doped Dirac semimetal Cd3As2

The magnetic doping of Dirac semimetals breaks their time-reversal symmetry thus giving rise to anomalous transport phenomena promising for applications. While the Dirac cone (DC) manifestations were observed in the electron transport of (Cd1−xCrx)3As2 alloys up to x = 0.06, their mechanism remains challenging. To address this challenge, we performed DFT calculations of the (Cd0.96Cr0.04)3As2 alloy with the non-magnetic (NM), ferromagnetic (FM), and antiferromagnetic (AFM) spin orders. It was found that the NM state is unstable, while the FM state has the lowest energy. The band structure analysis revealed that Cr 3d states are distributed in energy not uniformly, but with Cr-free windows, in which the Dirac spectrum can survive. The only exception is the Dirac point vicinity, where a narrow gap is formed. Outside the window, the DC band strongly hybridizes with the Cr 3d states and disappears. Near EF, such a Cr-free window with the DC band exists only in the FM↓ state and is absent in the NM, FM↑, and AFM states. The Fermi surface of FM (Cd1−xCrx)3As2 has two parts: the DC↓ sheet with the velocity vF ≈ 1∙106 m/s and several sheets with low vF, originating from Cr 3d↑ states. As an example of transport properties, the dc conductivity of FM (Cd1−xCrx)3As2 was estimated. We found that at T→0 K the DC↓ electrons have a very large transport lifetime and therefore dominate in the conductivity. In this dominance, the role of the Cr-free window is double: it ensures the DC↓ surviving and greatly reduces an admixture of Cr 3d↓ orbitals to DC↓ states, so suppressing the scattering of DC↓ electrons by doped Cr atoms. This mechanism looks rather general and may be applied to the design of magnetic topological alloys.

Geometrical, elastic, electronic, phonon, and optical properties of Na3AgO2 from first-principles calculation

In this paper, the geometrical, elastic, electronic, phonon, and optical properties of Na3AgO2 have been systematically studied by first-principles calculation. The results show that Na3AgO2 is mechanically stable and has small compressibility. Na3AgO2 is an indirect band-gap semiconductor with weak interatomic interaction. The bandgap calculated by HSE06 is 2.314 eV, and that calculated by GGA is 1.261 eV. For Na3AgO2, in the valence band near the Fermi level, the curve peaks of TDOS at −2.11 eV and −0.885 eV are primarily composed of O 2p states, which hybridize the 4 d and 4p states of Ag. The conduction band mainly consists of the 4p, 4 d, and 5s states of Ag, while hybridizing a few 2p states of O and a few 2p and 3s states of Na. As can be seen from the phonon dispersion spectrum there is no negative phonon frequency in the whole Brillouin region, indicating the structure is stable. Mulliken bond population of Na3AgO2 shows that O–Ag bonds have strong covalency, O–Na bonds have strong ionic properties, Na–Na bonds and Na–Ag bonds are antibonding. Na3AgO2 has a small reflectivity and a small absorption coefficient in the direction of (100) and (010) and has good transparency. The transparency of blue-violet light in the (001) direction is not as good as that of low-energy visible light. The obtained results lead to the conclusion that Na3AgO2 is a promising p-type transparent conducting material and is expected to be applied in practice.

In search of coloured alloys resembling gold: Structure and optical properties of LiCu2Ga1−xAlx and Li(Cu1–yNiy)2Ga

The Li-containing solid solutions LiCu2Ga1–xAlx and Li(Cu1–yNiy)2Ga were prepared by induction heating. LiCu2Ga1–xAlx retains the Cu2MnAl-type (full Heusler) structure of LiCu2Ga for x = 0–0.7 and then adopts the CsCl-type structure for x = 0.9–1.0. The solid solution Li(Cu1–yNiy)2Ga forms for y = 0–0.5 with the Cu2MnAl-type structure. Solid-state 7Li NMR spectra for LiCu2Ga1–xAlx suggest that Li atoms occupy unique sites, but there is some uncertainty about the intermediate members of this solid solution. These compounds show high reflectivity in the yellow region and an absorption edge caused by interband transitions from filled Cu 3d states to empty bands. The yellow colour of LiCu2Ga gradually changes to red as Ga is substituted by Al because the absorption edge shifts to lower energy, and it becomes lighter yellow as Cu is substituted by Ni because the relative reflectivity decreases. For low levels of substitution by Al (x = 0.1) or Ni (y = 0.1), the chromaticity coordinates are close to those of elemental gold.

Influence of nitrogen stoichiometry and the role of Sm 5d states in SmN thin films

We report a comprehensive study of the synthesis of epitaxial SmN thin films on LaAlO3 (100) by molecular beam epitaxy under slow-growth conditions. By carefully tuning the substrate temperature and the molecular nitrogen partial pressure, we are able to control the nitrogen content of our samples and produce near-stoichiometric, well-ordered SmN thin films. The influence of nitrogen defects on the samarium ion valence and the electronic structure is investigated by x-ray absorption and photoelectron spectroscopy, suggesting that the empty Sm 5d states may act as a charge reservoir stabilizing the 4f5 configuration in the nitrogen-deficient compound. The spectra also reveal a significant hybridization of the Sm 4f and N 2p states. Published by the American Physical Society 2024

Numerical investigation of the bearing performance of Thin- and Thick-Ply hybrid laminates

This publication presents a numerical investigation of Thin-Ply Hybrid CFRP bolted joints. In addition to Thin- and Thick-Ply specimens, hybrid specimens are investigated by substituting a part of the 90° CFRP layers with stainless steel foils. The numerical investigations are based on preliminary experimental work, which showed that fibre kinking led to final failure. A modelling strategy that includes 3D stress states and fibre kinking is chosen. The influence of micro-damages such as matrix cracks decreases with decreasing layer thickness. Therefore, and to avoid high computational power, primarily micro-damages such as matrix cracks are not included. The results of the simulations of the Thin-Ply and the hybrid samples show a good agreement with the experimental results. By hybridisation, the bearing performance can be significantly increased. It is shown that the modelling approach of not including micro-damage is well applicable for thinner plies but reaches its limits for thicker plies.

Spectroscopic evidence of spin-state excitation in d-electron correlated semiconductor FeSb2

Iron antimonide (FeSb2) has been investigated for decades due to its puzzling electronic properties. It undergoes the temperature-controlled transition from an insulator to an ill-defined metal, with a cross-over from diamagnetism to paramagnetism. Extensive efforts have been made to uncover the underlying mechanism, but a consensus has yet to be reached. While macroscopic transport and magnetic measurements can be explained by different theoretical proposals, the essential spectroscopic evidence required to distinguish the physical origin is missing. In this paper, through the use of X-ray absorption spectroscopy and atomic multiplet simulations, we have observed the mixed spin states of 3d 6 configuration in FeSb2. Furthermore, we reveal that the enhancement of the conductivity, whether induced by temperature or doping, is characterized by populating the high-spin state from the low-spin state. Our work constitutes vital spectroscopic evidence that the electrical/magnetical transition in FeSb2 is directly associated with the spin-state excitation.

Hydrogen Adsorption on Ordered and Disordered Pt-Fe and Pt-Co Alloys.

The bulk properties and surface chemical reactivity of compositionally disordered Pt-Fe and Pt-Co alloys in the fcc A1 phase have been investigated theoretically in comparison to the ordered alloys of the same compositions. The results are analyzed together with our previously reported findings for Pt-Ni. Nonlinear variation is observed in lattice constant, d band center, magnetic moment, and hydrogen adsorption energy across the composition range (0-100 atomic % of Pt, x Pt). The Pt 5d states are strongly perturbed by the 3d states of the base metals, leading to notable density of states above the Fermi level and residual magnetic moments at high x Pt. Surface reactivity in terms of average H adsorption energy varies continuously with composition between the monometallic Fe-Pt and Co-Pt limits, going through a maximum around x Pt = 0.5-0.75. Close inspection reveals a significant variation in site reactivity at x Pt < 0.75, particularly with disordered Pt-Fe alloys due in part to the inherent disparity in chemical reactivity between Fe and Pt. Furthermore, the strong interaction between Fe and Pt causes Pt-rich sites to be less reactive toward H than Pt-rich sites on disordered Pt-Ni alloy surfaces, despite less compressive strain caused. These results provide theoretical underpinnings for conceptualizing and understanding the performance of these Pt-base metal alloys in key catalytic applications and for efforts to tailor Pt-alloys as catalysts.

Theoretical Study of Catalytic Performance of Pristine M2C and Oxygen-Functionalized M2CO2 MXenes as Cathodes for Li-N2 Batteries.

Li-N2 batteries are a promising platform for electrochemical energy storage, but their performance is limited by the low activity of the cathode catalysts. In this work, density functional theory was used to study the catalytic activity of the pristine M2C and oxygen-functionalized M2CO2 MXenes (M = Sc, Ti, and V) as cathodes for Li-N2 batteries. The calculated results suggest that the pristine M2C MXenes (M = Sc, Ti, and V) show high electrical conductivity due to the Fermi level crossing the metal 3d states. The stable adsorption of N2 occurs on M2C MXenes via a side-on model and strengthens gradually with decreasing metal atomic number. Furthermore, the kinetics of N2 dissociation can be significantly accelerated by the coadsorption of Li on M2C MXenes. However, adsorption and dissociation of N2 on the M2CO2 surfaces are too difficult to occur due to strong electrostatic repulsion. The Li-mediated nitrogen reduction reaction during discharge proceeds favorably via (N + N)* → (LiN + N)* → (LiN + LiN)* → (Li2N + LiN)* → (Li2N + Li2N)* → (Li3N + Li2N)* → (Li3N + Li3N)* to form two isolated Li3N* on M2C MXenes. The calculated charge-discharge overpotentials decrease in the order of Sc2C < Ti2C < V2C. Notably, the Sc2C MXene has great potential as a cathode catalyst for Li-N2 batteries because of its high electrical conductivity, strong N2 adsorption, favorable Li-mediated N2 dissociation, and ultralow discharging, charging, and total overpotentials (0.07, 0.06, and 0.13 V). This study offers a theoretical foundation for future research on Li-N2 batteries.

Impact of Au on the transition temperature and photocatalytic activity of TiO2

The effect of gold (Au) addition on the anatase to rutile transition temperature (ART) of titanium dioxide (TiO2) was investigated. Concentrations of 2, 4, 8 and 16 mol. % of Au have been synthesised via a sol–gel technique and calcined at various temperatures (500–900 °C). The inclusion of gold improves the ART at 700 °C, maintaining 44.5 % anatase content for 4 % Au. Density functional theory studies indicated that the addition of Au in the anatase phase results in considerable lattice distortions, while Au 4d states and occupied Ti 3d orbitals contribute to the valence-conduction band energy gap upon doping. However, no sign of lattice substitution was observed in the experimental analysis. Instead, we demonstrate that the actual structure is well described by gold nanoparticles deposited on anatase and present a detailed DFT description of gold-modified anatase (101). All Au-TiO2samples exhibit reduced photocatalytic degradation properties compared to the control TiO2 at 500 °C. However, after calcining at 600 °C the addition of Au increases the photocatalytic activity of TiO2 from 49 % to 61 %, at an optimal concentration of 2 % Au-TiO2. The modification of titania with gold does push the transition temperature higher. However, this comes at the cost of reduced activity for 1,4-dioxane degradation, with the unmodified titania sample having better overall photocatalytic activity.

Ce[formula omitted] ion-induced distortion in a perovskite-structured KMgF3 single crystal

We investigate the local structural distortion induced by ▪ ion in a (cubic) perovskite-structured KMgF3 crystal for potential vacuum ultraviolet (VUV) applications. The crystal with 1.0 mol% nominal doping concentration exhibits five absorption bands centered at 196, 203, 209, 227, and 233 nm and two emission bands centered at 266 and 282 nm. These absorption and emission bands are attributed to the 4f−5d transitions of the ▪ ion. Our Ce K- and ▪-edge XAS analyses confirm the presence of ▪ oxidation state in the KMgF3 crystal. Our analyses reveal a significantly distorted coordination environment which has a coordination number (CN) of 5.03±0.55 and an average Ce–F bond length of 2.44±0.01 Å. Strong mixing of the 4f and 5d states and large ligand-field effects are also implied in the Ce ▪-edge XANES spectrum, as evidenced by an intense pre-edge peak. Optically, these mixing and ligand field effects conform to the large crystal field splitting of 1.03 eV (8285 ▪ ). Although this was the case, ▪ -doped KMgF3 remains a candidate VUV optical material due to its small Stokes shift of 0.64eV (5141 ▪ ).

Mesoscale Model for Composite Laminates: Verification and Validation on Scaled Un-Notched Laminates.

This paper presents a mesoscale damage model for composite materials and its validation at the coupon level by predicting scaling effects in un-notched carbon-fiber reinforced polymer (CFRP) laminates. The proposed material model presents a revised longitudinal damage law that accounts for the effect of complex 3D stress states in the prediction of onset and broadening of longitudinal compressive failure mechanisms. To predict transverse failure mechanisms of unidirectional CFRPs, this model was then combined with a 3D frictional smeared crack model. The complete mesoscale damage model was implemented in ABAQUS®/Explicit. Intralaminar damage onset and propagation were predicted using solid elements, and in-situ properties were included using different material cards according to the position and effective thickness of the plies. Delamination was captured using cohesive elements. To validate the implemented damage model, the analysis of size effects in quasi-isotropic un-notched coupons under tensile and compressive loading was compared with the test data available in the literature. Two types of scaling were addressed: sublaminate-level scaling, obtained by the repetition of the sublaminate stacking sequence, and ply-level scaling, realized by changing the effective thickness of each ply block. Validation was successfully completed as the obtained results were in agreement with the experimental findings, having an acceptable deviation from the mean experimental values.

Coexistence of Ferromagnetism and Superconductivity at KTaO3 Heterointerfaces.

The coexistence of superconductivity and ferromagnetism is a long-standing issue in superconductivity due to the antagonistic nature of these two ordered states. Experimentally identifying and characterizing novel heterointerface superconductors that coexist with magnetism presents significant challenges. Here, we report the observation of two-dimensional long-range ferromagnetic order in a KTaO3 heterointerface superconductor, showing the coexistence of superconductivity and ferromagnetism. Remarkably, our direct current superconducting quantum interference device measurements reveal an in-plane magnetization hysteresis loop persisting above room temperature. Moreover, first-principles calculations and X-ray magnetic circular dichroism measurements provide decisive insights into the origin of the observed robust ferromagnetism, attributing it to oxygen vacancies that localize electrons in nearby Ta 5d states. Our findings suggest KTaO3 heterointerfaces as time-reversal symmetry breaking superconductors, injecting fresh momentum into the exploration of the intricate interplay between superconductivity and magnetism enhanced by the strong spin-orbit coupling inherent to the heavy Ta in 5d orbitals.

Ultrastrong magnon-magnon coupling and chiral spin-texture control in a dipolar 3D multilayered artificial spin-vortex ice

Strongly-interacting nanomagnetic arrays are ideal systems for exploring reconfigurable magnonics. They provide huge microstate spaces and integrated solutions for storage and neuromorphic computing alongside GHz functionality. These systems may be broadly assessed by their range of reliably accessible states and the strength of magnon coupling phenomena and nonlinearities. Increasingly, nanomagnetic systems are expanding into three-dimensional architectures. This has enhanced the range of available magnetic microstates and functional behaviours, but engineering control over 3D states and dynamics remains challenging. Here, we introduce a 3D magnonic metamaterial composed from multilayered artificial spin ice nanoarrays. Comprising two magnetic layers separated by a non-magnetic spacer, each nanoisland may assume four macrospin or vortex states per magnetic layer. This creates a system with a rich 16N microstate space and intense static and dynamic dipolar magnetic coupling. The system exhibits a broad range of emergent phenomena driven by the strong inter-layer dipolar interaction, including ultrastrong magnon-magnon coupling with normalised coupling rates of Δfν=0.57\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{\\Delta f}{\ u }=0.57$$\\end{document}, GHz mode shifts in zero applied field and chirality-control of magnetic vortex microstates with corresponding magnonic spectra.

Energy structure of mixed halide CeF2Cl and CeFCl2 crystals

The band energy structures of CeF2Cl and CeFCl2 crystals have been calculated using the projector augmented-wave (PAW) method and the hybrid exchange-correlation functional PBE0. The valence band top consists of 2p states of F and 3p states of Cl. An energy gap is observed between the 5d states of Ce in the bottom part of the conduction band of both crystals, forming two subbands, 5d1 and 5d2, with very different effective electron masses (2.49 m0 and 0.19 m0 for CeF2Cl and 5.95 m0 and 0.84 m0 for CeFCl2, respectively). The 4f states of Ce are placed within the forbidden band. The obtained values for the band gap of CeF2Cl and CeFCl2 crystals are 6 eV and 4.6 eV, respectively.

Highly active ZnO/Fe3+-TiO2 photocatalysts for visible-light photodegradation application and its colour change behaviour by d-d transition

Highly active novel ZnO/Fe-TiO2 composite catalysts with p-n junction heterostructure have been fabricated by adding commercial ZnO and sol–gel derived Fe-TiO2 nano-powders controlled by grinding and drying. This work reported that doped Fe (III) with TiO2 form a p-type semiconductor and whereas ZnO is an n-type semiconductor. The slight variation of electronegativity between ZnO and TiO2 causes a strong rectifying action for the formation of an interface between ZnO and Fe-TiO2. The occurrence of red shift phenomenon in absorption spectrum of the samples suggest the outcome of d-d transition of Fe3+ (2T2g → 2A2g, 2T1g) and the charge transfer transition between interacting Fe3+ ions (Fe3+ + Fe3+ → Fe4+ + Fe2+). These Fe3+ 3d states in addition to oxygen vacancies and Ti3+ centers create band states, thereby favouring the electronic transition to these levels and resulting in narrowing of TiO2 band gap. A direct confirmation is the increase of Urbach energy with the lowering in the band gap of ZnO/Fe-TiO2.The crystal field splitting of d orbitals (5 degenerate orbitals) of Fe3+ and the approach of free ligand ions which split into two sets and Fe3+ ligand field transition is discussed schematically. The photocatalytic activities of these heterostructure photocatalysts were evaluated by degrading toxic cationic organic dyes such as Methylene Blue (MB) and Malachite Green Oxalate (MG) under visible light. The mechanism of photocatalysis has been recommended which is based on the relative band structure of the semiconductor and integrated heterostructure. The formation of a spike barrier in the CB at the interface gives rise to trap sites that capture the migration of charge carriers and occurs recombination of electron-hole pair at higher Fe(III) doping concentration. The dark adsorption property of the catalysts sample has been also studied.

QuadWire: An extended one dimensional model for efficient mechanical simulations of bead-based additive manufacturing processes

This paper presents the basis of a new mechanical model named QuadWire dedicated to efficient simulations of bead-based additive manufacturing processes in which elongated beads undergoing significant cooling and eigenstrain are assembled to form 3D parts. The key contribution is to use a multi-particular approach containing 4 particles per material point to develop an extended 1D model capable of capturing complex 3D mechanical states, while significantly reducing computation time with respect to conventional approaches. Indeed, 3D models usually require at least 3 to 4 elements across the bead section, which results in fine discretization along the tangential direction to avoid conditioning issues, and therefore very fine mesh of the entire 3D part. In the QuadWire model, the bead height and thickness are internal dimensions, enabling a significantly coarser mesh along the tangential direction. Thus, although the QuadWire has 12 degrees of freedom per material point instead of 3 for classical models, the total number of degrees of freedom is reduced by several orders of magnitude for large parts. The proposed model is classically developed within the framework of the principle of virtual power and standard generalized hyperelastic media (i.e., finite strain theory), which necessitates a thermodynamic analysis. Furthermore, the proposed approach includes native and manageable kinematic constraints between successive beads so that the stress state properly evolves during fabrication. Finite element analysis is used for numerical implementation under infinitesimal strain assumption for the sake of simplicity, and the QuadWire stiffness parameters are optimized so that the mechanical response fit conventional 3D approaches. To validate and demonstrate the capabilities of the proposed strategy, the evolution of displacements and stresses in fused deposition modeling of polylactide is simulated.

Electronic structures of skyrmionic polycrystalline MnSi thin film studied by resonance photoemission and x-ray near edge spectroscopy

Magnetic nanometric skyrmions are small complex vortex-like topological defects, mainly found in non-centrosymmetric crystals such as MnSi. They have potential applications for future spintronic devices. In this article, the structural, electronic, and magnetic states of the Mn atoms in a polycrystalline MnSi thin film facing a c-sapphire substrate were studied using x-ray diffraction, x-ray photo-emission spectroscopy, resonance photoemission spectroscopy (RPES), and extended x-ray absorption fine structure (EXAFS). The valence band spectra indicate the metallic nature of the film. The RPES study reveals the presence of major itinerant Mn 3d states near EF and also the mixed Mn 3d and Si 3s–3p states from 5.3 to 11.3 eV. The EXAFS spectrum does not show the existence of oxygen vacancies in the system, and the obtained magnetic moment in the non-stoichiometric MnSi thin film is a combination of the partially itinerant and partially localized Mn 3d states.

Resonant photoemission studies on Fe-Ni alloys

This paper investigates the electronic structure of Fe1−xNix (x = 0.32, 0.36, 0.4, 0.5) alloys employing high resolution photoelectron spectroscopy using synchrotron radiation. The valence bands and the core levels have been recorded at various on-resonance and off-resonance photon energies of Fe and Ni. An anti-resonance dip observed in the valence bands taken at Fe 3p → 3d resonance lies closer to the Fermi level compared to that observed at Ni 3p → 3d resonance, indicating larger density of itinerant Fe 3d electrons. Whereas, Ni 3d states are comparatively less itinerant in these alloys. The hybridization effects increase with increase of Fe content in the alloy system. The intensity of Ni L3M4,5M4,5 Coster-Cronig Auger transition observed with 853 eV (Ni 2p → 3d resonance) photon energy, drops down drastically for the Invar alloy (Fe0.64Ni0.36) as compared to other Fe-Ni alloys due to the existence of Ni in more than one local chemical surroundings as expected for Invar alloy. The electron-electron interaction energy (Udd) of Ni 3d shell is found to decrease with the decrease of Ni concentration. The 3p and 3s core levels of Fe and Ni recorded at 707 eV (Fe 2p → 3d resonance) are overwhelmed by various intense resonant Auger features such as Fe L3M2,3M2,3, Fe L3M2,3M4,5 and Fe L3M1M4,5. The 1S state of Fe L3M2,3M2,3 is greatly enhanced in the Invar alloy as compared to other alloys. The microscopic compositional in-homogeneity present in Invar alloy plays a crucial role in the screening of holes in Ni sites but does not contribute in screening the holes in Fe sites.