Unpaired Electron Research Articles

Computational discovery of two-dimensional rare-earth iodides: promising ferrovalley materials for valleytronics

Two-dimensional Ferrovalley materials with intrinsic valley polarization are rare but highly promising for valley-based nonvolatile random access memory and valley filter devices. These ferromagnetic materials exhibit valleys at or near the Fermi level with intrinsic magnetism. The strong coupling between magnetism and spin–orbit coupling induces intrinsic valley polarization. Using Kinetically Limited Minimization, an unconstrained crystal structure prediction algorithm, and prototype sampling based on first-principles calculations, we have discovered new Ferrovalley materials, rare-earth iodides RI2, where R is a rare-earth element belonging to Sc, Y, or La-Lu, and I is Iodine. The rare-earth iodides are layered and demonstrate either 2H, 1T, or 1T d phase as the ground state in bulk, analogous to transition metal dichalcogenides (TMDCs). The calculated exfoliation energy of monolayers (MLs) is comparable to that of graphene and TMDCs, suggesting possible experimental synthesis. The MLs in the 2H phase exhibit ferromagnetism due to unpaired electrons in d and f orbitals. Throughout the rare-earth series, d bands have valley polarization at K and points in the Brillouin zone in the vicinity of the Fermi level. Large intrinsic valley polarization in the range of 15–143 meV without external stimuli is observed in these Ferrovalley materials, which can be enhanced further by applying an in-plane bi-axial strain. These valleys can selectively be probed and manipulated for information storage and processing, potentially offering superior performance beyond conventional electronics and spintronics. We further show that the 2H ferromagnetic phase of RI2 MLs possesses non-zero Berry curvature and exhibits anomalous valley Hall effect with considerable anomalous Hall conductivity. Our work will incite exploratory synthesis of the predicted Ferrovalley materials and their application in valleytronics and beyond.

Photo-induced organic radical species in naphthalenediimide-based metal-organic framework for reversible photochromism and near-infrared photothermal conversion

Multifunctionality and adjustability of the stimulating responsive materials are the main reasons that make them so useful for practical application. In this paper, an inimitable crystalline metal-organic framework with both reversible photochromism and near-infrared photothermal conversion was successfully obtained by one-pot synthesis. Single-crystal structural analysis indicates that the naphthalenediimide(NDI)-based metal-organic framework is of significant lone pair-π interactions leading to the occurrence of effective electron delocalization in the photo-generation of charge-separation state for this crystalline material; simultaneously, the framework possesses hydrophobic cavities among the periodical NDI arrangements giving rise to effective structural separation. Consequently, the photo-generated colored radical anions can be recovered to corresponding light-colored neutral molecules in the existence of ozone or dark treatment, giving rise to reversible photochromic behavior for the crystalline framework. On the other hand, the unpaired electron can be delocalized across the π-system due to the existence of significant lone pair-π interactions in framework, in consequence of which irradiated sample undergoes a relatively small loss of organic radical anions after keeping in open air for at least 20 days. Atmospheric-stable organic radical anions with near-infrared absorption can be further used for photothermal conversion. This work provides in-depth insight into the correlation of charge-separation and the whole performance of materials and also extends the near-infrared photothermal conversion application of radical-doped crystalline materials.

Spin-State Regulation of Nickel Cobalt Spinel toward Enhancing the Electron Transfer Process of Oxygen Redox Reactions in Lithium–Oxygen Batteries

The development of a high-energy-density lithium–oxygen (Li–O2) battery is mainly determined by highly efficient electrocatalysts with excellent activity and stability, facilitating reversible oxygen redox reactions. Engineering the electron spin state provides a novel strategy to enhance the electrocatalytic activity of electrode materials. In this work, sulfur vacancy-enriched spinel NiCo2S4 (Vs-NiCo2S4) with high spin polarization is designed as an effective electrocatalyst for high-performance Li–O2 batteries. Subtle lattice distortion is induced by sulfur vacancy in spinel Vs-NiCo2S4, which strongly contributes to the formation of high spin states of Co3+ (HS, t2g4eg2) from the low spin states of Co3+ (LS, t2g6eg0) at active octahedral sites. The electron transitions of Co3+ from low to high spin enable the increase of the spin polarization and produce abundant unpaired electrons in the 3d orbital of Co3+, enhancing the adsorption of oxygen intermediates and boosting the electron transfer process of oxygen redox reactions. Density functional theory calculations indicate that the spin magnetic moment of Co3+ in Vs-NiCo2S4 is raised in comparison to that in NiCo2S4, which improves the catalytic activity of the material via lowering the energy barrier for electron transfer. Experimentally, Vs-NiCo2S4-based Li–O2 batteries exhibit a large specific capacity of 8707.0 mAh g–1 and long cycling life of 487 h. Furthermore, in situ differential electrochemical mass spectrometry results show that the ratio of electron to oxygen during oxygen redox reactions is close to 2, demonstrating the favorable formation and decomposition of Li2O2 on Vs-NiCo2S4 in a Li–O2 battery. This work presents a powerful strategy to rationally design efficient electrocatalysts via spin engineering to boost oxygen redox reaction kinetics in Li–O2 batteries.

Terminal Au-N and Au-O Units in Organometallic Frames.

Since gold is located well beyond the oxo wall, chemical species with terminal Au-N and Au-O units are extremely rare and limited to low coordination numbers. We report here that these unusual units can be trapped within a suitable organometallic frame. Thus, the terminal auronitrene and auroxyl derivatives [(CF3 )3 AuN]- and [(CF3 )3 AuO]- were identified as local minima by calculation. These open-shell, high-energy ions were experimentally detected by tandem mass spectrometry (MS2 ): They respectively arise by N2 or NO2 dissociation from the corresponding precursor species [(CF3 )3 Au(N3 )]- and [(CF3 )3 Au(ONO2 )]- in the gas phase. Together with the known fluoride derivative [(CF3 )3 AuF]- , they form an interesting series of isoleptic and alloelectronic complexes of the highly acidic organogold(iii) moiety (CF3 )3 Au with singly charged anions X- of the most electronegative elements (X=F, O, N). Ligand-field inversion in all these [(CF3 )3 AuX]- species results in the localization of unpaired electrons at the N and O atoms.

Qualitative and Quantitative Phytochemical Screening and Free Radical Scavenging Activity of Different Parts of Rubus ellipticus Sm.

Free radicals are molecules with reactive unpaired electrons which are produced during cell metabolism and create the oxidative stress inside tissue resulting in tissue damage. The aim of the present study was qualitative and quantitative phytochemical screening, determination of total phenolic and total flavonoid content, and free radical scavenging activity of different parts of ethnomedicinally used Rubus ellipticus Sm. plant. Root, stem, and leaves of Rubus ellipticus Sm. were collected from Annapurna Rural Municipality, Kaski, Western Nepal. Ethyl acetate and ethanol extracts of the plant parts were obtained by subsequent maceration process. The phytochemical screening of most of the extract showed the presence of phenols, carbohydrates, flavonoids, and glycosides. The ethanolic extract of stem showed the higher phenolic content with the value of 343.75 ± 2.21 µg GAE/mg. Ethanolic extract of stem had the highest amount of flavonoid content (1563.17 ± 10.79 µg QE/mg of extract), whereas all the ethyl acetate extracts of root, leaves and stem showed comparable flavonoid content. Ethanolic extracts of leaves showed potent DPPH free radical scavenging activity with IC50 value of 5.03µg/ml while ethyl acetate extract of stem showed the maximum free radical scavenging properties. The result depicted that the ethanolic extract of Rubus ellipticus Sm. showed the potent antioxidant activity by scavenging free radicals.

D 6 h Symmetric Radical Donor–Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

<i>D</i> ^{6 <i>h</i>} Symmetric Radical Donor–Acceptor Nanographene Modulated Interfacial Carrier Transfer for High-Performance Perovskite Solar Cells

The influence of ancillary NCS− ions on structural, spectroscopic, magnetic and biological properties of copper(II) l-argininato complex

The anions are one of the factors that govern the self-organization of the crystal structure involving [Cu(l−Arg)]2+ cation complex. Therefore, the crystals of hexa−coordinated l−argininato copper(II) complex with coordinated isothiocyanato ions, trans−[Cu(l−Arg)2(NCS)2]⋅2H2O (1), were synthesized and studied by X−ray structural analysis, spectroscopic techniques (FT−IR, Raman, X− and Q−band EPR, NIR−Vis−UV), magnetic and thermal methods. The distortion of elongated octahedron (T = 0.757) shows the static character. The complex presents a monomeric nature but the [Cu(l−Arg)2(NCS)2] units are bound via O‒H∙∙∙O, N‒H∙∙∙O and N‒H∙∙∙N hydrogen bonds forming two dimensional layers. One broad band with three well−marked maxima at 15,850 cm−1, 16,630 cm−1 and 17,500 cm−1 are generated by 2B1g(dx2-y2) → A1g(dz2), 2B2g(dxy) and 2Eg(dxz ≈ dyz) transitions. The values of g tensor components g⊥=gx=gy 2.056 (77 K) / 2.057 (298 K) agree well with the g⊥ found for other trans−N2O2 chromophore with two chelating l−Arg-ligands in copper(II) xy plane. The relation of gz (g||=2.245) >>gx=gy (g⊥= 2.056) > 2.0023 is characteristic for dx2-y2 orbital of unpaired electron ground state in the axial symmetry of copper(II) environment. The field induced slow magnetic relaxation is observed, despite the lack of the zero-field splitting of Cu(II) monomeric complex 1. Due to the labile character and the preference for distorted coordination geometries leading to plasticity of copper(II) coordination sphere, the comprehensive spectroscopic studies of the complexes arising in aqueous solutions when complex 1 was in aqueous solutions, were conducted (NIR−Vis−UV, EPR). The antimicrobial activity of 1 was evaluated against the yeast, dermatophyte and bacteria. Microsporum gypseum was the most sensitive strain, with a 4-time lower MIC comparing to the reference drug - Fluconazole.

Consistent Evaluation of Magnetic Exchange Couplings in Multicenter Compounds in KS-DFT: The Recomposition Method.

The use of broken-symmetry calculations in Kohn-Sham density functional theory has offered an affordable route to study magnetic exchange couplings in transition-metal-based compounds. However, computing this property in compounds exhibiting several couplings is still challenging and especially due to the difficulties to overcome the well-known problem of spin contamination. Here, we present a new and general method to compute magnetic exchange couplings in systems featuring several spin sites. To provide a consistent spin decontamination of J values, our strategy exploits the decomposition method of the magnetic exchange coupling proposed by Coulaud et al. and generalizes our previous work on diradical compounds where the overall magnetic exchange coupling is defined as the sum of its three main and properly extracted physical contributions (direct exchange, kinetic exchange, and spin polarization). In this aim, the generalized extraction of all contributions is presented to systems with multiple spin sites bearing one unpaired electron. This is done by proposing a new paradigm to treat the kinetic exchange contribution, which proceeds through monorelaxations of the magnetic orbitals. This method, so-called the recomposition method, is applied to a compound featuring three Cu(II) ions with a linear arrangement and to a recently synthesized complex containing a Cu4O4 cubane unit presenting an unusual magnetic behavior.

Photoelectron Spectroscopy and Theoretical Studies of Ge6MnO- Cluster with a MnV≡O Unit Interacting with a Double Aromatic Ge64- Ligand.

The structures and chemical bonding of Ge6MnO- are investigated using anion photoelectron spectroscopy and theoretical calculations. The lowest energy structure of Ge6MnO- is found to have a C5v symmetric structure with an O atom attached to a pentagonal bipyramidal MnGe6. Chemical bonding analyses reveal that Ge6MnO- can be considered as a [MnV≡O]3+[Ge64-] complex with two unpaired 3d electrons on Mn. The Ge64- ligand is highly stable in Ge6MnO- and exhibits double aromaticity with 10 delocalized σ electrons and 6 delocalized π electrons. Our calculations show that the Ge64- ligand could also form [CrIV≡O]2+[Ge64-] in Na2Ge6CrO and [FeIV≡O]2+[Ge64-] in Na2Ge6FeO. The results suggest the possibility of designing and synthesizing a series of stable high-valent metal oxide anionic species with the composition [M≡O]n+[Ge64-] in the gas phase or in the salt-stabilized bulk solid materials.

A Three-Dimensional Silicon-Diacetylene Porous Organic Radical Polymer

A Three-Dimensional Silicon-Diacetylene Porous Organic Radical Polymer

Resolving a Half-Century-Long Controversy between (Magneto)optical and EPR Spectra of Single-Electron-Reduced [PcFe]-, [PcFeL]-, and [PcFeX]2- Complexes: Story of a Double Flip.

The reduction of iron(II) phthalocyanine (Pc(2-)FeII) or its bisaxially coordinated complexes results in the formation of the purple/red [PcFe]-, [PcFeL]-, and [PcFeX]2- (L is neutral and X is anionic ligand) species. The X-ray structure of the [K(DME)4][PcFe] complex exhibits a square-planar [PcFe]- anion. 1H NMR spectra of the reduced species have one or two phthalocyanine broad peaks between 15 and 17 ppm. Solution magnetic moments are consistent with the presence of a single unpaired electron. A solid-state Mössbauer spectrum of [K(DME)4][PcFe] is consistent with an early report [Taube, R. Pure Appl. Chem.1974, 38, 427-438]. The solid-state EPR spectrum of the [PcFe]- anion is close to that recorded by Konarev et al. [ Dalton Trans.2012, 41, 13841-13847]. Solution EPR spectra of reduced species have axial symmetry (g⊥ ∼ 2.08-2.17 and g|| ∼ 1.95-1.96) and correlate well with spectra reported by Lever and Wilshire in 1978 [ Inorg. Chem.1978, 17, 1145-1151]. The UV-vis spectra of pentacoordinated [PcFeL]- and [PcFeX]2- anions consist of the characteristic bands around 810, 690, and 515 nm. These bands correlate well with the set of MCD pseudo A-terms and resemble transitions in the [Pc(3-)M]- and [Pc(3-)ML]- compounds. The UV-vis and MCD spectra of [PcFeL]- and [PcFeX]2- complexes are in stark contrast to the crystallographically characterized reference [Pc(2-)CoI]- anion, which is EPR silent, has a regular diamagnetic 1H NMR spectrum, and has an intense Q-band at 699 nm, which correlates well with the strong MCD A-term. The DFT and TDDFT calculations are suggestive of the iron(II) center in a (dxy)2(dxz,yz)3(dz2)1 (s = 1) electronic configuration that is antiferromagnetically coupled with the one-electron-reduced Pc(3-) ligand (i.e., [Pc(3-)FeII]-, [Pc(3-)FeIIL]-, and [Pc(3-)FeIIX]2-). The calculated EPR, Mössbauer, and UV-vis spectra of [PcFe]-, [PcFeL]-, and [PcFeX]2- complexes are in excellent agreement with the experimental data, thus resolving the controversy between axial s = 1/2 like EPR and Pc(3-)-like UV-vis spectra of these compounds.

Metal-semiconductor transition in Ψ-graphene

The effect of hydrogenation on the density of states (DOS), band structure, Pauli magnetic susceptibility (PMS), and electronic heat capacity (EHC) of Ψ -graphene is investigated within the nearest neighbor tight-binding model. Two different hydrogenation process of Ψ -graphene is examined: half hydrogenation ( Ψ -graphone) and full hydrogenation ( Ψ -graphane). It was observed that Ψ -graphone, like Ψ -graphene, exhibits metallic behavior, but it has sharp peaks in the DOS and corresponding flat bands in the band structure near the Fermi level, due to unpaired and localized electrons in its structure. Whereas, because of the strong σ bonds in the Ψ -graphane structure, a bandgap is created in its energy spectra. It can also be seen that with the hydrogenation of Ψ -graphene, the van-Hove singularities in the DOS and the number of sub-band in the band structures increased due to the greater overlap of the orbitals. These lead to the crossovers in the PMS and the Schottky anomaly peaks in the EHC, which both of these peaks are observed in the Ψ -graphane curve at a higher temperature than the other two structures. These results indicate that the hydrogenation of Ψ -graphene leads to a metal-to-semiconductor transition.

Magnetoresistive Single‐Molecule Junctions: the Role of the Spinterface and the CISS Effect

AbstractThis review is an effort in putting together the latest results about room‐temperature magnetoresistive (MR) effects in nanoscale/single‐molecule electronic devices consisting of one (few) molecule(s) placed in electrical contact between two nanoscale electrodes. Molecules represent powerful building blocks for developing state‐of‐the‐art MR devices, as they bring long spin relaxation timescales, low cost and high tunability of their electrical and magnetic properties via chemical modifications. The capability to control at room temperature and under bespoke electrodes’ magnetization the MR response of a single‐molecule (SM) device has been a longstanding quest. Such SM platforms could serve as fundamental tools to understand what the main mechanistic ingredients of MR effects in a molecular device are, leading to their use as building‐blocks for miniaturization in spintronic applications. The work carried out so far in this field has identified two key components directly involved in the MR response of a single(few)‐molecule(s) device: (i) The molecule|electrode spinterface, defining the interplay between interfacial electrostatics and spin density, has been proven to play a fundamental role in the interpretation of the observed single‐molecule junction's MR effects, which is governed by the electrode material and the electrode‐molecule chemistry. (ii) Two aspects of the molecular structure have been demonstrated to be involved in the spin‐dependent conduction mechanism: (1) the presence of paramagnetic metal centres in the molecular structure and how their orbitals bearing the unpaired electrons couple with the device electrodes, and (2), the degree of chirality within the molecular wire. This contribution will focus on the above points (i‐ii) by making use of specific examples in the literature.

ANALYSIS OF DPPH AND MnCl₂ USING ELECTRON PARAMAGNETIC RESONANCE (EPR) SPECTROSCOPY

EPR spectroscopy, in a constant-frequency field-swept experiment, was used to determine the resonant magnetic field, g-factor, line width, and hyperfine constant for diphenyl picrylhydrazyl at room temperature and manganese (II) chloride at cryogenic temperatures (using liquid nitrogen). Diphenyl picrylhydrazyl was determined to be a free radical, indicated by a g-factor of 2.022, with a resonant magnetic field of 3.23 kG at a microwave frequency of 9.14 GHz. The manganese (II) chloride was found to have six signal peaks, indicating hyperfine interaction of a nucleus with non-zero spin with unpaired electrons (spin was determined to be 5/2).

Exploring the Ni 3d Orbital Unpaired Electrons Induced Polarization Loss Based on Ni Single‐Atoms Model Absorber

AbstractSingle‐atoms (SAs) strategies have been proved to be effective in modulating electromagnetic wave (EMW) absorption, however, the establishment of a definitive relationship between metal SAs electronic configurations and physical loss mechanisms has been still absent, especially on the atomic scale. Herein, stable Ni‐SAsx/N‐doped carbon (NC) absorbers are fabricated with the strategy of ligand polymerization. The morphology, composition, electrical conductivity, defects, and electronic interactions of the material can be well tailored by Ni species modulation engineering. Theoretical and experimental results show that the atomically dispersed individual Ni atoms contribute to enhanced EMW absorption performance through excess Ni 3d orbital unpaired electron induced polarization loss. Benefiting from it, Ni‐SAs3/NC with the highest Ni SAy‐Nx (y &gt; 1, x &gt; 1) polar/defect centers exhibit excellent EMW absorption with an effective absorption bandwidth of 7.08 GHz at a matched thickness of 2.50 mm. Radar cross‐section simulations further demonstrate its potential for practical application as EMW absorber. This study reveals the continuous evolution of microscopic electromagnetic loss mechanism (i.e., conduction loss→ unique polarization loss→ conduction loss) for the first time, which provides insight into the deep design of absorbers from atom‐scale view.

Elucidating Λ-doublet splittings and rotational quantum number-dependent collisional broadenings in 2∏1/2 and 2∏3/2 spin-split sub-bands of NO at 5.2 µm

High-resolution ro-vibrational spectroscopic features of nitric oxide (NO) are particularly interesting because of the unpaired electron and non-zero nuclear spin of the nitrogen atom. Here, ultra-sensitive cavity ring-down spectroscopy (CRDS) coupled with an external-cavity quantum cascade laser (EC-QCL) radiation source was employed to measure the rotationally-resolved fine structure Λ-doublet splittings between the parity doublet e and f components in the (2∏1/2 - 2∏1/2) and (2∏3/2 - 2∏3/2) allowed sub-bands of the v = 1 ← 0 fundamental vibrational band of NO molecule near 5.2 µm. Subsequently, we determined several principal spectroscopic parameters such as the Λ-doubling constants, vibrational transition dipole moments and the Herman-Wallis coefficients for both e and f Λ-doublet components by probing various R-branch rotational lines (J = 0.5 to 23.5) of the studied spin-split sub-bands of NO associated with spin–orbit interaction. In addition, we performed the pressure broadening effect on the Λ-doublet splittings in collision with three vital perturbing gases at room temperature (296 K) and accurately determined the pressure broadening coefficients, γi (e,f) in cm-1atm−1 [(i = He, Ar and Zero air (mainly N2 + O2)] along with their dependence on the rotational quantum number (J). We observed the pronounced collision-induced rotational quantum effect and the result of rotationally inelastic collision in the system for each collision partner. All these measured high-resolution new spectroscopic parameters over 33 ro-vibrational transitions via an EC-QCL based CRDS method will help significantly in interpreting fundamental molecular properties of this diatomic NO molecule.

Evaluating the detection and trapping of small gas molecules on hydrogenated siligene

The use of new two-dimensional systems to detect and capture organic molecules remains a vital research area. In this work, we have investigated, by first-principles calculations, the feasibility of using a hydrogenated siligene (HSiGeH) monolayer to detect and capture small gas molecules through a self-propagating reaction mechanism. We have studied the adsorption of formaldehyde (CH2O), acetylene (C2H2), and ethylene (C2H4) on an HSiGeH monolayer with an H-vacancy (including two situations: an H-vacancy on a Si or a Ge atom). In each case, the molecule chemisorbs at the H-vacancy, increasing the C–O or C–C bond lengths, indicating that double and triple bonds of the molecule are partially broken, resulting in unpaired electrons in one C atom of each molecule. We have found that the hydrogenated chemisorbed molecule -with a new H-vacancy formed on the surface- is the most energetically favorable configuration for each reaction. The viability of the reactions was analyzed by describing the minimum energy path (MEP) computed by the climbing image nudged elastic band method (CI-NEB). Our results show that the self-propagating reaction is viable except for one case, where the C2H4 chemisorbs on the monolayer with the H-vacancy on Ge. These results point toward the application of the HSiGeH monolayer as a possible system for novel gas-removal systems.

Current density functional framework for spin–orbit coupling

Relativistic two-component density functional calculations are carried out in a non-collinear formalism to describe spin-orbit interactions, where the exchange-correlation functional is constructed as a generalization of the non-relativistic density functional approximation. Contrary to non-relativistic density functional theory (DFT), spin-orbit coupling, however, leads to a non-vanishing paramagnetic current density. Density functionals depending on the kinetic energy density, such as meta-generalized gradient approximations, should therefore be constructed in the framework of current DFT (CDFT). The latter has previously exclusively been used in the regime of strong magnetic fields. Herein, we present a consistent CDFT approach for relativistic DFT, including spin-orbit coupling. Furthermore, we assess the importance of the current density terms for ground-state energies, excitation energies, nuclear magnetic resonance shielding, and spin-spin coupling constants, as well as hyperfine coupling constants, Δg-shifts, and the nuclear quadrupole interaction tensor in electron paramagnetic resonance (EPR) spectroscopy. The most notable changes are found for EPR properties. The impact of the current-dependent terms rises with the number of unpaired electrons, and consequently, the EPR properties are more sensitive toward CDFT. Considerable changes are observed for the strongly constrained and appropriately normed functionals, as well as the B97M family and TASK. The current density terms are less important when exact exchange is incorporated. At the same time, the current-dependent kernel ensures the stability of response calculations in all cases. We, therefore, strongly recommend to use the framework of CDFT for self-consistent spin-orbit calculations.

A recursive formulation of one‐electron coupling coefficients for spin‐adapted configuration interaction calculations featuring many unpaired electrons

AbstractThis work reports on a novel computational approach to the efficient evaluation of one‐electron coupling coefficients as they are required during spin‐adapted electronic structure calculations of the configuration interaction type. The presented approach relies on the equivalence of the representation matrix of excitation operators in the basis of configuration state functions and the representation matrix of permutation operators in the basis of genealogical spin eigenfunctions. After the details of this connection are established for every class of one‐electron excitation operator, a recursive scheme to evaluate permutation operator representations originally introduced by Yamanouchi and Kotani is recapitulated. On the basis of this scheme we have developed an efficient algorithm that allows the evaluation of all nonredundant coupling coefficients for systems with 20 unpaired electrons and a total spin of within only a few hours on a simple Desktop‐PC. Furthermore, a full‐CI implementation that utilizes the presented approach to one‐electron coupling coefficients is shown to perform well in terms of computational timings for CASCI calculations with comparably large active spaces. More importantly, however, this work paves the way to spin‐adapted and configuration driven selected configuration interaction calculations with many unpaired electrons.

Enhancement of magnetic properties of Sm-Co nano composite ribbons by heavy lanthanide doping

Sm-Co magnets becoming more and more interesting among research community since 1950′s due to its essential role in space and transport industry to be used in some precious instruments such as, sensors, actuators, motors, and gyroscope. The combination of Rare-earth (RE) and Transition metal (TM) is an ideal combination to make a high-performance magnet, as the RE provides the high magneto crystalline anisotropy (HA) and the TM provides the high magnetization (Ms) and high Curie temperature (Tc). SmCo5 compound possesses Tc as high as ∼ 700 °C. Previous studies have reported that HRE (Gd, Dy, Er and Ho) could be used as a temperature compensation material as unpaired 4f electrons in shell gives rise to maximum magnetic moment. In this study, effect of lanthanides (HREs - Gd and/ Dy) on microstructure and magnetic properties of Sm-Co-based rapidly solidified alloy ribbons have been reported. Phase analyses confirmed the presence of 1:5H phase which was prevalent along with a fraction of 2:17R phase in all the alloy ribbons. Hc value was increased from 10.9 to 13.3 kOe (1.09 to 13.3 T) and Br value was increased from 12.5 to 16.2 kG (1.25 to 1.62 T) with Dysprosium addition.