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Spin state is often regarded as the crucial valve to release the reactivity of energy‐related catalysts, yet it is also challenging to precisely manipulate, especially for the active center ions occupied at the specific geometric sites. Herein, a π–π type orbital coupling of 3d (Co)‐2p (O)‐4f (Ce) was employed to regulate the spin state of octahedral cobalt sites (CoOh) in the composite of Co3O4/CeO2. More specifically, the equivalent high‐spin ratio of CoOh can reach to 54.7 % via tuning the CeO2 content, thereby triggering the average eg filling (1.094) close to the theoretical optimum value. The corresponding catalyst exhibits a superior water oxidation performance with an overpotential of 251 mV at 10 mA cm−2, rivaling most cobalt‐based oxides state‐of‐the‐art. The π–π type coupling corroborated by the matched energy levels between Ce t1u/t2u‐O and CoOh t2g‐O π type bond in the calculated crystal orbital Hamilton population and partial density of states profiles, stimulates a π‐donation between O 2p and π‐symmetric Ce 4fyz2 orbital, consequently facilitating the electrons hopping from t2g to eg orbital of CoOh. This work offers an in‐depth insight into understanding the 4f and 3d orbital coupling for spin state optimization in composite oxides. [ABSTRACT FROM AUTHOR]

Spin state is often regarded as the crucial valve to release the reactivity of energy‐related catalysts, yet it is also challenging to precisely manipulate, especially for the active center ions occupied at the specific geometric sites. Herein, a π–π type orbital coupling of 3d (Co)‐2p (O)‐4f (Ce) was employed to regulate the spin state of octahedral cobalt sites (CoOh) in the composite of Co3O4/CeO2. More specifically, the equivalent high‐spin ratio of CoOh can reach to 54.7 % via tuning the CeO2 content, thereby triggering the average eg filling (1.094) close to the theoretical optimum value. The corresponding catalyst exhibits a superior water oxidation performance with an overpotential of 251 mV at 10 mA cm−2, rivaling most cobalt‐based oxides state‐of‐the‐art. The π–π type coupling corroborated by the matched energy levels between Ce t1u/t2u‐O and CoOh t2g‐O π type bond in the calculated crystal orbital Hamilton population and partial density of states profiles, stimulates a π‐donation between O 2p and π‐symmetric Ce 4fyz2 orbital, consequently facilitating the electrons hopping from t2g to eg orbital of CoOh. This work offers an in‐depth insight into understanding the 4f and 3d orbital coupling for spin state optimization in composite oxides. [ABSTRACT FROM AUTHOR]

Iron‐based single‐atom catalysts (Fe─N─C) exhibit excellent oxygen reduction activity but struggle with bifunctional performance due to their poor oxygen evolution activity. Although the Fe spin state is found to be closely associated with enhanced bifunctional activity, controllably regulating the Fe spin state remains a challenge. Here, the controllable regulation of Fe spin state is directly achieved through competitive coordination between chlorine and pyridine nitrogen in the axial direction of Fe─N4. The spin state of Fe is regulated from high spin to intermediate spin by the modulation of axial ligands from weak‐field ligand chlorine to strong‐field ligand pyridinic nitrogen, which leads to the enhanced bifunctional activity of N─FeN4 with a small potential gap (ΔE = 0.68 V). Theoretical calculations indicate that the spin state turning is accompanied by an enhanced binding strength between Fe sites and *OH leading to a significant decrease in the OER barrier. Moreover, N─FeN4 exhibits sufficient durability for oxygen reduction reaction (ORR) (over 50 h), oxygen evolution reaction (OER) (over 200 h), and the assembled zinc–air battery (over 1000 h). Here a novel approach is proposed for designing efficient catalysts based on spin state and profound insights into Fe─N─C spin state for bifunctional oxygen catalysis. [ABSTRACT FROM AUTHOR]

Due to structural complexity and limited understanding, precise chemical modification in atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts requires theoretical calculations to optimize electronic, geometric, and catalytic performance and experimental implementation of learned lessons to improve their catalytic performance towards oxygen reduction reaction (ORR). Herein, we conducted a density functional theory (DFT) investigation to understand the effect of the replacement of O-atoms in Fe–O 4 –C by N-atoms in the first coordination shell of Fe-site (constructing five models: Fe–O 4 –C, Fe–O 3 N–C, Fe–N 2 O 2 –C, Fe–ON 3 –C and Fe–N 4 –C) towards ORR. The geometric and electronic calculations of these models suggested that replacing all the O-atoms with N-atoms around the Fe-site would make it more conducive to the adsorption of ORR intermediates. Moreover, the Gibbs free energy calculations demonstrated that the Fe-site becomes the active centre for 2e− ORR, leading to the dominant generation of H 2 O 2 when Fe is coordinated with four O-atoms (Fe–O 4 –C). Whereas in compounds like Fe–N 2 O 2 –C, Fe–O 3 N–C, and Fe–N 4 –C, where the Fe-site displays 4e− ORR, form water is a preferred product if the O-atoms are replaced by N-atoms, as in Fe–N 2 O 2 –C, Fe–O 3 N–C, and Fe–N 4 –C. This study would provide a fundamental understanding of how atomically dispersed M-N-C catalysts' electrocatalytic activity is affected by changes in the coordination environment of metal sites. [Display omitted] • A theoretical approach was used to construct the models of Fe-NxOy-C-based electrocatalysts. • The models Fe–O 4 –C, Fe–NO 3 –C, M–N 2 O 2 –C, M–N 3 O–C, and M-N4-C, were completely investigated via DFT approaches. • The O 2 adsorption at the Fe–N 4 –C catalyst was the determining step during the associative pathway. • The M-N 4 -C catalytic moel displayed 4e- ORR, while the M-O 4 -C catalyst showed 2e- ORR. [ABSTRACT FROM AUTHOR]

Using scanning tunneling microscopy and spectroscopy we demonstrate a revival of magnetism in 7-armchair nanoribbon by unpassivated atoms at the termini. Namely, a pair of intense Kondo resonances emerges at the peripheries of zigzag terminus revealing the many-body screening effects of local magnetic moments. Although Kondo resonance originates from a missing local orbital, it extends to a distance of 2.5 nm along the edge of the ribbon. The results are complemented by density functional theory calculations which suggest a possible coupling between Kondo states despite screening effects of substrate electrons. These findings indicate a possibility to restore intrinsic magnetic ordering in graphene nanoribbon without major structural modifications. [ABSTRACT FROM AUTHOR]

This study explores the optical properties of monolayers from transition metal dichalcogenides (TMDs), materials that have gained attention post-graphene discovery for their unique electronic and optical characteristics. We analyze the crystal structure, Brillouin zones, and electronic band structures of TMD monolayers, laying the foundation to understand their diverse optical phenomena. Special emphasis is placed on the energy spectrum across valleys and the use of an effective Hamiltonian for parallel spin bands. We investigate interband optical transitions, including single-, two-, and three-photon processes, developing equations to calculate transition probabilities that take into account polarization, light frequency, and temperature. Our theoretical analysis, rooted in quantum mechanics, sheds light on the matrix elements that dictate these transitions, underscoring the impact of complex compositions on the optical behavior of TMD monolayers. This work not only advances our understanding of TMD optical properties but also highlights their potential for optoelectronic applications, marking a significant contribution to the field of semiconductor physics. [ABSTRACT FROM AUTHOR]

Molecular level understanding of 3d-transition metal interaction with water molecules in various electronic states is of fundamental significance in chemistry and biology. This study systematically presents the propensity of 3d-transition metals in their variable electronic and spin states towards solvation and splitting water molecules. The topological analysis affirmed that neutral and mono-cationic complexes are prone to be partially covalent in nature from moving low to high spin states; however, coordinate bonding is observed in di- and tri-cationic ion–water complexes. Potential energy surface analysis showed a profound influence of electronic states of 3d-transition metals on the relative feasibility of bond scission and solvation competing pathways. The early neutral, high spin mono-cationic, and di-cationic transition metals prefer solvation over splitting the water molecule. Similarly, mid- and late-transition metal ions in the first two electronic states, irrespective of the spin state, show higher preferences towards solvation. In contrast, neutral and tri-cationic ions tend to form either insertion complexes, hydroxides, or hydrides over the ion–water complexes, suggesting a preference to split the water molecule. Thus, tuning the electronic and micro-environment will help in the design of transition metals catalysts for water splitting. [ABSTRACT FROM AUTHOR]

Metasurfaces are a class of planar optical components that are engineered to manipulate electromagnetic waves, including their spin states in terms of circular polarizations. For example, the Pancharatnam–Berry (PB) phase has been exploited in metasurfaces for various spin functionalities, but these spin functionalities, exhibit conjugate relations for spin states. Recent advances combining the PB phase and propagation phase have implemented completely independent spin functionalities for spin states. However, the spin functionalities are fixed once the metasurfaces are designed. Here, this work proposes and demonstrates that the spin functionalities designed from the PB phase and propagation phase can be further extended by simply rotating the elements in a metasurface. This extension is based on a relationship between phase profiles of spin states that are acquired before and after the rotation. Proof‐of‐concept demonstrations are performed for the extended spin functionalities, including the conversion from spin angular momentum to orbital angular momentum, and spin‐dependent holograms. This extension may find use in relevant applications such as polarized display and dual‐polarized holography. [ABSTRACT FROM AUTHOR]

The solution of the Dirac equation with the Coulomb potential is used to analyze bound electron states in a hydrogen atom. The analysis is based on the fact that such states are characterized by a set of quantum numbers which describe definite values of the complete set of physical quantities that can be determined simultaneously. This set includes the energy, square of the total angular momentum, one of its component and a spinor invariant. The latter, spinor invariant gives two-valued quantum number which determines the sign of its eigenvalue. In addition to the known Dirac and Johnson–Lippman invariant, there exists a new one. Operators of these three spinor invariants do not commute between themselves which results in the degeneracy of the energy levels with respect to the two-valued quantum number. Three different systems of the eigenbispinor corresponding to the three spinor invariants are obtained and the generalized solution with free parameters is calculated. Variation of the free parameters transforms one particular solution into any other. It is shown that the electron probability densities and spin polarizations in an electron cloud depend essentially on the invariant set, demonstrating physical difference of the states corresponding to different spinor invariants. [ABSTRACT FROM AUTHOR]

We choose a typical three-site one-dimensional (1D) quantum chain system to deduce exact spin states and nonequilibrium spin transport properties analytically. The initial spin-up and spin-down electron charges on each site of the chain are calculated from the exactly derived spin ground state with the assumption of half-filling. Based on the Keldysh formalism, we describe the basic theoretical methods and derive some analytic formulas (differential spin conductance, spin transport current, electron charge distribution, etc.) for nonequilibrium spin transport of the 1D chain systems within the Hartree–Fock approximation when Coulomb electron interaction is present. The scattering processes including Coulomb repulsion between the spin-up and spin-down electrons, and spin–spin interactions due to spin degrees freedom are taken into account. We also report the numerical results of the nonequilibrium spin transport of the three-site 1D chain system in some special cases using the initial spin-up/down electron charges. [ABSTRACT FROM AUTHOR]

Heteroatom doped atomically dispersed Fe1‐NC catalysts have been found to show excellent activity toward oxygen reduction reaction (ORR). However, the origin of the enhanced activity is still controversial because the structure‐function relationship governing the enhancement remains elusive. Herein, sulfur(S)‐doped Fe1‐NC catalyst was obtained as a model, which displays a superior activity for ORR towards the traditional Fe‐NC materials. 57Fe Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy revealed that incorporation of S in the second coordination sphere of Fe1‐NC can induce the transition of spin polarization configuration. Operando 57Fe Mössbauer spectra definitively identified the low spin single‐Fe3+‐atom of C‐FeN4‐S moiety as the active site for ORR. Moreover, DFT calculations unveiled that lower spin state of the Fe center after the S doping promotes OH* desorption process. This work elucidates the underlying mechanisms towards S doping for enhancing ORR activity, and paves a way to investigate the function of broader heteroatom doped Fe1‐NC catalysts to offer a general guideline for spin‐state‐determined ORR. [ABSTRACT FROM AUTHOR]

Heteroatom doped atomically dispersed Fe1‐NC catalysts have been found to show excellent activity toward oxygen reduction reaction (ORR). However, the origin of the enhanced activity is still controversial because the structure‐function relationship governing the enhancement remains elusive. Herein, sulfur(S)‐doped Fe1‐NC catalyst was obtained as a model, which displays a superior activity for ORR towards the traditional Fe‐NC materials. 57Fe Mössbauer spectroscopy and electron paramagnetic resonance spectroscopy revealed that incorporation of S in the second coordination sphere of Fe1‐NC can induce the transition of spin polarization configuration. Operando 57Fe Mössbauer spectra definitively identified the low spin single‐Fe3+‐atom of C‐FeN4‐S moiety as the active site for ORR. Moreover, DFT calculations unveiled that lower spin state of the Fe center after the S doping promotes OH* desorption process. This work elucidates the underlying mechanisms towards S doping for enhancing ORR activity, and paves a way to investigate the function of broader heteroatom doped Fe1‐NC catalysts to offer a general guideline for spin‐state‐determined ORR. [ABSTRACT FROM AUTHOR]

We present herein the magnetic and Mössbauer investigation of a colorimetric chemical sensor with the chemical formula [Fe(H2btm)2(H2O)2]Cl2 (1) (H2btm = Di(1H-tetrazol-5-yl)methane). The spectra were recorded before and after sensing a series of toxic gases (MeOH, diethylenetriamine, hexylamine, 1,2-diaminocyclohexane, 3-picolylamine, pyridine and furfurylamine). Worth to note that the sensing process (color changes) proceeds at room temperature, does not require any pretreatment and can be detected as well by the naked eyes. 57Fe Mössbauer spectroscopy not only allows to identify the nature of spin states involved in our Fe(II) sensor but also to evaluate quantitatively the respective spin state population, i.e. high spin and low-spin states. [ABSTRACT FROM AUTHOR]

The electronic and geometric structures of the water‐oxidizing complex of photosystem II in the steps of the catalytic cycle that precede dioxygen evolution remain hotly debated. Recent structural and spectroscopic investigations support contradictory redox formulations for the active‐site Mn4CaOx cofactor in the final metastable S3 state. These range from the widely accepted MnIV4 oxo‐hydroxo model, which presumes that O−O bond formation occurs in the ultimate transient intermediate (S4) of the catalytic cycle, to a MnIII2MnIV2 peroxo model representative of the contrasting "early‐onset" O−O bond formation hypothesis. Density functional theory energetics of suggested S3 redox isomers are inconclusive because of extreme functional dependence. Here, we use the power of the domain‐based local pair natural orbital approach to coupled cluster theory, DLPNO‐CCSD(T), to present the first correlated wave function theory calculations of relative stabilities for distinct redox‐isomeric forms of the S3 state. Our results enabled us to evaluate conflicting models for the S3 state of the oxygen‐evolving complex (OEC) and to quantify the accuracy of lower‐level theoretical approaches. Our assessment of the relevance of distinct redox‐isomeric forms for the mechanism of biological water oxidation strongly disfavors the scenario of early‐onset O−O formation advanced by literal interpretations of certain crystallographic models. This work serves as a case study in the application of modern coupled cluster implementations to redox isomerism problems in oligonuclear transition metal systems. [ABSTRACT FROM AUTHOR]

We report the single crystal XRD and MicroED structure, magnetic susceptibility, and EPR data of a series of CaMn3IVO4 and YMn3IVO4 complexes as structural and spectroscopic models of the cuboidal subunit of the oxygen‐evolving complex (OEC). The effect of changes in heterometal identity, cluster geometry, and bridging oxo protonation on the spin‐state structure was investigated. In contrast to previous computational models, we show that the spin ground state of CaMn3IVO4 complexes and variants with protonated oxo moieties need not be S=9/2. Desymmetrization of the pseudo‐C3‐symmetric Ca(Y)Mn3IVO4 core leads to a lower S=5/2 spin ground state. The magnitude of the magnetic exchange coupling is attenuated upon oxo protonation, and an S=3/2 spin ground state is observed in CaMn3IVO3(OH). Our studies complement the observation that the interconversion between the low‐spin and high‐spin forms of the S2 state is pH‐dependent, suggesting that the (de)protonation of bridging or terminal oxygen atoms in the OEC may be connected to spin‐state changes. [ABSTRACT FROM AUTHOR]

We report the single crystal XRD and MicroED structure, magnetic susceptibility, and EPR data of a series of CaMn3IVO4 and YMn3IVO4 complexes as structural and spectroscopic models of the cuboidal subunit of the oxygen‐evolving complex (OEC). The effect of changes in heterometal identity, cluster geometry, and bridging oxo protonation on the spin‐state structure was investigated. In contrast to previous computational models, we show that the spin ground state of CaMn3IVO4 complexes and variants with protonated oxo moieties need not be S=9/2. Desymmetrization of the pseudo‐C3‐symmetric Ca(Y)Mn3IVO4 core leads to a lower S=5/2 spin ground state. The magnitude of the magnetic exchange coupling is attenuated upon oxo protonation, and an S=3/2 spin ground state is observed in CaMn3IVO3(OH). Our studies complement the observation that the interconversion between the low‐spin and high‐spin forms of the S2 state is pH‐dependent, suggesting that the (de)protonation of bridging or terminal oxygen atoms in the OEC may be connected to spin‐state changes. [ABSTRACT FROM AUTHOR]

Circular dichroism, as one of the exotic phenomena, derives from chirality biomolecules in nature, expressing differential absorption of spin angular momentum. The concept of dichroism has been migrated to the field of artificial materials and acquired adequate development. However, there is still a lack of a flexible strategy to tailor circular dichroism for providing another promising level to achieve spin‐selective multi‐dimensional manipulation of electromagnetic waves. In this work, a paradigm of reflective chiral metasurface is proposed to promote this aspect of exploration. By introducing loss resistors into the chiral meta‐atoms, the magnitude of differential absorption effect can be tailored by varying the corresponding resistance, leading to the variation of co‐polarization reflection amplitude. Combining with the Pancharatnam–Berry phases of chiral meta‐atom, both the reflective amplitude and phase are flexibly controlled in independent manners. Accordingly, the pattern of reflection fields can be theoretically shaped into arbitrary forms through Fourier transform in spatial domain. Here, metasurfaces for achieving rectangular‐shaped beam and complex‐amplitude hologram are demonstrated as two proofs‐of‐principle. Encouragingly, this effort provides an alternative approach for simultaneous control of amplitude and phase, which may pave a new route in the fields of beam‐forming technology and spin‐selective integrated systems. [ABSTRACT FROM AUTHOR]

[Display omitted] Photoelectrochemical (PEC) water splitting for solar energy conversion into chemical fuels has attracted intense research attention. The semiconductor hematite (α-Fe 2 O 3), with its earth abundance, chemical stability, and efficient light harvesting, stands out as a promising photoanode material. Unfortunately, its electron affinity is too deep for overall water splitting, requiring additional bias. Interface engineering has been used to reduce the onset potential of hematite photoelectrode. Here we focus instead on energy band engineering hematite by shrinking the crystal lattice, and the water-splitting onset potential can be decreased from 1.14 to 0.61 V vs. the reversible hydrogen electrode. It is the lowest record reported for a pristine hematite photoanode without surface modification. X-ray absorption spectroscopy and magnetic properties suggest the redistribution of 3 d electrons in the as-synthesized grey hematite electrode. Density function theory studies herein show that the smaller-lattice-constant hematite benefits from raised energy bands, which accounts for the reduced onset potential. [ABSTRACT FROM AUTHOR]

The Infrared (IR) and Raman spectra of various interstitial carbon defects in silicon are computed at the quantum mechanical level by using an all electron Gaussian type basis set, the hybrid B3LYP functional and the supercell approach, as implemented in the CRYSTAL code (Dovesi et al. J. Chem. Phys. 2020, 152, 204111). The list includes two 〈100〉 split interstitial IXY defects, namely ICC and ICSi, a couple of related defects that we indicate as IXIY, the so called CiCs0 in its A and B form, as well as SiCiSi and CsCiCs, in which the interstitial carbon atom is twofold coordinated. The second undergoes a large relaxation, and the final configuration is close to ICCCs. Geometries, relative stabilities, electronic, and vibrational properties are analysed. All these defects show characteristic features in their IR spectrum (above 730 cm−1), whereas the Raman spectrum is dominated, in most of the cases, by the pristine silicon peak at 530 cm−1, that hides the defect peaks. [ABSTRACT FROM AUTHOR]

Guiding electromagnetic waves carrying spin angular momentum is an important issue in both optical and microwave communities that thus has intrigued enormous interest in the past few decades. In particular, asymmetrical propagation is seriously considered as a possibility to push the development of encryption communication and electromagnetic circulators, which is a hot area but still a challenge. Circular dichroism, referring to differential absorption of distinct polarization states, provides an alternative scheme to achieve asymmetric propagation in a spin‐correlated way. Here, a paradigm of obtaining broadband asymmetric reflection to push the exploration in this aspect is proposed. With this aim, an N‐shaped resonator loaded with two lumped resistors is designed as a meta‐atom to reveal the amplitude flipping of nearly 0 and 1 for distinct polarization states. Combining with Pancharatnam–Berry phases, the arbitrary phase profile of a designated spin state can be achieved. As a proof‐of‐principle, a robust meta‐mirror is fabricated to acquire broadband electromagnetic focusing under the illumination of left‐handed circularly polarized (LHCP) wave. On the other hand, the reflection of right‐handed circularly polarized (RHCP) wave is substantially suppressed. Both numerical simulation and experimental measurement are carried out to demonstrate the feasibility of this system. [ABSTRACT FROM AUTHOR]

• The Fe spin state of Fe(II)Cl 2 (tpm) has been studied by experimental and theoretical investigation. • Theoretical investigation are performed on XAS at the Fe L 2,3 -edges and N K-edge. • The best agreement has been obtained for a low-spin, diamagnetic ground state. • The stability depends upon the ligands, the bulk solvent and the interaction of the vacant site. • Both tpm→Fe(II) σ bonding and a tpm⟵Fe(II) Charge Transfer characterize the Fe–tpm interaction. The Fe(II) spin state in the condensed phase of [Fe(II)Cl2(tpm)] (tpm = [tris(pyrazol-1-yl)methane]; 1) catalyst has been determined through a combined experimental and theoretical investigation of X-Ray Absorption Spectroscopy (XAS) at the FeL 2,3 -edges and NK-edge. Results indicated that in this phase a mixed singlet/triplet state is plausible. These results have been compared with the already know Fe singlet spin state of the same complex in water solution. A detailed analysis of the electronic structure and bonding mechanism of the catalyst showed that the preference for the low-spin diamagnetic ground state, strongly depends upon the ligands, the bulk solvent and the interaction of the complex's vacant site (the sixth) with a further ligand. Moreover, comparison of the electronic properties of the complex in condensed phase and water solution showed an increased Lewis acidity of the catalyst in solution phase, due to a decreasing of the LUMO energy of about 8 kcal/mol. These results gave an overall picture of the electronic behavior of the complex investigated, on going from condensed to water solution phase, explaining the preferred use of 1 as catalyst in homogeneous catalysis. The N Fe(II) interaction has been thoroughly investigated by means of DFT Kohn-Sham and EDA bond analysis applied to i) the isolated [Fe(II)Cl 2 (tpm)] and ii) the [Fe(II)Cl 2 (tpm)] interacting with water as a solvent within the Conductor-like Screening Mode (COSMO) framework. Results showed that both tpm→Fe(II) σ and tpm⟵Fe(II) π Charge Transfer (CT) interactions characterize the Fe(II)–tpm interaction. Moreover, the three tpm N atoms do not equally interact with the Fe(II) and one of them shares a suitable available iron-based d virtual orbital, to bind a further ligand in trans position. [ABSTRACT FROM AUTHOR]

Carbenes are challenging molecular species for quantum chemistry because of the energetic proximity of their singlet and triplet spin states and the sensitive dependence of spin-state energetics on the geometry of the carbene site. Here we use an extended set of aryl-carbenes to evaluate the performance of density functional theory (DFT) approximations as well as of wave function based perturbation theory approaches (orbital-optimised perturbation theory methods OO-MP2 and OO-SCS-MP2) against reference coupled cluster calculations with singles, doubles and perturbative triples conducted with the aid of the domain-based local pair natural orbitals approach, DLPNO-CCSD(T). In addition to the expected functional dependence, our results document a remarkable discordance in the performance of DFT methods in the sense that the functionals that yield the best geometries do not coincide with those that provide the best spin-state energetics. Analysis of the results allows us to propose a series of methods that are expected to perform reliably within certain confidence limits for the title systems. Additionally, methodological issues regarding the reference singlet–triplet gaps obtained by the DLPNO-CCSD(T) approach are discussed. [ABSTRACT FROM AUTHOR]

Extensive high‐level quantum‐chemical calculations reveal that the rod‐shaped molecule BeOBeC, which was recently generated in matrix experiments, exists in two nearly isoenergetic states, the 5Σ quintet (56) and the 3Σ triplet (36). Their IR features are hardly distinguishable at finite temperature. The major difference concerns the mode of spin coupling between the terminal beryllium and carbon atoms. Further, the ground‐state potential‐energy surface of the [2Be,C,O] system at 4 K is presented and differences between the photochemical and thermal behaviors are highlighted. Finally, a previously not considered, so far unknown C2v‐symmetric rhombus‐like four‐membered ring 3[Be(O)(C)Be] (35) is predicted to represent the global minimum on the potential‐energy surface. [ABSTRACT FROM AUTHOR]

Extensive high‐level quantum‐chemical calculations reveal that the rod‐shaped molecule BeOBeC, which was recently generated in matrix experiments, exists in two nearly isoenergetic states, the 5Σ quintet (56) and the 3Σ triplet (36). Their IR features are hardly distinguishable at finite temperature. The major difference concerns the mode of spin coupling between the terminal beryllium and carbon atoms. Further, the ground‐state potential‐energy surface of the [2Be,C,O] system at 4 K is presented and differences between the photochemical and thermal behaviors are highlighted. Finally, a previously not considered, so far unknown C2v‐symmetric rhombus‐like four‐membered ring 3[Be(O)(C)Be] (35) is predicted to represent the global minimum on the potential‐energy surface. [ABSTRACT FROM AUTHOR]

We present results of soft X-ray absorption spectroscopy studies of EuBaCo 2 O 5.5 powders subjected to mechanical impact (milling in a ball mill). We show that in the near-surface region (5–10 nm) of particles of the powder, EuBaCo 2 O 5.5 decomposes into Co 3 O 4 , BaCO 3 , and EuCoO 3. A knowledge of the low-spin state of Co3+ ions in EuCoO 3 and Co 3 O 4 and possibilities of surface-sensitive soft X-ray absorption spectroscopy have allowed to determine the composition of the EuBaCo 2 O 5.5 sample subjected to mechanical impact near its surface, which is inaccessible to standard X-ray phase analysis. Unlabelled Image • EuBaCo 2 O 5.5 powders are subjected to mechanical impact in a ball mill. • The samples are studied by surface-sensitive soft X-ray absorption spectroscopy. • Products of reaction in the near-surface area are Co 3 O 4 , BaCO 3 , and EuCoO 3. • Co3+ ions in EuCoO 3 are in a low-spin state. [ABSTRACT FROM AUTHOR]

We discuss the possibility to formulate the dynamics of spin states described by the Schr¨odinger equation for pure states and the von Neumann equation (as well as the GKSL equation) for mixed states in the form of quantum kinetic equations for probability distributions. We review an approach to the spin-state description by means of the probability distributions of dichotomic random variables. [ABSTRACT FROM AUTHOR]

Nitrosylation reaction mechanisms of the hydrolysates of NAMI‐A and hydrolysis reactions of ruthenium nitrosyl complexes were investigated in the triplet state and the singlet state. Activation free energies were calculated by combining the QM/MM(ABEEM) method with free energy perturbation theory, and the explicit solvent environment was simulated by an ABEEMσπ polarizable force field. Our results demonstrate that nitrosylation reactions of the hydrolysates of NAMI‐A occur in both the triplet and the singlet states. The Ru‐N‐O angle of the triplet ruthenium nitrosyl complexes is in the range of 132.0°–138.2°. However, all the ruthenium nitrosyl complexes at the singlet state show an almost linear Ru‐N‐O angle. The nitrosylation reaction happens prior to the hydrolysis reaction for the first‐step hydrolysates. The activation free energies of the nitrosylation reactions show that the H2O‐NO exchange reaction of [RuCl4(Im)(H2O)] in the singlet spin sate is the most likely one. Comparing with the activation free energies of the hydrolysis reactions of the ruthenium nitrosyl complexes, the results indicate that the rate of the DMSO–H2O exchange reaction of [RuCl3(NO)(Im)(DMSO)] is faster than that of [RuCl3(H2O)(Im)(DMSO)] in both the triplet spin state and the singlet spin state. © 2018 Wiley Periodicals, Inc. Ab initio method and ABEEM/MM‐FEP method have been combined to investigate reaction mechanism of the interactions of NO with NAMI‐A hydrolysates in both the triplet and singlet spin states. The combined QM/MM(ABEEM polarizable force field) method with MD‐FEP was employed to calculate the activation free energies. The rates of nitrosylation reactions are faster than those of further hydrolysis reactions for the first step hydrolysates of NAMI‐A. The activation free energies of the nitrosylation reactions show that the H2O‐NO exchange reaction of [RuCl4(Im)(H2O)] in the singlet spin sate is the most likely one. [ABSTRACT FROM AUTHOR]

Starting from their six‐coordinate iron(II) precursor complexes [L8RFe(MeCN)]2+, a series of iron(III) complexes of the known macrocyclic tetracarbene ligand L8H and its new octamethylated derivative L8Me, both providing four imidazol‐2‐yliden donors, were synthesized. Several five‐ and six‐coordinate iron(III) complexes with different axial ligands (Cl−, OTf−, MeCN) were structurally characterized by X‐ray diffraction and analyzed in detail with respect to their spin state variations, using a bouquet of spectroscopic methods (NMR, UV/Vis, EPR, and 57Fe Mößbauer). Depending on the axial ligands, either low‐spin (S=1/2) or intermediate‐spin (S=3/2) states were observed, whereas high‐spin (S=5/2) states were inaccessible because of the extremely strong in‐plane σ‐donor character of the macrocyclic tetracarbene ligands. These findings are reminiscent of the spin state patterns of topologically related ferric porphyrin complexes. The ring conformations and dynamics of the macrocyclic tetracarbene ligands in their iron(II), iron(III) and μ‐oxo diiron(III) complexes were also studied. Spin‐state patterns: Reminiscent of iron(III) porphyrinates and identified by characteristic spectroscopic signatures, ferric complexes of macrocyclic tetracarbenes were observed to adopt either low‐spin (S=1/2) or intermediate‐spin (S=3/2) states, depending on the number and field strength of axial ligands. Carbene ligation, however, rendered a high‐spin (S=5/2) state inaccessible. FeII/FeIII redox potentials and macrocycle ring dynamics were modulated by peripheral substituents at the equatorial tetracarbene scaffold. [ABSTRACT FROM AUTHOR]

In this work, we explore the applicability and limitations of the current third order density functional tight binding (DFTB3) formalism for treating transition metal ions using nickel as an example. To be consistent with recent parameterization of DFTB3 for copper, the parametrization for nickel is conducted in a spin‐polarized formulation and with orbital‐resolved Hubbard parameters and their charge derivatives. The performance of the current parameter set is evaluated based on structural and energetic properties of a set of nickel‐containing compounds that involve biologically relevant ligands. Qualitatively similar to findings in previous studies of copper complexes, the DFTB3 results are more reliable for nickel complexes with neutral ligands than for charged ligands; nevertheless, encouraging agreement is noted in comparison to the reference method, B3LYP/aug‐cc‐pVTZ, especially for structural properties, including cases that exhibit Jahn–Teller distortions; the structures also compare favorably to available X‐ray data in the Cambridge Crystallographic Database for a number of nickel‐containing compounds. As to limitations, we find it is necessary to use different d shell Hubbard charge derivatives for Ni(I) and Ni(II), due to the distinct electronic configurations for the nickel ion in the respective complexes, and substantial errors are observed for ligand binding energies, especially for charged ligands, d orbital splitting energies and splitting between singlet and triplet spin states for Ni(II) compounds. These observations highlight that future improvement in intra‐d correlation and ligand polarization is required to enable the application of the DFTB3 model to complex transition metal ions. © 2018 Wiley Periodicals, Inc. The density functional tight binding (DFTB) model parameterized for Nickel leads to reliable structural properties for Nickel‐containing compounds, including Jahn–Teller distortions, but less accurate ligand binding energies. More sophisticated treatment of the d‐d interactions is required to improve energetics, including the order of different spin states. [ABSTRACT FROM AUTHOR]

Square‐planar coordinate Ni2+ ions in oxides are exclusively limited to a low‐spin state (S=0) owing to extensive crystal field splitting. Layered oxychalcogenides A2NiIIO2Ag2Se2 (A=Sr, Ba) with the S=1 NiO2 square lattice are now reported. The structural analysis revealed that the Ni2+ ion is under‐bonded by a significant tensile strain from neighboring Ag2Se2 layers, leading to the reduction in crystal field splitting. Ba2NiO2Ag2Se2 exhibits a G‐type spin order at 130 K, indicating fairly strong in‐plane interactions. The high‐pressure synthesis employed here possibly assists the expansion of NiO2 square lattice by taking the advantage of the difference in compressibility in oxide and selenide layers. All in a spin: A high‐pressure reaction allows the synthesis of A2NiO2Ag2Se2 (A=Sr, Ba) with a square‐planar NiO2 sheet. These materials (and Cu/Mn analogues) have extremely long Ni−O (Cu/Mn−O) bonds owing to an extensive strain from AgSe layers, enabling an otherwise missing S=1 square‐planar state. The distinct compressibility between oxide and chalcogenide layers accounts for this phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: The spin state, specifically antibonding orbital (e g) occupancy, of transition‐metal ions is recognized as a descriptor for oxygen electrocatalysts with perovskite or spinel structures, and can be facilely adjusted by varying the valence states of transition metals. However, both perovskites and spinels show unsatisfactory performance even at the optimal spin states. In comparison, some oxides with a rock salt structure (e.g., NiIICoIIO2) exhibit higher activity than perovskites and spinels, nevertheless, the rock salt structure excludes valence changes of the transition metals, obstructing further e g optimization and performance enhancement. Herein, an innovative strategy is demonstrated to regulate the spin states of CoII in NiCoO2 via crystallinity manipulation, thus providing a new strategy for eg optimization. Remarkably, the catalyst (CNO‐8) with a moderate eg occupancy (≈1.2) achieves the best electrocatalytic activity, which is among the highest achieved by the state‐of‐the‐art electrocatalysts, namely, an overpotential of ≈269 mV at 10 mA cm−2 for oxygen evolution reaction and an onset potential of 935 mV for oxygen reduction reaction. As an efficient bifunctional catalyst for rechargeable Zn‐air batteries, CNO‐8 even outperforms the noble metal catalyst (Pt/C + RuO2), demonstrating high potential for practical applications in electrochemical energy conversion. [ABSTRACT FROM AUTHOR]

DFT/BP86 calculations have been carried out on a series of hypothetical binuclear compounds of general formula (L3M)2(C12N2H8) (M = Sc-Ni, L3 = (CO)3, (PH3)3 and Cp−, and C12N2H8 = phenazine ligand-denoted Phn). The various structures with syn and anti configurations have been investigated, in order to determine the phenazine’s coordination to first-row transition metals of various spin states with syn and anti conformations. The lowest energy structures depend on the nature of the metal, the spin state, and the molecular symmetry. This study has shown that the electronic communication between the metal centers depends on their oxidation state and the attached ligands. The tricarbonyl and the triphosphine ligands gave rise to comparable results in terms of stability order of isomers, metal-metal bond distances, and the coordination modes. Metal-metal multiple bonding has been evidenced for Sc, Ti, and V complexes to compensate the electronic deficiency. The Cr, Mn, Fe, Co, and Ni-rich metals prefer the anti conformation due to the enhancement of the metal valence electron count. The spin density values calculated for the triplet and quintet spin structures point out that the unpaired electrons are localized generally on the metal centers. The Wiberg bond indices are used to evaluate the metal-metal bonding. Furthermore, calculations using the BP86-D functional which take into account the attractive part of the van der Waals type interaction potential between atoms and molecules that are not directly connected to each other gave comparable results to those obtained by BP86 functional in terms of coordination modes, HOMO-LUMO gaps, metal-metal bond orders, and the stability order between isomers, but with slight deviation of M-C, M-N, and M-M bond distances not exceeding 3%. [ABSTRACT FROM AUTHOR]

Various aspects related to the use of DFT method for the study of magnetic, geometry and energetic properties of transition metal complexes with redox-active ligands are considered. Particular attention is given to the correct choice of model compounds and methodology of the calculations. [ABSTRACT FROM AUTHOR]

Abstract: The origin for the rotational barrier of organometallic versus inorganic sandwich complexes has remained enigmatic for the past decades. Here, we investigate in detail what causes the substantial barrier for titanodecaphosphacene through spin‐state consistent density functional theory. Orbital interactions are shown to be the determining factor. [ABSTRACT FROM AUTHOR]

We study the CHSH inequality for a system of two spin j particles, for generic j. The CHSH operator is constructed using a set of unitary, Hermitian operators { A 1 , A 2 , B 1 , B 2 }. The expectation value of the CHSH operator is analyzed for the singlet state | ψ s 〉. Being | ψ s 〉 an entangled state, a violation of the CHSH inequality compatible with Tsirelson's bound is found. Although the construction employed here differs from that of [1] , full agreement is recovered. • A novel operator construction to see entanglement in a system of two spins. • Violation of the CHSH inequality when the system is in the singlet state. • Differences between half-integer spin and integer spin regarding the Tsirelson's bound. [ABSTRACT FROM AUTHOR]

Evaluation of structure (experimental and theoretical) and biological activity of low-spin Fe(III) and high-spin Mn(II) complexes with hydrazone ligand. [Display omitted] Fe(III) and Mn(II) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (H L1 , (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In both complexes, the thiosemicarbazone ligand is coordinated in deprotonated form through the NNS donor set of atoms. However, while Fe(III) complex is in the doublet ground state with distorted octahedral geometry, the coordination environment around Mn(II) is distorted trigonal-prismatic, and the sextet state is found to be the ground state. DFT calculations were performed to rationalize spin state preferences, and continuous shape measure describes the deviation from ideal six-coordinated polyhedral geometries in the ground and excited states. Antimicrobial activity (against a panel of Gram-negative and Gram-positive bacteria, two yeast, and one fungal strain), brine shrimp assay, and DPPH radical scavenging activity of both complexes were evaluated, and these results relate to the electronic structure of the complexes. [ABSTRACT FROM AUTHOR]

Electron spin states play an important role in many chemical processes. Most spin-state studies require the application of a magnetic field. Recently it was found that the transport of electrons through chiral molecules also depends on their spin states and may also play a role in enantiorecognition. Electrochemistry is an important tool for studying spin-specific processes and enantioseparation of chiral molecules. A new device is presented, which serves as the working electrode in electrochemical cells and is capable of providing information on the correlation of spin selectivity and the electrochemical process. The device is based on the Hall effect and it eliminates the need to apply an external magnetic field. Spin-selective electron transfer through chiral molecules can be monitored and the relationship between the enantiorecognition process and the spin of electrons elucidated. [ABSTRACT FROM AUTHOR]

• The optoelectronic properties of La 2 CoO 4 and LaSrCoO 4 are investigated using the GGA, GGA + U, MBJ and MBJ + U approximations. • The experimental dielectric constants of La 2-x Sr x CoO 4 compounds were evaluated using DRS analyses and compared with GGA/MBJ + U approaches. • The existence of different valences and spin sates of Co ions significantly affect in the optoelectronic properties of La 2 CoO 4 and LaSrCoO 4 compounds. • MBJ and MBJ + U methods provide better description of band gap and optical properties of La 2 CoO 4 and LaSrCoO 4 compounds. • The dielectric coefficients estimated from GGA/MBJ + U methods are close agreement with the experimental results. In this research, the electronic structure and optical properties of La 2 CoO 4 and LaSrCoO 4 are such as dielectric function, refractive and extinction coefficients, the optical conductivity, reflectivity and absorption spectra were investigated using the generalized gradient (GGA and GGA + U) and modified Becke–Johnson (MBJ and MBJ + U) approximations. To compare the theoretical data with experimental results, both samples were synthesized using sol–gel method and their structure, morphology and optical properties were characterized using XRD analysis, FE-SEM imaging and UV–vis spectroscopy, respectively. It is found that the energy band gap of La 2 CoO 4 has been decreased with substitution of La3+ ions by Sr2+ in both the theoretical and experimental methods. According to our results, MBJ and MBJ + U approaches provide better description of band gap and optical properties of La 2 CoO 4 and LaSrCoO 4 compounds. This study can provide a reference for future research and helps to extend the properties of Ruddlesden-Popper materials into the optical applications. [ABSTRACT FROM AUTHOR]

Addition of 2,4,6-trinitrophenol (HTNP) to an ethene-bridged diiron(III) μ-oxo bisporphyrin ( 1) in CH2Cl2 initially leads to the formation of diiron(III) μ-hydroxo bisporphyrin ( 2⋅TNP) with a phenolate counterion that, after further addition of HTNP or dissolution in a nonpolar solvent, converts to a diiron(III) complex with axial phenoxide coordination ( 3⋅(TNP)2). The progress of the reaction from μ-oxo to μ-hydroxo to axially ligated complex has been monitored in solution by using 1H NMR spectroscopy because their signals appear in three different and distinct spectral regions. The X-ray structure of 2⋅TNP revealed that the nearly planar TNP counterion fits perfectly within the bisporphyrin cavity to form a strong hydrogen bond with the μ-hydroxo group, which thus stabilizes the two equivalent iron centers. In contrast, such counterions as I5, I3, BF4, SbF6, and PF6 are found to be tightly associated with one of the porphyrin rings and, therefore, stabilize two different spin states of iron in one molecule. A spectroscopic investigation of 2⋅TNP has revealed the presence of two equivalent iron centers with a high-spin state ( S=5/2) in the solid state that converts to intermediate spin ( S=3/2) in solution. An extensive computational study by using a range of DFT methods was performed on 2⋅TNP and 2+, and clearly supports the experimentally observed spin flip triggered by hydrogen-bonding interactions. The counterion is shown to perturb the spin-state ordering through, for example, hydrogen-bonding interactions, switched positions between counterion and axial ligand, ion-pair interactions, and charge polarization. The present investigation thus provides a clear rationalization of the unusual counterion-specific spin states observed in the μ-hydroxo bisporphyrins that have so far remained the most outstanding issue. [ABSTRACT FROM AUTHOR]

We show the star-product quantization procedure for spin-1/2 particles (qubits) employing the construction of a pair of operators - dequantizers and quantizers. We present an explicit description of all minimal systems of such dequantizers and quantizers and discuss their relation to the probability representation of spin states where the fair probability distribution is identified with the spin states. We give some examples and discuss the possibility of constructing a symplectic structure in the finite-dimensional phase space. [ABSTRACT FROM AUTHOR]

Solid oxide fuel cells are an important class of energy conversion devices in the search to replace fossil fuels. Their electrodes' materials mostly belong to the perovskite family, which in their versatile composition are numerous; here we focus on the perovskite LaCo xFe1− xO3 and examine its electronic structure for x ≤ 0.5 using density functional theory with a plane wave basis and pseudopotentials. The resulting lattice parameters show good agreement with experiment, and the Mulliken and Bader charges show that iron and cobalt mostly remain as Fe3+ and Co3+ throughout an increasing Co:Fe ratio. The charge and spin magnitudes of oxygen ions is determined by their local, cation neighbors with the largest charge and spin magnitudes found on oxygen ions sandwiched between two Fe ions. Density of states and partial density of states analyses reveal that increasing the ratio of Co to Fe in oxygen stoichiometric materials decreases their relative, semi-conducting nature toward insulating, by virtue of the decrease in the number of (conducting) O-Fe-O bonds and the increase in (insulating) O-Co-O bonds. The appearance of an intermediate spin state of Co and examination of its PDOS confirms the hypothesis that Co-O, d-p hybridization is a necessary factor for its occurrence. [ABSTRACT FROM AUTHOR]

A series of five-coordinate FeIII octaaryltetraphenylporphyrins [FeIII(por)(X)] (X = Cl, I, I3, ClO4, or SO3CF3) and their 1 e--oxidized complexes [FeIII(por ·)(X)(Y)] (X = Cl, I, ClO4, or SO3CF3; Y = SbCl6, I3, ClO4, or SO3CF3) have been synthesized and characterized. The electronic structures have been confirmed by using UV/Vis, IR, 1H NMR, EPR, and Mössbauer spectroscopy as well as signal-crystal X-ray diffraction studies. The neutral five-coordinate complexes exhibit spin states ranging from essentially pure high spin ( S = 5/2 with X = Cl), admixed intermediate spin ( S = 5/2, 3/2 with X = I) to an essentially pure intermediate spin ( S = 3/2 with X = I3, ClO4, and SO3CF3) depending upon the axial ligand field strength. The average Fe-Np length decreases with decreasing axial ligand strengths, Cl < I < ClO4 < I3 ≈ SO3CF3, which happens to be the order of increasing contributions of the intermediate-spin state to the complexes. DFT calculations demonstrate a dramatic change in the orbital energy levels upon changing the axial ligand strength. Upon 1 e- oxidation, the high-spin chloro complex forms the five-coordinate high-spin FeIII porphyrin π-cation radical, whereas the essentially pure intermediate perchlorato, triflato, triiodo iron(III) porphyrinates produce the corresponding six-coordinate high-spin iron(III) porphyrin π-cation radicals. The oxidation also induces larger separation between the up- and down-field shifted methylene resonances in the 1H NMR spectra owing to the presence of the π-cation radical. [ABSTRACT FROM AUTHOR]

Tomograms are obtained as probability distributions and are used to reconstruct a quantum state from experimentally measured values. We study the evolution of tomograms for different quantum systems, both finite and infinite dimensional. In realistic experimental conditions, quantum states are exposed to the ambient environment and hence subject to effects like decoherence and dissipation, which are dealt with here, consistently, using the formalism of open quantum systems. This is extremely relevant from the perspective of experimental implementation and issues related to state reconstruction in quantum computation and communication. These considerations are also expected to affect the quasiprobability distribution obtained from experimentally generated tomograms and nonclassicality observed from them. [ABSTRACT FROM AUTHOR]

Electrocoagulation (EC) in water treatment encounters several challenges, such as electrode fouling and passivation, especially when the effluent has a complex composition, such as produced water in the oil and gas industry. In this study, the effectiveness of applying an external magnetic field during EC with aluminum anodes (Al-EC) or mild steel anodes (Fe-EC) was investigated for the first time for the removal of inorganic contaminants (including silica, calcium, magnesium, and sulfide) from synthetic and field samples of produced waters. For Al-EC, the presence of a magnetic field perpendicular to the electric field was found to enhance the treatment performance and mitigate the fouling formation on the electrode surface. Chronoamperometric investigations indicated that the application of MF in Al-EC enhances the current density and reduces the time to form a fouling layer on the electrode. In contrast, with Fe-EC, the presence of the magnetic field increased the rate of fouling on the electrodes. Potentiodynamic and kinetic investigations indicate that the magnetic field improves mass transfer via Kelvin force and magnetohydrodynamic (MHD) effects with no impact on the type of kinetic model, while the change in the spin states of the accumulated species has a negligible impact on reducing the fouling. The resistivity of the accumulated fouling layer (δ R F) was found to reduce by around 23% due to a magnetic field of 0.158 T. Although increasing the strength of the applied MF increases the mass transfer, the effect is not linear. The results indicate that applying a magnetic field in Al-EC can be an effective method to mitigate fouling during water treatment. [Display omitted] • Fouling layers on electrodes impedes the performance of long-term water treatment. • External MF perpendicular to the electric field is effective for Al-EC but not Fe-EC. • MF enhances the treatment and mitigates fouling in Al-EC. • Kelvin force and MHD improves mass transfer more than the change in spin states. • The resistivity of the accumulated fouling layer was reduced by 23% with 0.158 T. [ABSTRACT FROM AUTHOR]

The structures of nine iron complexes that show a diversity of experimentally observed spin ground states were optimized and analyzed using the Density Functional Theory (DFT). An extensive validation study of the new S12g functional was performed, with a discussion concerning the influence of the environment, geometry and its overall performance based on a comparison with the well-proven OPBE functional. The OPBE and S12g functionals gave the correct spin ground state for all investigated iron complexes. Since S12g performs remarkably well, it could be considered a reliable tool for studying the energetics of the spin state in complicated transition metal systems. [ABSTRACT FROM AUTHOR]

Dirac equation for electrons in a potential created by quantum well is solved and the three sets of the eigen-functions are obtained. In each set the wavefunction is at the same time the eigen-function of one of the three spin operators, which do not commute with each other, but do commute with the Dirac Hamiltonian. This means that the eigen-functions of Dirac equation describe three independent spin eigen-states. The energy spectrum of electrons confined by the rectangular quantum well is calculated for each of these spin states at the values of energies relevant for solid state physics. It is shown that the standard Rashba spin splitting takes place in one of such states only. In another one, 2D electron subbands remain spin degenerate, and for the third one the spin splitting is anisotropic for different directions of 2D wave vector. [ABSTRACT FROM AUTHOR]

Full geometry optimization using the BP86 and B3LYP methods has been carried out for all of the low-energy isomers of half-sandwich L3M(Tphn) (Tphn = triphenylene, M = Ti-Ni, and L3 = (CO)3, Cp-) and sandwich M(Tphn)2 (Tphn = triphenylene and M = Ti, Cr, Fe, Ni) structures. Depending on the electron richness of the molecule and the nature of the metal, a complete rationalization of the bonding in triphenylene complexes has been provided. The triphenylene adopts various hapticities from η2 to η6, some of them involving full or partial coordination of the C6 ring and shown to be quite flexible with respect to the ground spin state. The triphenylene behavior remains dependent on the electron-withdrawing and electron-donor properties of the (CO)3M and CpM fragments, respectively. For the sandwich complexes, both triphenylene ligands prefer to behave differently depending on the coordination mode to satisfy the metal electron demand. [ABSTRACT FROM AUTHOR]

Development of efficient and affordable electrocatalysts in neutral solutions is paramount importance for the renewable energy. Herein, we report that the oxygen evolution reaction (OER) performance of Co3S4 under neutral conditions can be enhanced by exposed octahedral planes and self-adapted spin states in atomically thin nanosheets. A HAADF image clearly confirmed that the active octahedra with Jahn-Teller distortions were exposed exclusively. Most importantly, in the atomically thin nanosheets, the spin states of Co3+ in the octahedral self-adapt from low-spin to high-spin states. As a result, the synergistic effect endow the Co3S4 nanosheets with superior OER performance, with exceptional low onset overpotentials of circa 0.31 V in neutral solutions, which is state-of-the-art among inorganic non-noble metal compounds. [ABSTRACT FROM AUTHOR]

Rare earth elements (REs) consist of a very important group in the periodic table that is vital to manymodern technologies. The mining process, however, is extremely damaging to the environment, making them low yield and very expensive. Therefore, mimicking the properties of REs in a superatom framework is especially valuable but at the same time, technically challenging and requiring advanced concepts about manipulating properties of atom/molecular complexes. Herein, by using photoelectron imaging spectroscopy, we provide original idea and direct experimental evidence that chosen boron-doped clusters could mimic the magnetic characteristics of REs. Specifically, the neutral LaB and NdB clusters are found to have similar unpaired electrons and magnetic moments as their isovalent REs (namely Nd and Eu, respectively), opening up the great possibility in accomplishing rare earth mimicry. Extension of the superatom concept into the rare earth group not only further shows the power and advance of this concept but also, will stimulate more efforts to explore new superatomic clusters to mimic the chemistry of these heavy atoms, which will be of great importance in designing novel building blocks in the application of cluster-assembled nanomaterials. Additionally, based on these experimental findings, a novel "magic boro" counting rule is proposed to estimate the numbers of unpaired electrons in diatomic LnB clusters. [ABSTRACT FROM AUTHOR]