3d Transition Elements Research Articles

Prediction by DFT and Docking Calculations of a Series of Hypothetical 3d Transition Element Isostructural Complexes [M(hfac)2(TTF)2]: A Comparative Study

AbstractThe study aims to predict and compare the structural, electronic, conductivity, and biological properties of a series of 3d transition element complexes with those of the previously studied isostructural copper complex [Cu(hfac)2(TTF)2][PF6]2 (TTF: tetrathiafulvalene, hfac: hexafluoroacetylacetonate). Because transition metals hold open electronic shells, all possible spin states for all divalent compounds have to be considered in order to determine the most stable configurations. These configurations are those corresponding to the highest spin state (5 for Mn, 4 for Fe, 3 for Co, 2 for Ni, 1 for Cu, and 0 for Zn). However, the configurations with the smallest gap are Mn(3) and Co(1), suggesting that these are the most conductive complexes. A significant metal–ligand charge transfer is observed for both Mn and Co complexes. Antifungal (CYP121 (PDB: 2IJ7) and CYP51 (PDB: 1EA1)) and antibacterial (Escherichia coli (PDB: 1KZN)) properties of the compounds studied were evaluated by molecular docking; the results obtained reveal that the following complexes show significant activity: Zn(hfac)2(TTF)2] [PF6]2 (−8.9 kcal/mol), Ni(hfac)2(TTF)2] [PF6]2 (−7.8 kcal/mol), and Cu(hfac)2(TTF)2] [PF6]2 (−8.2 kcal/mol).

Single‐Atom 3d Transition Metals on SnO2 as Model Cell for Conversion Mechanism: Revealing Thermodynamic Catalytic Effects on Enhanced Na Storage of Heterostructures

AbstractSince the discovery in 2000, conversion‐type materials have emerged as a promising negative‐electrode candidate for next‐generation batteries with high capacity and tunable voltage, limited by low reversibility and severe voltage hysteresis. Heterogeneous construction stands out as a cost‐effective and efficient approach to reducing reaction barriers and enhancing energy density. However, the second term introduced by conventional heterostructure inevitably complicates the electrochemical analysis and poses great challenges to harvesting systematic insights and theoretical guidance. A model cell is designed and established herein for the conversion reactions between Na and TMSA−SnO2, where TMSA−SnO2 represents single atom modification of eight different 3d transition elements (V, Cr, Mn, Fe, Co, Ni, Cu or Zn). Such a model unit fundamentally eliminates the interference from the second phase and thus enables independent exploration of activation manifestations of the heterogeneous architecture. For the first time, a thermodynamically dependent catalytic effect is proposed and verified through statistical data analysis. The mechanism behind the unveiled catalytic effect is further elucidated by which the active d orbitals of transition metals weaken the surface covalent bonds and lower the reaction barriers. This research provides both theoretical insights and practical demonstrations of the advanced heterogeneous electrodes.

Single-Atom 3d Transition Metals on SnO2 as Model Cell for Conversion Mechanism: Revealing Thermodynamic Catalytic Effects on Enhanced Na Storage of Heterostructures.

Since the discovery in 2000, conversion-type materials have emerged as a promising negative-electrode candidate for next-generation batteries with high capacity and tunable voltage, limited by low reversibility and severe voltage hysteresis. Heterogeneous construction stands out as a cost-effective and efficient approach to reducing reaction barriers and enhancing energy density. However, the second term introduced by conventional heterostructure inevitably complicates the electrochemical analysis and poses great challenges to harvesting systematic insights and theoretical guidance. A model cell is designed and established herein for the conversion reactions between Na and TMSA-SnO2, where TMSA-SnO2 represents single atom modification of eight different 3d transition elements (V, Cr, Mn, Fe, Co, Ni, Cu or Zn). Such a model unit fundamentally eliminates the interference from the second phase and thus enables independent exploration of activation manifestations of the heterogeneous architecture. For the first time, a thermodynamically dependent catalytic effect is proposed and verified through statistical data analysis. The mechanism behind the unveiled catalytic effect is further elucidated by which the active d orbitals of transition metals weaken the surface covalent bonds and lower the reaction barriers. This research provides both theoretical insights and practical demonstrations of the advanced heterogeneous electrodes.

Balance between FeIV-NiIV synergy and Lattice Oxygen Contribution for Accelerating Water Oxidation.

Hydrogen obtained from electrochemical water splitting is the most promising clean energy carrier, which is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Thus, the development of an efficient OER electrocatalyst using nonprecious 3d transition elements is desirable. Multielement synergistic effect and lattice oxygen oxidation are two well-known mechanisms to enhance the OER activity of catalysts. The latter is generally related to the high valence state of 3d transition elements leading to structural destabilization under the OER condition. We have found that Al doping in nanosheet Ni-Fe hydroxide exhibits 2-fold advantage: (1) a strong enhanced OER activity from 277 mV to 238 mV at 10 mA cm-2 as the Ni valence state increases from Ni3.58+ to Ni3.79+ observed from in situ X-ray absorption spectra. (2) Operational stability is strengthened, while weakness is expected since the increased NiIV content with 3d8L2 (L denotes O 2p hole) would lead to structural instability. This contradiction is attributed to a reduced lattice oxygen contribution to the OER upon Al doping, as verified through in situ Raman spectroscopy, while the enhanced OER activity is interpreted as an enormous gain in exchange energy of FeIV-NiIV, facilitated by their intersite hopping. This study reveals a mechanism of Fe-Ni synergy effect to enhance OER activity and simultaneously to strengthen operational stability by suppressing the contribution of lattice oxygen.

Unlocking the role of 3d electrons on ferromagnetism and spin-dependent transport properties in K2GeNiX6 (X=Br, I) for spintronics and thermoelectric applications

In our quest for novel materials, we undertake a rigorous ab-initio investigation to unravel the structural stability, electronic profile, and thermoelectric properties of halide double perovskites K2GeNiX6 (X = Br, I). Our exploration commences with a meticulous evaluation of structural and thermodynamic stability, utilizing diverse metrics for comprehensive scrutiny. Subsequently, we optimize the structures using the GGA-PBE potential at the behest of the Birch-Murnaghan equation of state to identify energetically favoured configurations. The ferromagnetic phase emerges as the ground state, supported by positive Curie-Weiss constant values of 120 K for K2GeNiBr6 and 100 K for K2GeNiI6, respectively. To elucidate the precise determination of the electronic structure, we utilized the highly sophisticated TB-mBJ potential, unveiling a ferromagnetic semiconductor nature for both materials. The band structure exhibits a pronounced asymmetry, indicating the presence of spin-magnetic moments. Notably, K2GeNiBr6 and K2GeNiI6 display substantial magnetic moments of 2 μB each, primarily associated with the 3d-transition element Ni2+. Additionally, we determine the Curie temperature, disclosing substantial values of 510 K and 430 K for K2GeNiBr6 and K2GeNiI6, respectively. Our investigation extends to encompass thermodynamic parameters, considering vibrational contributions to internal energy, Helmholtz free energy, and other factors that collectively serve as indicators of thermal stability. Finally, we examine the impact of both chemical potential and temperature variations on key thermoelectric parameters, specifically the Seebeck coefficient, electrical conductivity, and the figure of merit (zT). The findings unveil a significant thermoelectric figure of merit (zT) with values of 1.00 and 0.99 for K2GeNiBr6 and K2GeNiI6, respectively. The overall comprehensive analysis underscores the substantial potential of these tailored materials in applications pertaining to semiconductor spintronics and thermoelectric devices.

Exploring the multifaceted properties: electronic, magnetic, Curie temperature, elastic, thermal, and thermoelectric characteristics of gadolinium-filled PtSb3 skutterudite.

The investigation of binary and filled skutterudite structures, particularly PtSb3 and GdPt4Sb12, has gained significant attention, becoming a focal point in scientific research. This comprehensive report delves into the intrinsic characteristics of these structures using Density Functional Theory (DFT). Initially, we assess the structural stability of PtSb3 and GdPt4Sb12 by examining their total ground state energy and cohesive energy, employing the Brich Murnaghan equation of state to determine stability in various configurations. Further insights are gained by exploring second-order elastic constants (SOEC's) to extend our understanding of structural stability. The electronic structures are then meticulously defined through a quantum mechanical treatment, employing a combination of two distinct spin-polarized approximation schemes: Perdew-Burke-Ernzerhof Generalised Gradient Approximation (PBE-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ). The resulting band structures reveal a symmetry in electronic behavior, showcasing spin-magnetic moments of 3 μB and 7.58 μB per formula unit, with the primary contributions emanating from the Pt 3d and Pt4+ 3d-transition elements. To gauge thermal stability, we evaluate the phonon-dependent Grüneisen parameter (γ) across specific temperature ranges. The study extends to exploring transport properties as a function of chemical potential (μ - EF) at various temperatures. The findings suggest that these designed materials hold substantial potential for diverse applications, particularly in conventional spin-based and thermoelectric technologies. The comprehensive insights obtained through this investigation pave the way for a deeper understanding and broader implications in various technological domains.

Prediction of Van Hove singularity systems in ternary borides

A computational search for stable structures among both α and β phases of ternary ATB4 borides (A = Mg, Ca, Sr, Ba, Al, Ga, and Zn, T is 3d or 4d transition elements) has been performed. We found that α-ATB4 compounds with A = Mg, Ca, Al, and T = V, Cr, Mn, Fe, Ni, and Co form a family of structurally stable or almost stable materials. These systems are metallic in non-magnetic states and characterized by the formation of the localized molecular-like state of 3d transition metal atom dimers, which leads to the appearance of numerous Van Hove singularities in the electronic spectrum. The closeness of such singularities to the Fermi level can be easily tuned by electron doping. For the atoms in the middle of the 3d row (Cr, Mn, and Fe), these singularities led to magnetic instabilities and magnetic ground states with a weakly metallic or semiconducting nature. Such states appear as non-trivial coexistence of the different spin ladders formed by magnetic dimers of 3d elements. These magnetic states can be characterized as an analog of the spin glass state. Experimental attempts to produce MgFeB4 and associated challenges are discussed, and promising directions for further synthetic studies are formulated.

Atomic data and expansion opacity calculations in two representative 4d transition elements, niobium and silver, of interest for kilonovae studies

Aims. Neutron star (NS) mergers are thought to be a source of heavy trans-iron element production. The latter can be detected in the spectra of the ejected materials, from which bright electromagnetic radiation is emitted. This latter is due to the radioactive decay of the produced heavy r-process nuclei and is known as kilonova. Because of their complex atomic structures – characterized by configurations involving unfilled nd or nf subshells – the heavy elements of the kilonova ejecta often give rise to numerous absorption lines generating significant opacities. The determination of the latter, which are of paramount importance for the analysis of kilonova light curves, requires knowledge of the radiative parameters of the spectral lines belonging to the ions expected to be present in the kilonova ejecta. The aim of the present work is to provide new atomic opacity data for two representative 4d elements, niobium (Nb) and silver (Ag), in their first four charge states, namely for Nb I–IV and Ag I–IV. Methods. Large-scale calculations based on the pseudo-relativistic Hartree-Fock (HFR) method were performed to obtain the atomic structure and radiative parameters while the expansion formalism was used to estimate the opacities. Results. Wavelengths and oscillator strengths were computed for several million spectral lines in Nb I–IV and Ag I–IV ions. The reliability of these parameters was estimated by comparison with the few previously published experimental and theoretical results. The newly obtained atomic data were then used to calculate expansion opacities for typical kilonova conditions expected one day after NS merger, a density of ρ = 10−13 g cm−3, and temperatures ranging from T = 5000 K to T =15 000 K.

A Study on Radiation Shielding Abilities of Some Compounds of 3d Transition Elements by Using Phy-X/PSD Code

In the present study, it was aimed to calculate the radiation-matter interaction parameters of some compounds of 3d transition elements. The radiation attenuation parameters, which are important to have knowledge about the radiation shielding potentials, were calculated by using Phy-X/PSD code in the energy range of 0.01-15 MeV. The calculated mass attenuation coefficient and effective atomic number results were compared with the experimental data which were measured at 19.63 and 22.10 keV previously and, a good agreement was achieved. In order to evaluate the shielding properties of the compounds, we also compared the mass attenuation coefficients of the compounds with ordinary concrete, steel-scrap, ilmenite-limonite and basalt-magnetite, which are widely used as radiation protective materials. According to the obtained results, it is concluded that the studied compounds have radiation shielding potentials.

Compositive role of refractory element Mo in improving strength and ductility of face-centered-cubic complex concentrated alloys

Complex concentrated alloys (CCAs) with a face-centered-cubic (FCC) structure exhibit remarkable mechanical properties, introducing the expansion of compositional space in alloy design for structural materials. The formation of a single solid-solution phase is enabled by configuring various 3d-transition elements, while doping other elements even of a small portion generally leads to the formation of brittle intermetallic compounds. Herein, we demonstrate through a systematic investigation of single FCC (CoNi)100-xMox alloys that a wide range of refractory element Mo can simultaneously improve the strength and ductility while sustaining the solid-solution structure. The addition of Mo with a larger atomic size than those of 3d-transition elements introduces severe lattice distortion in the FCC lattice and causes grain-boundary segregation enriched by Mo atoms. In addition, increasing Mo content effectively reduces the stacking fault energy (SFE). The increased lattice distortion with Mo content enhances the solid-solution strengthening of the alloys. Besides, along with reduced SFE and stabilization of the dislocation emission site by grain-boundary segregation, this elevated solid-solution strengthening increases grain-boundary strengthening, reaching a yield strength of ∼1 GPa. Moreover, the reduction of SFE with increasing Mo results in the transition of dislocation substructures and the refinement of deformation twins, allowing for enhanced strain-hardening capability and thus ∼1.3 GPa tensile strength and ∼50% ductility. Such compositive and synergetic effects of refractory element Mo enable the CCAs with a single FCC solid solution to overcome the strength and ductility trade-off.

First-principles calculations to investigate structural, electronic, phonon, magnetic and thermal properties of stable halide perovskite semiconductors Cs2GeMnI6 and Cs2GeNiI6

Since, the systematic and extensive study on halide double perovskite’s (HDP’s) have triggered a considerable interest, thus became a new thrust to the scientific research. In this organised report, we present a new promising halide double perovskite structures Cs2GeMnI6 and Cs2GeNiI6 to understand, more in-depth their intrinsic characteristics by means of Density Functional Theory (DFT). Initially, we reported the structural stability of both these crystal structures by evaluating their total ground state energy in stable configuration and cohesive energy at the behest of Brich Murnaghan equation of state. Afterwards, the structural stability is moreover extended to see their corresponding tolerance factor (τ) values and second order elastic constants (SOEC’s). Subsequently, the density functional perturbation theory (DFPT) has been inducted to predict the dynamical context of these ordered systems. Later on, the quantum mechanical treatment of defining their electronic structures by the calibration of mix of two distinct spin-polarised approximation schemes like Perdew-Burke-Ernzerhof Generalised gradient approximation (PBE-GGA) followed by Tran-Blaha modified Becke-Johnson (TB-mBJ). Meanwhile, the unsymmetrical behaviour of electronic structures from their resulting band structures demonstrates the occurrence of spin-magnetic moment of 5 µB and 2 µB/formula unit respectively having the maximum contribution solely coming from the Mn+2 and Ni2+ 3d-transition elements. The evaluation of phonon dependent Grüneisen parameter (γ) defines the possible thermal stability against specific temperature regimes. And finally transport properties as a function of chemical potential (µ-EF) at distinct temperatures has been keenly explored. Therefore, the overall tendency of these designed materials can be envisaged to descript vast implications in various extending applications for conventional spin-based and thermoelectric technologies.

Alloying effects on site preference, mechanical properties, and deformation behavior of L12 Co–Ti-based alloys

Alloying plays an important role in controlling the phase stability, mechanical properties, and deformation behavior of ordered intermetallic compounds. In this study, the effects of 3d, 4d, and 5d transition elements on site preference, elastic properties, ideal shear strength, and planar fault energies of L12 Co–Ti-based alloys were systematically investigated by using first-principles calculations. The calculated transfer energy and formation enthalpy indicate that Sc, V, Cr, Y, Zr, Nb, Mo, W, Hf, Ta, and W tend to occupy the Ti site, which reduce the structural stability of L12-Co3Ti. The elastic moduli and ideal shear strength of L12-Co3(Ti,M) increase with average electron density. The electron localization function (ELF) analysis reveals that the Co–M bonds have a stronger covalent character than the Co–Ti bond, which plays an important role in the strengthening of the alloys. The ratio of superlattice intrinsic stacking fault (SISF) to anti-phase boundary (APB) energy of L12-Co3(Ti,M) decreases with increasing atomic number of alloying elements in each period in the range of studied elements, which tends to change the deformation mode from the APB-favored to SISF-favored ones. The APB anisotropy ratio of L12-Co3(Ti,M) decreases with increasing atomic number of alloying elements in each period, which enhances the yield strength anomaly. This study not only sheds insight into the fundamental understanding of phase stability and mechanical behavior of multicomponent L12 compounds, but also provides useful guidelines for designing novel L12-stregnthened Co-based superalloys with superior mechanical properties.

The LSPIM-based numerical manifold method (NMM) for modeling transition elements

In many structural applications, the transition region, where the solids connect to the shells, is of considerable interest. Due to the complex behavior of this area, accurate modeling is necessary in practical problems. A numerical manifold method (NMM) based on the least square point interpolation method (LSPIM) free from linear dependence, is proposed to simulate this region. First, the basic formulations of local approximation based on LSPIM and the method to construct composite shape function are briefly introduced. This new composite shape function possesses the Kronecker-delta, inter-element compatibility, and higher-order completeness properties. Then, the formulations of the hexahedral element, 3D shell and 3D transition elements are derived based on the proposed method. Several examples are carried out to validate the accuracy and robustness of the suggested method for simulation of transition regions.

Design and characterization of a novel MgAlZnCuMn low melting point light weight high entropy alloy (LMLW-HEA)

Development of high-entropy alloys (HEAs) is one of the remarkable advancements in the progress of new materials. In recent years, continuous efforts have been made to design light weight high-entropy alloys (LWHEAs) with suitable microstructure and superior properties. This paper reports the preliminary results of a study aimed at design and development of a new low melting point LWHEA (LMLW-HEA) based on AlMgZnCuMn alloy system without excessive intermetallic compounds formation. In this research, first, the initial chemical composition of the alloy was designed according to thermodynamic parameters, and then the alloy was melted in a resistance electric furnace. Since the thermodynamic indicators have been defined based on alloys containing 3d transition elements, formation of binary intermetallic compounds was predicted with the help of Midema model. To investigate the effects of cooling rate and heat treatment on the structure of the designed alloy, the molten alloy was poured into two different molds made of silica sand and steel, and both as cast samples were also heat treated. Microstructural features, mechanical properties and thermal stability of the samples were then examined. Density of the samples was measured to be less than 3.4 gr/cm3 which was very close to the theoretical density of the alloy. Structures of all the samples were complex and multi-phase and contained intermetallic (ordered solid solution) binary and ternary compounds including Mg7Zn3, MgZn2, Cu2Mg, Al2Cu, Mg32 (Al, Zn)49, Mg32Cu7Al47, Al25Mg37.5Zn37.5, and CuMgZn phases. The designed alloy was brittle under all the processing conditions. Compressive strength of the alloy reached to about 95 MPa, and its hardness was in the range of 110–120 HV. Oxidation resistance of the alloy was evaluated at a temperature about 30 °C below its solidus temperature and no weight change was observed in the sample after 14 h. It is suggested that the designed alloy is a suitable candidate for high temperature applications not involving impact or cyclic loading.

Synthesis, Structural and Electrochemical Performance of Tetragonal Spinel MgMn2O4 Cathode Materials Promoted by 3d and 4d Transition Element

Synthesis, Structural and Electrochemical Performance of Tetragonal Spinel MgMn2O4 Cathode Materials Promoted by 3d and 4d Transition Element

Local Coordination Environment of 3d and 4d Transition Metal Ions in LiCl-KCl Eutectic Mixture.

In this study, the structure and coordination environment of two 3d transition elements (Ni and Cr) is investigated in a molten chloride salt system. Electronic absorption spectroscopy was employed to elucidate their coordination environment in 3LiCl-2KCl eutectic salt, as a function of temperature. Density functional theory (DFT) modeling was used to determine the coordination environment of the transition metal species in the eutectic composition as well as the optical spectra computationally. The Ni2+and Cr3+ exist in a tetrahedral and octahedral coordination environment, respectively, in eutectic salt. The spectra thus obtained were compared with the experimental data; a reasonable qualitative agreement was obtained between experimental and computational Ni2+ and Cr3+spectra, and the coordination of both elements in the eutectic composition were in excellent agreement with the experimentally determined results. Computational results were also obtained for two 4d elements, Mo3+ and Nb3+, with both quantum molecular dynamics (QMD) and hybrid functional optical spectra indicating octahedral coordination.

Structural, Thermal and Physical Properties of the Calcium Borovanadate Glasses Belonging to the 40CaO-(60-x)B2O3-xV2O5 System

The calcium borovanadate glasses within the system 40CaO-(60-x)B2O3 -xV2O5 with x= 0, 5, 10, 15, 20, 30, 40 mol% was studied. The glass samples were elaborated via melting, followed by quenching. Its structural, thermal, and physical properties were explored. Powder X-ray diffraction was used to demonstrate that the developed glasses were amorphous. The influence of vanadium, a 3d transition element, on physical characteristics such as density and molar volume was investigated. The variation of density and molar volume has been discussed in terms of the structural changes in the vitreous matrix with adding the V2O5. Infrared (FTIR) and Raman spectroscopies were done to check the group constitution of the glass. This analysis shows that the vitreous materials are mainly established from BO4 and BO3 units with four and five coordinated vanadium in all glasses containing V2O5, confirmed with the density results. Moreover, it is found from the infrared spectra the existence of diborovanadate [B2V2O9]2- in glass samples with composition x =15, 20, 30, 40.

Спонтанный спиновый магнетизм донорных электронов проводимости гибридизированных состояний кристалла, образованных системой примесных атомов 3d-элементов низкой концентрации (<1 at.%)

The given work is devoted to the experimental proof of existing the spontaneous spin polarization of the donor electron system of 3d-transition element impurity atoms of low concentration (<1 at.%) in a mercury selenide crystal. For this purpose there have been measured the dependences of the magnetization on the magnetic field strength. As a result of the analysis of the obtained dependences, there were extracted the impurity contributions, which are described by the magnetization curves typical of the ferromagnets, and by the magnetic parameters conforming to the spontaneous magnetism of the systems under study, which are unambiguously related to the donor conduction electrons of the outer d-shells of impurity atoms. By its nature, according to the developed theoretical concepts, the spontaneous spin polarization manifests itself in exchange interaction, taking place in hybridizing the electronic states of the impurity atom and the conduction band ones of the crystal.

Spontaneous spin magnetism of donor conduction electrons of hybridized states of a crystal formed by a system of 3d-elements impurity atoms of low concentration (<1 at.%)

The given work is devoted to the experimental proof of existing the spontaneous spin polarization of the donor electron system of 3d-transition element impurity atoms of low concentration (<1 at.%) in a mercury selenide crystal. For this purpose there have been measured the dependences of the magnetization on the magnetic field strength at low temperatures (T=5 K). As a result of the analysis of the obtained dependences, there were extracted the impurity contributions, which are described by the magnetization curves typical of the ferromagnets, and by the magnetic parameters conforming to the spontaneous magnetism of the systems under study, which are unambiguously related to the donor conduction electrons of the outer d-shells of impurity atoms. By its nature, according to the developed theoretical concepts, the spontaneous spin polarization manifests itself in exchange interaction, taking place in hybridizing the electronic states of the impurity atom and the conduction band ones of the crystal. Keywords: 3d-impurities of the low concentration, gapless semiconductors, hybridized electronic states, spontaneous spin polarization, low-temperature ferromagnetism

Luminescence in the system Al2O3-B2O3

Three compounds in the system Al2O3-B2O3, viz. Al4B2O9, Al5BO9 and Al18B4O33 were successfully prepared by facile combustion synthesis. Activation by 3d transition element Cr3+ and 4f lanthanide Ce3+ was attempted. Characteristic luminescence in form of narrow R lines of Cr3+ was observed in Al5BO9 and Al18B4O33. Interaction of Cr3+ with the surrounding was represented by the Racah parameters. Broad band emission of Ce3+ arising from allowed d-f transitions in near ultraviolet (nUV) region in all 3 compounds is reported for the first time.