Electronic and magnetic properties of all 3d transition‐metal‐doped ZnO monolayers

Stable geometries, electronic structures, and magnetic properties of the ZnO monolayer doped with 3d transition‐metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) atoms substituting the cation Zn have been investigated using first‐principles pseudopotential plane wave method within density functional theory (DFT). It is found that these nine atomic species can be effectively doped in the ZnO monolayer with formation energies ranging from ?6.319 to ?0.132 eV. Furthermore, electronic structures and magnetic properties of ZnO monolayer can be modified by such doping. The results show that the doping of Cr, Mn, Fe, Co, Ni, and Cu atoms can induce magnetization, while no magnetism is observed when Sc, Ti, and V atoms are doped into the ZnO monolayer. The magnetic moment is mainly due to the strong p–d mixing of O and TM (Cr, Mn, Fe, Co, Ni, and Cu) orbitals. These results are potentially useful for spintronic applications and the development of magnetic nanostructures. © 2013 Wiley Periodicals, Inc.     

Structural,electronic, and magnetic properties of 3d transition metal doped GaN nanosheet: A first‐principles study

We have performed the first‐principles calculations on the structural, electronic, and magnetic properties of 3d transition‐metal? (Cr, Mn, Fe, Co, and Ni) atoms doped 2D GaN nanosheet. The results show that 3d TM atom substituting one Ga leads to a structural reconstruction around the 3d TM impurity compared to the pristine GaN nanosheet. The doping of TM atom can induce magnetic moments, which are mainly located on the 3d TM atom and its nearest‐neighbor N atoms. It is found that Mn‐ and Ni‐doped GaN nanosheet with 100% spin polarization characters seem to be good candidates for spintronic applications. When two Ga atoms are substituted by two TM dopants, the ferromagnetic (FM) ordering becomes energetically more favorable for Cr‐, Mn‐, and Ni‐doped GaN nanosheet with different distances of two TM atoms. On the contrary, the antiferromagnetic (AFM) ordering is energetically more favorable for Fe‐doped GaN nanosheet. In addition, our GGA + U calculations show the similar results with GGA calculations. © 2016 Wiley Periodicals, Inc.     

Giant Magnetoresistance in the Half‐Metallic Double‐Perovskite Ferrimagnet Mn2FeReO6

The first transition‐metal‐only double perovskite compound, Mn²⁺₂Fe³⁺Re⁵⁺O₆, with 17 unpaired d electrons displays ferrimagnetic ordering up to 520 K and a giant positive magnetoresistance of up to 220 % at 5 K and 8 T. These properties result from the ferrimagnetically coupled Fe and Re sublattice and are affected by a two‐to‐one magnetic‐structure transition of the Mn sublattice when a magnetic field is applied. Theoretical calculations indicate that the half‐metallic state can be mainly attributed to the spin polarization of the Fe and Re sites.     

Band‐Gap Control of Zinc Sulfide: Towards an Efficient Visible‐Light‐Sensitive Photocatalyst

The electronic properties of transition‐metal‐doped zinc sulfide (ZnS) have been investigated by using first‐principles calculations. Transition‐metal doping can allow electronic transitions at energies corresponding to visible‐light wavelengths, thus potentially resulting in increased photocatalytic efficiency under sunlight. In particular, our calculations show that transition‐metal atoms that produce little lattice strain, such as Co, Ni, Mn, and Fe, can be readily incorporated in ZnS. Due to their low formation energies and appropriate band energies, we predict that Ni‐ and Co‐doped ZnS will be promising materials for photocatalytic hydrogen production.     

Magnetic ordering and metal‐atom site preference in tetragonal CrMnAs: Electronic correlation effects

The electronic and magnetic structures of tetragonal, Cu₂Sb‐type CrMnAs were examined using density functional theory. To obtain reasonable agreement with reported atomic and low‐temperature magnetic ordering in this compound, the intra‐atomic electron–electron correlation in term of Hubbard U on Mn atoms are necessary. Using GGA + U, calculations identify four low‐energy antiferromagnetically ordered structures, all of which adopt a magnetic unit cell that contains the same direct Cr Cr and Cr Mn magnetic interaction, as well as the same indirect Mn⋅⋅⋅Mn magnetic interaction across the Cr planes. One of these low‐energy configurations corresponds to the reported case. Effective exchange parameters for metal–metal contacts obtained from SPRKKR calculations indicate both direct and indirect exchange couplings play important roles in tetragonal CrMnAs. © 2018 Wiley Periodicals, Inc.     

DTPA-BpABA与锰配合物的结构表征和弛豫研究

X-ray single crystal analysis of a new paramagnetic manganese（Ⅱ） complex with DTPA-BpABA （a DTPAbisamide derivative）, Mn（DTPA-BpABA）·4H2O, shows that four oxygen atoms and three nitrogen atoms from the ligand coordinate to Mn（Ⅱ） cation, forming a seven-coordinate distorted pentagonal bipyramid polyhedron. In the crystal, the carboxyl groups and the nitrogen atoms extensively form hydrogen bonds with the lattice water molecules, building a 3D-network. The relaxometric study indicates that the R1 value of the paramagnetic manganese（Ⅱ）complex is 5.12 mmol·L·s^-1. The higher R1 value means that this complex may find an application in magnetic resonance imaging （MRI） technique.     

Theoretical study of the geometric and electronic structure of neutral and anionic doped silver clusters, Ag5X with X = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni

Density functional theory (DFT) has been applied to investigate the low-lying electronic states of neutral and anionic transition metal doped silver clusters Ag₅X^0,− with X = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni using the B3LYP functional with the Stuttgart SDD basis sets. The structural features, frontier orbital energy gaps (HOMO and LUMO), vertical detachment energies, and vertical and adiabatic electronic affinities are evaluated. For all doped silver clusters, both in neutral and anionic states, two-dimensional and three-dimensional low-energy isomers are found to coexist. For neutral clusters, dopant Sc, Ti, V, and Mn atoms largely decrease the frontier orbital energy gaps, while they are markedly increased by Sc and Fe atoms in the anionic clusters. A completely quenched dopant magnetic moment is found in Ag₅Sc, while high spin magnetic moments are located on the other dopant atoms in Ag₅X^0,−.     

Peierls‐Distorted Monoclinic MnB4 with a MnMn Bond

Tetraborides of chromium and manganese exhibit an unusual boron‐atom framework that resembles the hypothetical tetragonal diamond. They are believed to be very hard. Single crystals of MnB₄ have now been grown. The compound crystallizes in the monoclinic crystal system (space group P2₁/c) with a structure that has four crystallographically independent boron‐atom positions, as confirmed by ¹¹B MAS‐NMR spectroscopy. An unexpected short distance between the Mn atoms suggests a double Mn–Mn bond and is caused by Peierls distortion. The structure was solved using group‐subgroup‐relationships. DFT calculations indicate Mn^I centers and paramagnetism, as confirmed by magnetic measurements. The density of states shows a pseudo‐band gap at the Fermi energy and semiconducting behavior was observed for MnB₄.     

Atomic‐Scale Observation of the Metal–Promoter Interaction in Rh‐Based Syngas‐Upgrading Catalysts

The direct conversion of syngas to ethanol, typically using promoted Rh catalysts, is a cornerstone reaction in CO₂ utilization and hydrogen storage technologies. A rational catalyst development requires a detailed structural understanding of the activated catalyst and the role of promoters in driving chemoselectivity. Herein, we report a comprehensive atomic‐scale study of metal–promoter interactions in silica‐supported Rh, Rh–Mn, and Rh–Mn–Fe catalysts by aberration‐corrected (AC) TEM. While the catalytic reaction leads to the formation of a Rh carbide phase in the Rh–Mn/SiO₂ catalyst, the addition of Fe results in the formation of bimetallic Rh–Fe alloys, which further improves the selectivity and prevents the carbide formation. In all promoted catalysts, Mn is present as an oxide decorating the metal particles. Based on the atomic insight obtained, structural and electronic modifications induced by promoters are revealed and a basis for refined theoretical models is provided.     

Quantum-chemical modeling of the electronic structure and chemical bond of Sn<Subscript>0.875</Subscript>M<Subscript>0.125</Subscript>O<Subscript>2</Subscript> (M = Cr,Mn, Co)

The electronic structure of the Sn_0.875M_0.125O₂ compounds (M = Cr, Mn, Co) with a rutile structure and magnetic moments of the transition metal atoms in them were calculated by the ab initio spin-polarized linear muffin-tin orbital method. The electron density and electron localization function maps for these compounds were constructed. Based on these data, the effect of the composition of these phases on the electronic spectrum, chemical bond, and magnetic and transport properties were analyzed.     

High Magnetic Moments in Manganese‐Doped Silicon Clusters

We report on the structural, electronic, and magnetic properties of manganese‐doped silicon clusters cations, Si_nMn⁺ with n=6–10, 12–14, and 16, using mass spectrometry and infrared spectroscopy in combination with density functional theory computations. This combined experimental and theoretical study allows several structures to be identified. All the exohedral Si_nMn⁺ (n=6–10) clusters are found to be substitutive derivatives of the bare Si_n+1⁺ cations, while the endohedral Si_nMn⁺ (n=12–14 and 16) clusters adopt fullerene‐like structures. The hybrid B3P86 functional is shown to be appropriate in predicting the ground electronic states of the clusters and in reproducing their infrared spectra. The clusters turn out to have high magnetic moments localized on Mn. In particular the Mn atoms in the exohedral Si_nMn⁺ (n=6–10) clusters have local magnetic moments of 4 μ_B or 6 μ_B and can be considered as magnetic copies of the silicon atoms. Opposed to other 3d transition‐metal dopants, the local magnetic moment of the Mn atom is not completely quenched when encapsulated in a silicon cage.     

Structural analysis of Gd6FeBi2 from single‐crystal X‐ray diffraction methods and electronic structure calculations

The crystal structure of the gadolinium iron bismuthide Gd₆FeBi₂ has been characterized by single‐crystal X‐ray diffraction data and analyzed in detail using first‐principles calculations. The structure is isotypic with the Zr₆CoAl₂ structure, which is a variant of the ZrNiAl structure and its binary prototype Fe₂P (Pearson code hP9, Wyckoff sequence g f d a). As such, the structure is best viewed as an array of tricapped trigonal prisms of Gd atoms centered alternately by Fe and Bi. The magnetic‐ordering temperature of this compound (ca 350 K) is much higher than that of other rare‐earth metal‐rich phases with the same or related structures. It is also higher than the ordering temperature of many other Gd‐rich ternary phases, where the magnetic exchange is typically governed by Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions. First‐principles calculations reveal a larger than expected Gd magnetic moment, with the additional contribution arising from the Gd 5d electrons. The electronic structure analysis suggests strong Gd 5d–Fe 3d hybridization to be the cause of this effect, rather than weak interactions between Gd and Bi. These details are of importance for understanding the magnetic response and explaining the high ordering temperature in this material.     

Kinetic study of the Ce(III)‐, Mn(II)‐ or Fe(phen)32+‐catalyzed Belousov–Zhabotinsky reaction with ethyl hydrogen malonate

In a stirred batch reaction, Fe(phen)₃²⁺ ion behaves differently from Ce(III) or Mn(II) ion in catalyzing the bromate‐driven oscillating reaction with ethyl hydrogen malonate [CH₂COOHCOOEt, ethyl hydrogen malonate (EHM)]. The effects of N₂ atmosphere, concentrations of bromate ion, EHM, metal ion catalyst, sulfuric acid, and additive (bromide ion or bromomalonic acid) on the pattern of oscillations were investigated. The kinetic study of the reaction of EHM with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion indicates that under aerobic or anaerobic conditions the order of reactivity toward reacting with EHM is Mn(III) > Ce(IV) ≫ Fe(phen)₃³⁺, which follows the same trend as that of the malonic acid system. The presence of the ester group in EHM lowers the reactivity of the two methylene hydrogen atoms toward bromination or oxidation by Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion. No good oscillations were observed for the BrO₃₋‐CH₂(COOEt)₂ reaction catalyzed by Ce(III), Mn(II), or Fe(phen)₃²⁺ ion. A discussion of the effects of oxygen on the reactions of malonic acid and its derivatives (RCHCOOHCOOR′) with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion is also presented. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 52–61, 2000     

混合价双核锰[Mn2(cyclen)2(μ-O)2](ClO4)3·4H2O的晶体结构和表征

The mixed-valence manganese(Ⅲ/Ⅳ) complex [Mn2(cyclen)2(μ-O)2](ClO4)3-4H2O (1) (cyclen=1,4,7,10-tetraazacyclododecan) with chemical formula C16H48Cl3Mn2N8O18 has been synthesized and characterized by single crystal X-ray diffraction analysis, elemental analysis, IR and electronic spectra. The results showed that the manganese(Ⅲ/Ⅳ) ions were six-coordinated by four nitrogen atoms from cyclen and two oxygen atoms from the oxygen bridge, forming a distorted octahedron geometry. There were two very strong peaks in the range of 400-700 nm in electronic spectrum, which was similar to Mn catalase and Mn ribonucleotide reductase extracted from organisms.Electrochemical study indicated that the complex underwent a quasi-reversible one-electron reduction and oxidation at E1/2=0.827 V in acetonitrile.     

Electronic and magnetic properties of manganese and iron-doped Ga(n)As(n) nanocages (n=7-12)

The electronic and magnetic properties of Mn- or Fe-doped Ga(n)As(n) (n=7-12) nanocages were studied using gradient-corrected density-functional theory considering doping at substitutional, endohedral, and exohedral sites. When doped with one atom, the most energetically favorable site gradually moves from surface (n=7-11) to interior (n=12) sites for the Mn atom, while the most preferred doping site of the Fe atom alternates between the surface (n=7,9,11) and interior (n=8,10,12) sites. All of the ground-state structures of Mn@Ga(n)As(n) have the atomlike magnetic moment of 5mu(B), while the total magnetic moments of the most stable Fe@Ga(n)As(n) cages for each size are about 2mu(B) except for the 4mu(B) magnetic moment of Fe@Ga(12)As(12). Charge transfer and hybridization between the 4s and 3d states of Mn or Fe and the 4s and 4p states of As were found. The antiferromagnetic (AFM) state of Mn(2)@Ga(n)As(n) is more energetically favorable than the ferromagnetic (FM) state. However, for Fe(2)@Ga(n)As(n) the FM state is more stable than the AFM state. The local magnetic moments of Mn and Fe atoms in the Ga(n)As(n) cages are about 4mu(B) and 3mu(B) in the FM and AFM states, respectively. For both Mn and Fe bidoping, the most energetically favorable doping sites of the transition metal atoms are located on the surface of the Ga(n)As(n) cages. The computed magnetic moments of the doped Fe and Mn atoms agree excellently with the theoretical and experimental values in the Fe(Mn)GaAs interface as well as (Ga, Mn)As dilute magnetic semiconductors.     

Kinetic study of the Ce(III)‐, Mn(II)‐ or Fe(phen)32+‐catalyzed Belousov‐Zhabotinsky reaction with 2‐ketoglutaric acid

The Belousov‐Zhabotinsky (BZ) reaction of bromate ion with 2‐ketoglutaric acid (KGA) in aqueous sulfuric acid catalyzed by Ce(III), Mn(II), or Fe(phen)₃²⁺ ion exhibits sustained barely damped oscillations under aerobic conditions. In general, the reaction oscillates without an induction period. Fe(phen)₃²⁺ ion behaves differently from Ce(III) and Mn(II) ions in catalyzing this oscillating system. The gem‐diol form of KGA exhibits different behavior from that of the keto form of KGA in the BZ reaction. The kinetics and mechanism of the reaction of KGA with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion was investigated. The order of relative reactivities of metal ions toward reaction with KGA is Mn(III) > Ce(IV) ≫ Fe(phen)₃³⁺. Experimental results are rationalized. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 101–107, 2001     

Kinetic study of the Ce(III)‐, Mn(II)‐, or ferroin‐catalyzed Belousov‐Zhabotinsky reaction with pyruvic acid

The Ce(III)‐, Mn(II)‐, or ferroin (Fe(phen)₃²⁺)‐catalyzed reaction of bromate ion and pyruvic acid (PA) or its dimer exhibits oscillatory behavior. Both the open‐chain dimer (parapyruvic acid, γ‐methyl‐γ‐hydroxyl‐α‐keto‐glutaric acid, DPA1) and the cyclic‐form dimer (α‐keto‐γ‐valerolactone‐γ‐carboxylic acid, DPA2) show more sustained oscillations than PA monomer. Ferroin behaves differently from Ce(III) or Mn(II) ion in catalyzing these oscillating systems. The kinetics of reactions of PA, 3‐brompyruvic acid (BrPA), DPA1, or DPA2 with Ce(IV), Mn(III), Fe(phen)₃³⁺ ion were investigated. The order of relative reactivity of pyruvic acids toward reaction with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion is DPA2 > DPA1 > BrPA > PA and that of metal ions toward reaction with pyruvic acids is Mn(III) > Ce(IV) > Fe(phen)₃³⁺. The rates of bromination reactions of pyruvic acids are independent of the concentration of bromine and the order of reactivity toward bromination is (DPA1, DPA2) > BrPA > PA. Experimental results are rationalized. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 408–418, 2000     

Synthesis, Thermal, Electrical and Catalytic Studies of Some Transition Metal Polychelates of Bis-bidentate Schiff Base

Polychelates of Mn（Ⅱ）, Fe（Ⅱ）, Co（Ⅱ）, Ni（Ⅱ）, Cu（Ⅱ）, Zn（Ⅱ） and Cd（Ⅱ） with the bis salen-type ligand derived from 4,4＇-bis[（salicylaldehyde-5）azo]biphenyl and 1,4-diaminobutane have been synthesized. All the polychelalls have been characllrized by elemental analysis, magnetic susceptibility measurements, IR, electronic spectra and thennogravirncuic studies. All the complexes isolated in solid stall are dark coloured and insoluble in water and common organic solvents. The ligand behaves as a bis-bidentall molecule coordinating through the phenolic oxygen and azomethine nitrogen atoms. The thermal decomposition of these metal complexes was investigated by thermogravimetric analysis and data have been analyzed for kinetic parameters using Broido equation. The solid-state electrical conductivity of the ligand and its polychelalls in the form of compressed pellet was studied in the temperaturc range from 313 to 413 K All the polychelalls were found to show semiconducting nature. The Mn（Ⅱ）, Fe（Ⅱ）, Co（Ⅱ） and Ni（Ⅱ） polychelalls have been assessed for the catalytic epoxidation of styrene.     

In‐situ XAFS Studies of Mn12 Molecular‐Cluster Batteries: Super‐Reduced Mn12 Clusters in Solid‐State Electrochemistry

In situ X‐ray absorption fine structure (XAFS) analyses were performed on rechargeable molecular cluster batteries (MCBs), which were formed by a lithium anode and cathode‐active material, [Mn₁₂O₁₂(CH₃CH₂C(CH₃)₂COO)₁₆(H₂O)₄] with tert‐pentyl carboxylate ligand (abbreviated as Mn12tPe), and with eight Mn³⁺ and four Mn⁴⁺ centers. This mixed valence cluster compound is used in an effort to develop a reusable in situ battery cell that is suitable for such long‐term performance tests. The Mn12tPe MCBs exhibit a large capacity of approximately 210 Ah kg⁻¹ in the voltage range V=4.0–2.0 V. The X‐ray absorption near‐edge structure (XANES) spectra exhibit a systematic change during the charging/discharging with an isosbestic point at 6555 eV, which strongly suggests that only either the Mn³⁺ or Mn⁴⁺ ions in the Mn12 skeleton are involved in this battery reaction. The averaged manganese valence, determined from the absorption‐edge energy, decreased monotonically from 3.3 to 2.5 in the first half of the discharging (4.0>V>2.8 V), but changed little in the second half (2.8>V>2.0 V). The former valence change indicates a reduction of the initial [Mn12]⁰ state by approximately ten electrons, which corresponds well with the half value of the observed capacity. Therefore, the large capacity of the Mn12 MCBs can be understood as being due to a combination of the redox change of the manganese ions and presumably a capacitance effect. The extended X‐ray absorption fine structure (EXAFS) indicates a gradual increase of the Mn²⁺ sites in the first half of the discharging, which is consistent with the XANES spectra. It can be concluded that the Mn12tPe MCBs would include a solid‐state electrochemical reaction, mainly between the neutral state [Mn12]⁰ and the super‐reduced state [Mn12]⁸⁻ that is obtained by a local reduction of the eight Mn³⁺ ions in Mn12 toward Mn²⁺ ions.     

A 1,2,4‐Triazole‐based Polynuclear Mixed‐valence MnIIMnIII Complex: Synthesis,Characterization, and Magnetic Property

A mixed‐valence Mn complex {[Mn^IIMn^III(HL)₂(4,4′‐bpy)(H₂O)₂] · (ClO₄)(DMF)₃(4,4′‐bpy)_0.5}_n ( 1 ) [H₂L = 3‐(2‐phenol)‐5‐(pyridin‐2‐yl)‐1,2,4‐triazole] was synthesized and characterized by X‐ray single‐crystal structure analysis and magnetic susceptibility. Single‐crystal X‐ray analysis revealed that complex 1 has a dinuclear core, in which adjacent central Mn^III atoms are linked by 4,4′‐bipyridine to form an infinite one‐dimensional (1D) molecular configuration. According to the Mn surrounding bond lengths and bond valence sum (BVS) calculations, we demonstrated that the Mn atom coordinated to the pyridine N atoms is in the +2 oxidation state, while another Mn atom coordinated to the phenolic oxygen atoms is in the +3 oxidation state. Magnetic susceptibility data of the complex 1 indicate that the ferromagnetic interaction dominates in this complex.