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.     

Structural and electronic properties of defective 2D transition metal dichalcogenide heterostructures

We present a first-principles study on the structure-property relationships in MoS₂ and WS₂ monolayers and their vertically stacked hetero-bilayer, with and without Sulfur vacancies, in order to dissect the electronic features behind their photocatalytic water splitting capabilities. We also benchmark the accuracy of three different exchange-correlation density functionals for both minimum-energy geometries and electronic structure. The best compromise between computational cost and qualitative accuracy is achieved with the HSE06 density functional on top of Perdew–Burke–Ernzerhof minima, including dispersion with Grimme's D3 scheme. This computational approach predicts the presence of mid-gap states for defective monolayers, in accordance with the present literature. For the heterojunction, we find unexpected vacancy-position dependent electronic features: the location of the defects leads either to mid-gap trap states, detrimental for photocatalyst or to a modification of characteristic type II band alignment behavior, responsible for interlayer charge separation and low recombination rates.     

The study of electronic and optical properties of ZnO/MoS2 and its vacancy heterostructures by first principles

Based on the first principles calculation, the effects of vacancies on the structural, electronic and optical properties of ZnO/MoS₂ heterostructure are investigated in this work. The results show that vacancies could exist stably in the heterojunctions and cause a significant decrease in bandgap. ZnO/MoS₂ with an O vacancy maintains semiconductor property with a bandgap of 0.119 eV, while heterostructure with a Zn vacancy exhibits metallic characteristic. Furthermore, the absorption capability of defective heterojunctions has been extended to infrared light region with obvious redshift. To sum up, vacancy engineering effectively changes the electronic and optical properties of ZnO/MoS₂ heterostructure, which provides a feasible approach for adjusting the optoelectronic properties of two-dimensional heterostructures and broadening their application in functional nanoelectronic and optoelectronic devices.     

Benchmarking approximate density functional theory. I. s/d excitation energies in 3d transition metal cations

The performance of a number of different implementations of density functional theory (DFT) for predicting the s/d interconfigurational energies of the 3d transition metal cations is investigated. Systematic comparisons of computed results with experimental data indicate that gradient corrected correlation functionals, like the LYP GGA, efficiently correct the flaws of the LDA, but reveal shortcomings in the treatment of exchange by currently available GGAs. The admixture of exact exchange in hybrid functionals eventually leads to largely reduced errors. Several basis sets available for the 3d elements are tested in combination with the B3LYP functional. Finally, the influence of variations of the admixture of exact exchange is systematically tested. The results reveal that computed s/d excitation energies obtained for the individual ions depend in markedly different ways on the amount of exact exchange admixture and that there is no single optimal and transferable exchange parameter to create a hybrid functional that yields improved results for all ions alike. Several of the recently devised functionals perform as good as or slightly better than the B3LYP functional in the present study. But given the fact that the B3LYP functional has been identified as the most successful DFT method in an overwhelming number of systematic investigations in very many areas of chemical research, there is no persuasive motivation to recommend its replacement by one of the other functionals, as much less is known about their robustness.     

三唑-芳香多羧酸类混配金属配合物的结构与磁性能研究

以三唑为主配体的过渡金属配合物以其结构多样性及在磁性、吸附等功能材料中的潜在应用而成为众多科研工作者的研究热点内容之一．本文从三唑一芳香多羧酸混配配合物的合成以及芳香酸对配合物中金属一三唑次级结构的调节角度,总结了近年来报道的该类混配金属配合物的结构多样性．在此基础上,初步关联了该类混合配体顺磁金属配合物的磁一构关系．     

Electronic structures and chemical bonding in 4d transition metal monohalides

Bond distances, vibrational frequencies, dipole moments, dissociation energies, electron affinities, and ionization potentials of MX (XM = Y-Cd, X = F, Cl, Br, I) molecules in neutral, positively, and negatively charged ions were studied by density functional method, B3LYP. The bonding patterns were analyzed and compared with both the available data and across the series. It was found that besides ionic component, covalent bonds are formed between the 4d transition metal s, d orbitals, and the p orbital of halogen. For both neutral and charged molecules, the fluorides have the shortest bond distance, iodides the longest. Although the opposite situation is observed for vibrational frequency, that is, fluorides have the largest value, iodides the smallest. For neutral and anionic species, the dissociation energy tends to decrease with the increasing atomic number from Y to Cd, suggesting the decreasing or weakening of the bond strength. For cationic species, the trend is observed from Y to Ag.     

Dipolar and electronic effects on charge transport through single transition metal complexes

Charge transport through single molecular neutral monoand di-cobalt(II) complexes with π-conjugated macromolecular wire was investigated.Scanning tunnelling spectroscopy (STS) studies revealed that the mono-cobalt(II) complex showed a pronounced rectifying effect with a large rectification ratio and finely featured NDR peaks,while the di-cobalt(II) complex showed a relatively symmetric electron transport without clear NDR peaks.Th     

Comparative study of magnetic and electronic properties of room-temperature polar magnets ScFeO3 and InFeO3

We performed calculations based on collinear and non-collinear spin density functional theory to investigate magnetic and electronic properties of new room-temperature polar magnetic compounds AFeO₃ (A = Sc, In). Exchange and correlation effects were simulated by standard local spin density approximation and the generalized gradient approximation. We determined that the canted G-type antiferromagnetic (G-AFM) structure of the Fe spin moments is the most stable magnetic structure for both compounds, in accordance with experimental facts. The calculated Fe spin magnetic moments and resulting weak ferromagnetic components perpendicular to the c-axis also agree well with the experiment. The magnitude of the Fe spin moment does not depend on the fact if the G-AFM structure is collinear or canted. The energy difference between these two structures is found to be much larger for InFeO₃, so as the exchange interaction constant J_nn between nearest-neighbor magnetic Fe ions. The ScFeO₃ and InFeO₃ electronic structures, which reproduce well their magnetic properties are presented and discussed. By comparing them with the band structures of some typical multiferroics, we conclude that different electronic mechanisms should be responsible for their ferroelectric distortion. In ScFeO₃, the cause of this distortion should be attributed to the hybridization between almost empty Sc 3d and occupied O 2p states along the hexagonal c-axis. For InFeO₃, however, the stereochemical activity of the In 5s localized electrons should be the principal driving force for ferroelectric distortion.     

Structure and magnetic exchange in heterometallic 3d-3d transition metal triethanolamine clusters

Synthetic methods are described that have resulted in the formation of seven heterometallic complexes, all of which contain partially deprotonated forms of the ligand triethanolamine (teaH(3)). These compounds are [Mn(III)(4)Co(III)(2)Co(II)(2)O(2)(teaH(2))(2)(teaH)(0.82)(dea)(3.18)(O(2)CMe)(2)(OMe)(2)](BF(4))(2)(O(2)CMe)(2)·3.18MeOH·H(2)O (1), [Mn(II)(2)Mn(III)(2)Co(III)(2)(teaH)(4)(OMe)(2)(acac)(4)](NO(3))(2)·2MeOH (2), [Mn(III)(2)Ni(II)(4)(teaH)(4)(O(2)CMe)(6)]·2MeCN (3), [Mn(III)(2)Co(II)(2)(teaH)(2)(sal)(2)(acac)(2)(MeOH)(2)]·2MeOH (4), [Mn(II)(2)Fe(III)(2)(teaH)(2)(paa)(4)](NO(3))(2)·2MeOH·CH(2)Cl(2) (5), [Mn(II)Mn(III)(2)Co(III)(2)O(teaH)(2)(dea)(Iso)(OMe)(F)(2)(Phen)(2)](BF(4))(NO(3))·3MeOH (6) and [Mn(II)(2)Mn(III)Co(III)(2)(OH)(teaH)(3)(teaH(2))(acac)(3)](NO(3))(2)·3CH(2)Cl(2) (7). All of the compounds contain manganese, combined with 3d transition metal ions such as Fe, Co and Ni. The crystal structures are described and examples of 'rods', tetranuclear 'butterfly' and 'triangular' Mn(3) cluster motifs, flanked in some cases by diamagnetic cobalt(III) centres, are presented. Detailed DC and AC magnetic susceptibility and magnetization studies, combined with spin Hamiltonian analysis, have yielded J values and identified the spin ground states. In most cases, the energies of the low-lying excited states have also been obtained. The features of note include the 'inverse butterfly' spin arrangement in 2, 4 and 5. A S = 5/2 ground state occurs, for the first time, in the Mn(III)(2)Mn(II) triangular moiety within 6, the many other reported [Mn(3)O](6+) examples having S = ? or 3/2 ground states. Compound 7 provides the first example of a Mn(II)(2)Mn(III) triangle, here within a pentanuclear Mn(3)Co(2) cluster.     

Relaxations of confined chains in polymer nanocomposites: Glass transition properties of poly(ethylene oxide) intercalated in montmorillonite

The relaxation behavior of poly(ethylene oxide) (PEO), intercalated in montmorillonite, a naturally occurring mica-type silicate, was studied by differential scanning calorimetry (DSC) and thermally stimulated dielectric depolarization (or thermally stimulated current, TSC). The materials were synthesized by melt or solution-mediated intercalation. In both intercalates, the PEO chains were confined to ca. 0.8-nm galleries between the silicate layers. The solution intercalate contained a fraction of unintercalated PEO chains which exhibited a weak and depressed PEO melting endotherm in DSC. In contrast, the melt intercalate was “starved” such that almost all the PEO chains were effectively intercalated. For these melt intercalates, no thermal events were detected by DSC. TSC thermal sampling technique was used to examine the glass transition regions and to estimate the extent of cooperativity of chain motions. The motions of the intercalated PEO chains are inherently noncooperative relative to the cooperative T_g motions in the amorphous portion of the bulk polymer. This is presumably due to the strong confining effect of the silicate layers on the relaxations of the intercalated polymer. © 1997 John Wiley & Sons, Inc.     

Synthesis and characterization of tetra-armed-thiosemicarbazone and its salen/salophen capped transition metal complexes: Investigation of their thermal and magnetic properties

In this work, we aimed to synthesize and characterize a novel tetra-directional ligand, (2E,2′E)-2,2′-((((2-(1,3-bis(4-((E)-(2-carbamothioylhydrazono)methyl)phenoxy)propan-2-ylidene)propane-1,3-diyl)bis(oxy))bis(4,1-phenylene))bis(methanylylidene))bis(hydrazinecarbothioamide) (5), including thiosemicarbazone group and its novel tetra-directional-tetra-nuclear Schiff base complexes. For this purpose, we used 1,4-dibromo-2,3-bis(bromomethyl)but-2-ene (2) as starting material. 4,4′-((2-(1,3-Bis(4-formylphenoxy)propan-2-ylidene)propane-1,3-diyl) bis(oxy))dibenzaldehyde (3) was synthesized by the reaction of an equivalent 1,4-dibromo-2,3-bis(bromomethyl)but-2-ene (2) and 4 equivalents of 4-hydroxybenzaldehyde. Then, compound 5 was synthesized in high yield (86%) by a condensation reaction of compound 3 with thiosemicarbazide (4). Finally, four novel tetra-nuclear Cr(III) or Fe(III) complexes of compound 5 were synthesized. The synthesized compounds were characterized using elemental analyses, ¹H NMR, Fourier transform–infrared spectrometry, liquid chromatography–mass spectrometry (ESI⁺), and thermal analyses. The metal ratios of the prepared complexes were determined using an atomic absorption spectrophotometer. We also investigated their effects on the magnetic behaviors of [salen, salophen, Cr(III)/Fe(III)] capped complexes. The complexes were found to be low-spin distorted octahedral Fe(III) and distorted octahedral Cr(III), all bridged by thiosemicarbazone.     

荷电(±1)对二十面体X_(13)(X=Cr,Mn,Fe,Co)团簇的稳定性与磁性的影响

采用基于密度泛函理论的计算方法,对正二十面体金属X13(X=Cr,Mn,Fe,Co)中性和荷电团簇进行了全面的结构优化计算,研究了荷电对团簇的稳定性和磁性的影响.结果表明:荷负电能够使团簇的稳定性增强;荷电对不同团簇的原子间距离的影响不同;同时荷电对不同团簇磁性的影响也是不一样的,尤其是荷负电能够使Fe13和Co13团簇的磁性大大增强;荷电对不同团簇磁性的影响不是通过原子间距离的变化来实现的,而是受到原子内部电荷的转移和杂化程度的影响.     

TDDFT studies of electronic structure and first hyperpolarizability of terta-nuclear cubane-like transition metal clusters

The TDDFT method is first applied in a series of tetra-nuclear transition metal clusters studies for nonlinear optical properties. The results indicate that the charge transfer inside the metal core [MCu3X4] (M=W, Mo; X=S, O, Cl, Se, Br) makes contribution to the optical nonlinearity. It is possible to enhance the hyperpolarizability by substituting the ligands of the clusters.     

Benchmarking approximate density functional theory for s/d excitation energies in 3d transition metal cations

Holthausen has recently provided a comprehensive study of density functional theory for calculating the s/d excitation energies of the 3d transition metal cations. This study did not include the effects of scalar relativistic effects, and we show here that the inclusion of scalar relativistic effects significantly alters the conclusions of the study. We find, contrary to the previous study, that local functionals are more accurate for the excitation energies of 3d transition method cations than hybrid functionals. The most accurate functionals, of the 38 tested, are SLYP, PBE, BP86, PBELYP, and PW91.     

Transition metal coordination complexes based on V-shaped bis-triazole ligand: syntheses,structures, and properties

Hydrothermal reactions of 1,3-bis(1,2,4-triazol-1-yl)benzene (btb) and M(NO₃)₂ (M = Co²⁺ (1), Cu²⁺ (2)) afforded two new coordination polymers, [Co(btb)₂(NO₃)(H₂O)]_n·NO₃·H₂O (1) and [Cu(btb)₂(NO₃)₂]_n (2), respectively. Single-crystal X-ray diffraction reveals that 1 crystallizes in the space group P2₁/m and 2 crystallizes in the space group Pī, both showing a double-stranded chain structure. The 1-D chains are interconnected via π?π interactions to lead to 2-D ladder-like supramolecular architectures. In addition, magnetic behavior and thermal stability of 1 and 2 have been investigated. For 1, weak antiferromagnetic interactions are observed at low temperature, and the data obey the Curie–Weiss law χ_M = C/(T?θ), with C = 3.22 cm³·mol^?1·K and θ = ?10.39 K. For 2, the decrease of the χT vs. T curve at low temperature is the result of intermolecular antiferromagnetic magnetic interactions.     

Geometry and electronic properties of alkali metal (rubidium) doped boron clusters

Alkali metal-doped boron clusters have captured much attention because of their novel electronic properties and structural evolution. In the study of RbB_n^0/− (n = 2–12) clusters, the minimum global search of the potential energy surface and structure optimization at the level of PBE1PBE by using the CALYPSO method and Gaussian package coupled with DFT calculation; the geometrical structures and electronic properties are systematically investigated. At n = 8, the ground-state structures are composed of an Rb atom above B atoms, forming a structurally stable pagoda cone. By stability analysis and charge transfer calculation, the RbB₈⁻ cluster shows more stability. It found that s-p hybridization between Rb atom and B atoms as well as s-p hybridization between B atoms is one of the reasons for the outstanding stability exhibited in the RbB₈^0/− clusters by using DOS and HOMO–LUMO orbital contour maps. The chemical bonding of the RbB₈^0/− groups was analyzed by using the AdNDP method, and B atoms with larger numbers readily form multi-center chemical bonds with the Rb atom. From the results of the bonding analysis, the interaction between the Rb atom and B atoms strengthens the stability of the RbB₈^0/− clusters. It is hoped that this work provides a direction for experimental manipulation.     

Electrochemical synthesis and properties of δ-fluoroacyl and δ-perfluoroalkyl transition metal complexes

The electrochemical synthesis of δ-fluoroacyl complexes [M]-δ-COR_f(M=C₅H₅(CO)₃W or (CO)₅Mn; R_f=CF₃ or C₄F₉) was performed according to two procedures: (1) the preliminary electrochemical synthesis of [M]⁻ from [M]₂ followed by reaction with a fluorine-containing compound and (2) the electrochemical synthesis of [M]⁻ in the presence of a fluorine-containing compound. Trifluoroacetic anhydride was demonstrated to be the best acylating agent in these reactions. The electrochemical properties of the resulting complexes were studied. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 373–375, February, 2000.     

Thermal relaxation in excited electronic states of d and d metal complexes

Photophysical kinetic results have played an important role in assessing excited state relaxation pathways in transition metal complexes. The applicability of a kinetic analysis is critically dependent on the quality of the individual decay rates, the temperature range examined, and the model used to extract the activation parameters. The extensive literature describing the temperature dependence of excited state depopulation in d³ and d⁶ complexes permits an evaluation of both the power and limitations of kinetic arguments in assessing the mechanism of excited state relaxation.     

以[M(DETA)2)]n+(M=Cu2+, Ni2+, Co3+)为客体的MnPS3夹层化合物的合成、结构表征与磁性研究

将过渡金属配合物阳离子([M(DETA)₂]ⁿ⁺(M=Cu²⁺,Ni²⁺,Co³⁺;DETA=Diethylenetriamine,二乙烯三胺)作为客体插入层状MnPS₃层间得到了相应的3个夹层化合物。通过X-射线粉末衍射、元素分析和红外光谱对夹层化合物的结构进行了表征。结果表明,与主体MnPS₃ 0.65 nm的层间距相比较,夹层化合物(Mn_0.88PS₃[Cu(DETA)₂]_0.12)的层间距扩大了0.32 nm,由此推测客体[Cu(DETA)₂]²⁺在层间以平面四方的配位形式存在,而另2个夹层化合物(Mn_0.79PS₃[Ni(DETA)₂]_0.21和Mn_0.74PS₃[Co(DETA)₂]_0.17)的层间距扩大了0.48 nm,说明客体[(M(DETA)₂]ⁿ⁺,M=Co³⁺,Ni²⁺) 在主体层间以八面体配位形式存在。磁性测试结果表明过渡金属离子[(M(DETA)₂]ⁿ⁺(M=Cu²⁺,Co³⁺)的插入能引起主体MnPS₃的磁性在35~40 K发生由顺磁向亚铁磁性的转变并表现自发磁化,而客体[Ni(DETA)₂]²⁺却使夹层化合物的反铁磁相互作用增强,抑制了自发磁化的发生。     

Structures and electronic and magnetic properties of the 3d transition metal-substituted TMC5N8 clusters

Research on Chemical Intermediates - The structures and electronic and spin properties of the 3d TMC5N8 clusters have been calculated using the PBE functional. The results demonstrate that the Zn...