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.     

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,−.     

Structures,magnetic properties,and electronic counting rule of metals‐encapsulated cage‐like M2 Si18 (M = Ti‐Zn) clusters

The geometries, magnetic properties and stabilities of the transition metal (TM) atoms encapsulated M₂Si₁₈ (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) clusters have been systematically calculated by using the density function theory with generalized gradient approximation. Only when the doping metal atom has no more than half‐full d electronic shell, a double hexagonal prism cage‐like M₂Si₁₈ structure could form. The total moments of M₂Si₁₈ are either 0 or 2μ_B. Co₂Si₁₈ is the most stable cluster among all 3d doped M₂Si₁₈ clusters. The model of shell closure at the TM atom may be helpful to understand the stability of M₂Si₁₈ clusters. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Electronic Properties of Transition‐Metal‐Decorated Silicene

The electronic properties of 3d transition metal (TM)‐decorated silicene were investigated by using density functional calculations in an attempt to replace graphene in electronic applications, owing to its better compatibility with Si‐based technology. Among the ten types of TM‐doped silicene (TM–silicene) studied, Ti‐, Ni‐, and Zn‐doped silicene became semiconductors, whereas Co and Cu doping changed the substrate to a half‐metallic material. Interestingly, in cases of Ti‐ and Cu‐doped silicene, the measured band gaps turned out to be significantly larger than the previously reported band gap in silicene. The observed band‐gap openings at the Fermi level were induced by breaking the sublattice symmetry caused by two structural changes, that is, the Jahn–Teller distortion and protrusion of the TM atom. The present calculation of the band gap in TM–silicene suggests useful guidance for future experiments to fabricate various silicene‐based applications such as a field‐effect transistor, single‐spin electron source, and nonvolatile magnetic random‐access memory.     

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.     

Adsorption of transition-metal atoms on boron nitride nanotube: a density-functional study

Adsorption of transition atoms on a (8,0) zigzag single-walled boron nitride (BN) nanotube has been investigated using density-functional theory methods. Main focuses have been placed on configurations corresponding to the located minima of the adsorbates, the corresponding binding energies, and the modified electronic properties of the BN nanotubes due to the adsorbates. We have systemically studied a series of metal adsorbates including all 3d transition-metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) and two group-VIIIA transition-metal elements (Pd and Pt). We found that many transition-metal atoms can be chemically adsorbed on the outer surface of the BN nanotubes and that the adsorption process is typically exothermic. Upon adsorption, the binding energies of the Sc, Ti, Ni, Pd, and Pt atoms are relatively high (>1.0 eV), while those of V, Fe, and Co atoms are modest, ranging from 0.62 to 0.92 eV. Mn atom forms a weak bond with the BN nanotube, while Zn atom cannot be chemically adsorbed on the BN nanotube. In most cases, the adsorption of transition-metal atoms can induce certain impurity states within the band gap of the pristine BN nanotube, thereby reducing the band gap. Most metal-adsorbed BN nanotubes exhibit nonzero magnetic moments, contributed largely by the transition-metal atoms.     

Reactions of first-row transition metal ions with propargyl alcohol in the gas phase

The gas-phase reactions with propargyl alcohol (PPA) of all the singly charged ions of the first-row transition metals, generated by laser ablation in an external ion source, were studied by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS.). The reactivities of the metal ions change irregularly across the periodic table, and the reactivity of each ion is a function of its electronic configuration and corresponding metal-oxygen (M-O) bond energies. The 10 metal ions were classified into three categories according to their reactivities: Sc(+), Ti(+) and V(+) are the most reactive ions which react with PPA to give many kinds of oxygen-rich products due to stronger M-O bonds; Fe(+), Co(+) and Ni(+) are less reactive; Cr(+), Mn(+), Cu(+) and Zn(+) are the most unreactive ions, due to the half and completely occupied valence electronic configurations. The order of reactivity is Ti(+) > V(+) > Sc(+) > Co(+) > Fe(+) approximately Ni(+) > Zn(+) > Cr(+) approximately Mn(+) approximately Cu(+).     

Improvement in Hydrogen Desorption from β‐ and γ‐MgH2 upon Transition‐Metal Doping

A thorough study of the structural, electronic, and hydrogen‐desorption properties of β‐ and γ‐MgH₂ phases substituted by selected transition metals (TMs) is performed through first‐principles calculations based on density functional theory (DFT). The TMs considered herein include Sc, V, Fe, Co, Ni, Cu, Y, Zr, and Nb, which substitute for Mg at a doping concentration of 3.125 % in both the hydrides. This insertion of TMs causes a variation in the cell volumes of β‐ and γ‐MgH₂. The majority of the TM dopants decrease the lattice constants, with Ni resulting in the largest reduction. From the formation‐energy calculations, it is predicted that except for Cu and Ni, the mixing of all the selected TM dopants with the MgH₂ phases is exothermic. The selected TMs also influence the stability of both β‐ and γ‐MgH₂ and cause destabilization by weakening the Mg?H bonds. Our results show that doping with certain TMs can facilitate desorption of hydrogen from β‐ and γ‐MgH₂ at much lower temperatures than from their pure forms. The hydrogen adsorption strengths are also studied by density‐of‐states analysis.     

影响TiAl合金塑性的电子结构因素

应用ＥＨＴ紧束缚能带计算方法, 系统研究了Ｔｉ－４８Ａｌ－２Ｍ 为模型的γ－ＴｉＡｌ掺杂合金的电子结构。发现能有效地改善合金塑性的元素Ｖ、Ｃｒ、Ｍｎ 主要在两方面改变了γ－ＴｉＡｌ合金的电子结构,即改善Ｔｉ周围成键强度的各向均衡性和改变Ｔｉ、Ａｌ参与成键的电子分布,使成键电子云的球形化成分增大。研究结果表明Ｖ、Ｃｒ、Ｍｎ 等取代Ａｌ时成键的均衡性及电子云球形化均增大,从而有利于材料变形改善塑性,而加入Ｆｅ、Ｃｏ、Ｎｉ虽然改善电子云的球形化但却不利于成键强度的均衡性,因而对合金的塑性无明显改善。     

Effect of 3<Emphasis Type="Italic">d</Emphasis>-metal dopants on the electronic properties of hexagonal titanium dioxide nanotubes

The electronic structure of hexagonal TiO₂ nanotubes doped with 3d transition metals from Sc to Zn was calculated by the linearized augmented cylindrical wave method. The calculated densities of states demonstrate that the substitution of Sc, V, Co, Cu, or Fe atoms for a part of Ti atoms leads to the decrease in the band gap width of the material from 4 to 2 eV. Such nanotubes are promising materials for creation of electrodes for electrochemical photolysis of water.     

Doping of Zinc Oxide with Selected First Row Transition Metals for Photocatalytic Applications

ZnO doped with Cr, Mn, Fe, Co, Ni and Cu was prepared by homogeneous hydrolysis of sulfates with urea. The samples were annealed at various temperatures and characterized by X‐ray powder diffraction, UV/VIS reflectance spectroscopy, BET (Brunauer‐Emmet‐Teller) surface area and porosity measurements. The photocatalytic activity of the samples was evaluated by measuring the degradation of an organic dye Reactive Black 5. The morphology of the samples was determined by scanning electron microscopy and atomic force microscopy. For the Cu‐doped ZnO sample, EPR spectra were obtained. All samples annealed at 800°C contained hexagonal ZnO. In the VIS region, the best photocatalytic performance had the ZnO samples doped with Cr, Fe and Cu.     

Determination of trace elements of some Egyptian crops by instrumental neutron activation,inductively coupled plasma-atomic emission spectrometric and flameless atomic absorption spectrophotometric analysis

Instrumental neutron activation analysis was used for the determination of Al, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, K, La, Mg, Mn, Na, Rb, Sb, Sc, Se, Ti, Th, V and Zn, ICP-AES for the determination Al, Ag, Ba, Be, Ca, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Na, Ni, P, Sc, Sr, Ti, V and Zn and flameless AAS for the determination of Cd, Hg and Pb in egg plant, potatoes, green pepper (Leguminosae), vegetable marrow (Cucurbitaceae), pears, apple (Rosaceae), castor oil plant (Euphorbiaceae), lettuce (compositae), dill, parsley, coriander (Umbelliferae), and in some soil samples collected from Aswan province.     

Stability and Catalytic Performance of Single-Atom Supported on Ti2CO2 for Low-Temperature CO Oxidation: A First-Principles Study

Based on first-principles calculations, the potential of Ti₂CO₂ monolayer (MXene) as a single-atom catalyst (SAC) support for 3d transition metal (TM) atoms (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) is studied for CO oxidation. We first screen the support effect according to the stability of a single metal atom and find that Sc and Ti supported on Ti₂CO₂ have stronger adsorption energy than the cohesive energy of their bulk counterparts and therefore, we selected Sc and Ti supported on Ti₂CO₂ for further catalytic reactions. The stability and the potential catalytic reactivity are verified by electronic structure and charge transfer analysis. Both Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms are considered in this study, and lower energy barriers of 0.002 and 0.37 eV were found in the ER mechanism compared to the LH mechanism, which are 0.25 and 0.34 eV for Sc and Ti catalysts, respectively. Moreover, kinetic ER and LH mechanisms are favorable for both Sc- and Ti/Ti₂CO₂ because of the comparable energy barrier to other metals and SAC supported on 2D materials. However, Ti/Ti₂CO₂ catalyst is thermodynamically unfavorable. Based on these calculations, we propose that Sc supported on Ti₂CO₂ is the best catalyst for CO-oxidation. The current study not only broadens the scope of the single-atom Sc catalyst but also extends the consideration of MXene support for catalyst optimization.     

Binuclear cyclopentadienylmetal cyclooctatetraene derivatives of the first row transition metals: effects of ring conformation on the bonding of an eight-membered carbocyclic ring to a pair of metal atoms

Binuclear Cp(2)M(2)(μ-C(8)H(8)) derivatives have been synthesized for M = V, Cr, Co, and Ni and have now been studied theoretically for the entire first row of transition metals from Ti to Ni. The early transition metal derivatives Cp(2)M(2)(μ-C(8)H(8)) (M = Ti, V, Cr. Mn) are predicted to form low-energy cis-Cp(2)M(2)(μ-C(8)H(8)) structures with a folded C(8)H(8) ring (dihedral angle ～130°) and short metal-metal distances suggesting multiple bonding. These predicted structures are close to the experimental structures for M = V, Cr with V≡V and Cr≡Cr bond lengths of ～2.48 and ～2.36 ?, respectively. The middle to late transition metals form trans-Cp(2)M(2)(μ-C(8)H(8)) structures (M = Mn, Fe, Co, Ni) with a twisted μ-C(8)H(8) ring and no metal-metal bonding. The hapticity of the central μ-C(8)H(8) ring in such structures ranges from five for Mn and Fe to four for Co and three for Ni and thus depend on the electronic requirements of the central metal atom. This leads to the favored 18-electron configuration for both metal atoms in the singlet Fe, Co, and Ni structures but only 17-electron metal configurations in the triplet Mn structure. In addition, the late transition metals form trans-Cp(2)M(2)(μ-C(8)H(8)) structures (M = Fe, Co, Ni), with the tub conformation of the μ-C(8)H(8) ring functioning as a tetrahapto (M = Fe, Co) or trihapto (M = Ni) ligand to each CpM group. A μ-C(8)H(8) ring in the tub conformation also bonds to two CpFe units as a bis(tetrahapto) ligand in both singlet and triplet cis-Cp(2)Fe(2)(μ-C(8)H(8)) structures.     

Homonuclear transition-metal trimers

Density-functional theory has been used to determine the ground-state geometries and electronic states for homonuclear transition-metal trimers constrained to equilateral triangle geometries. This represents the first application of consistent theoretical methods to all of the ten 3d block transition-metal trimers, from scandium to zinc. A search of the potential surfaces yields the following electronic ground states and bond lengths: Sc3(2A1',2.83 A), Ti3(7E',2.32 A), V3(2E",2.06 A), Cr3(17E',2.92 A), Mn3(16A2',2.73 A), Fe3(11E",2.24 A), Co3(6E",2.18 A), Ni3(3A2",2.23 A), Cu3(2E',2.37 A), and Zn3(1A1',2.93 A). Vibrational frequencies, several low-lying electronic states, and trends in bond lengths and atomization energies are discussed. The predicted dissociation energies DeltaE(M3-->M2+M) are 49.4 kcal mol(-1)(Sc3), 64.3 kcal mol(-1)(Ti3), 60.7 kcal mol(-1)(V3), 11.5 kcal mol(-1)(Cr3), 32.4 kcal mol(-1)(Mn3), 61.5 kcal mol(-1)(Fe3), 78.0 kcal mol(-1)(Co3), 86.1 kcal mol(-1)(Ni3), 26.8 kcal mol(-1)(Cu3), and 4.5 kcal mol(-1)(Zn3).     

Structural and Magnetic Properties of 3d Transition‐Metal‐Atom Adsorption on Perfect and Defective Graphene: A Density Functional Theory Study

We systematically investigate the interactions and magnetic properties of a series of 3d transition‐metal (TM; Sc–Ni) atoms adsorbed on perfect graphene (G₆), and on defective graphene with a single pentagon (G₅), a single heptagon (G₇), or a pentagon–heptagon pair (G₅₇) by means of spin‐polarized density functional calculations. The TM atoms tend to adsorb at hollow sites of the perfect and defective graphene, except for G₆Cr, G₅Cr, and G₅Ni. The binding energies of TMs on defective graphene are remarkably enhanced and show a V‐shape, with G_NCr and G_NMn having the lowest binding energies. Furthermore, complicated element‐ and defect‐dependent magnetic behavior is observed in G_NTM. Particularly, the magnetic moments of G_NTM linearly increase by about 1 μ_B and follow a hierarchy of G₇TM<G₅₇TM<G₅TM as the TM varies from Sc to Mn, and the magnetic moments begin to decrease afterward; by choosing different types of defects, the magnetic moments can be tuned over a broad range, for example, from 3 to 6 μ_B for G_NCr. The intriguing element‐ and defect‐dependent magnetic behavior is further understood from electron‐ and back‐donation mechanisms.     

Determination of impurities in nuclear fuel element components by neutron activation analysis

Neutron activation analysis methods for the determination of impurities in zirconium cladding material and uranium oxide are described. Detection limits for the elements Al, Cd, Cr, Co, Cu, Hf, Fe, Mn, Ni, W and U in zirconium are below that required by the ASTM B 352-79 standard. The method has been tested on the NIST SRM 360a Zircaloy-2 from which the elements Na, Mg, Al, Ca, V, Cr, Fe, Co, Ni, Cu, Eu and U have been detected. The values for Cr, Fe, Ni and Cu are compared with the certified values. A method for the pre-irradiation separation of the elements Mg, Na, Al, K, Sc, Ca, V, Mn, Cr, Fe, Co, Cu, Zn, Rb, Zr, Cd, Cs, REE and Hf from uranium has been developed. A neutron activation analysis method for the determination of those elements in uranium is described. The method is tested by the analysis of the IAEA reference sample SR-54/64. The elements Al, Mn, V, Cu, Cr, Co, Ni and Fe have been detected and the results compared with the certified values.     

Organic acid solutions in the chromatography of inorganic ions VIII. Cation-exchange of Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II), Fe(III), Sc(III), Y(III), Eu(III), Dy(III), Ho(III), Yb(III), Ti(IV) and Nb(V) in malate media

Summary The cation-exchange behaviour of Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II), Fe(III), Sc(III), Y(III), Eu(III), Dy(III), Ho(III), Yb(III), Ti(IV) and Nb(V) in malate media at various concentrations and pH, was studied with Dowex 50 WX8 resin (200–400 mesh) in the ammonium form. Separation of Fe(III)/Cu(II), Fe(III)/Cu(II)/Zn(II), Fe(III)/Co(II)/Mn(II), Cu(II)/Ni(II)/Mn(II), Fe(III)/Cu(II)/Co(II)/Mn(II), Fe(III)/Cu(II)/Ni(II)/Cd(II), Yb(III)/Eu(III), Sc(III)/Y(III),Sc(III)/Yb(III)/Dy(III) and Nb(V)/Yb(III)/Ho(III) has been achieved, among others.This work was supported by C.N.R. of Italy.     

The geometric, electronic, and magnetic properties of Ag5X+ (X = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) clusters

Density functional theory calculations are performed on small cationic transition metal doped silver clusters, Ag5X+ (X = Sc, Ti, V, Cr, Mn, Fe, Co, and Ni) using the B3LYP and BP86 functionals. Several two-dimensional and three-dimensional isomers with the dopant at a high coordinated site are found to be close in energy. The relative energy of the isomers is checked with CCSD(T). The interaction between the dopant 3d electrons and the host is discussed by considering the density of states and the shape of the molecular orbitals. A large local spin magnetic moment on the dopant atom is predicted.     

Electronic and magnetic properties of substituted BN sheets: a density functional theory study

Using density functional calculations, we investigate the geometries, electronic structures and magnetic properties of hexagonal BN sheets with 3d transition metal (TM) and nonmetal atoms embedded in three types of vacancies: V(B), V(N), and V(B+N). We show that some embedded configurations, except TM atoms in V(N) vacancy, are stable in BN sheets and yield interesting phenomena. For instance, the band gaps and magnetic moments of BN sheets can be tuned depending on the embedded dopant species and vacancy type. In particular, embedment such as Cr in V(B+N), Co in V(B), and Ni in V(B) leads to half-metallic BN sheets interesting for spin filter applications. From the investigation of Mn-chain (C(Mn)) embedments, a regular 1D structure can be formed in BN sheets as an electron waveguide, a metal nanometre wire with a single atom thickness.