Doping Of Transition Metal Atoms Research Articles

Effect of Doped Transition Metal Atoms on Structure and Nonlinear Optical Properties of Decaborane

In this study, electrical and nonlinear optical properties of decaborane (B10H14) were investigated using the density functional theory method when transition metal atoms (scandium, titanium and vanadium) were doped on the structure. Hydrogen and boron atoms in B10H14 were substituted by the transition metals. This doping process resulted in a drastic reduction in the energy gap of decaborane. First, the hyperpolarizability (β 0) of B10H14 dramatically increased in the presence of titanium (Ti) in the place of hydrogen atoms. The highest value of β 0 (≈ 98,387.90 a.u.) was obtained for B10TiH13 (in the S3 position) and calculated to be 1700 times larger than the β 0 value for B10H14 (≈57.82 a.u.). Therefore, the Ti-doped systems showed a significantly larger non-linear optical (NLO) response than the other studied transition metals, suggesting that its system might be useful as a promising NLO material.

Local atomic and electronic structure of quantum dots based on Mn- and Co-doped ZnS

Solid solutions of zinc sulfide with manganese and cobalt are synthesized. Based on the analysis of X-ray diffraction profiles the conclusion is drawn about the formation of a hexagonal wurtzite type structure in the synthesized quantum dot (QD) solutions. The average crystallite sizes are 8 nm and 22 nm for the samples with manganese and cobalt respectively. Results of IR and optical spectroscopy are consistent with the powder X-ray diffraction and X-ray fluorescence data. The question about particle aggregation in isopropanol and DMF solutions is considered. The QD structures based on ZnS particles doped with Mn and Co transition metal atoms are modeled. The possibility to apply X-ray absorption near edge structure (XANES) spectroscopy to verify the atomic structure parameters around the positions of doping transition metal atoms in QDs of the ZnS family is shown. Partial densities of ZnS:Mn and ZnS:Co electronic states are calculated.

Modification of the photocatalytic properties of anatase TiO2 (101) surface by doping transition metals

Exploring new types of photocatalysts and modifying the photocatalytic activity have attracted more and more extensive attention in many research fields. Anatase TiO2, a promising photocatalyst widely studied, can only absorb the ultraviolet light and thus only make little use of the power in visible light. Therefore, it is an urgent task to make theoretical and experimental investigations on the photocatalytic mechanism in anatase TiO2 and then improve its visible light response so as to utilize more visible light. Now, in the present paper, we carry out a systematic theoretical investigation on modifying the photocatalytic properties of the anatase TiO2 (101) surface via doping transition metal neutral atoms such as Fe, Ni, Pd, Pt, Cu, Ag, and Au by using the plane wave ultrasoft pseudopotential method of the density functional theory. The dependence of the macroscopic catalytic activity on electronic structure and optoelectronic property is uncovered by making a comparative analysis of the geometric structures, the electronic structures, and the optical properties of the undoped and doped anatase TiO2 (101) surfaces. Our numerical results show that doping certain transition metals can suppress the band gap or induce extra impurity energy levels, which is beneficial to improving the visible light response of the TiO2 (101) surface in different ways. In most cases, the new impurity energy levels will appear in the original band gap, which comes from the contribution of the d electronic states in the transition metal atoms. Moreover, the photocatalytic activity of the TiO2 (101) surface can be changed differently by doping different transition metal atoms, which is closely dependent on the bandgap width, Fermi energy, the impurity energy level, and the electron configuration of the outermost shell of the dopants. This research should be an instructive reference for designing TiO2 (101) photocatalyst and improving its capability, and also helpful for understanding doping transition metal atoms in other materials.

A first-principles study of transition metal doped arsenene

Arsenene is the monolayer gray arsenic which was proposed only recently. Herein, we study the magnetic properties and electronic structures of transition-metal-doped arsenene by using first-principles calculations. Three doping concentrations are considered in our investigation. The results show that not all 3d transition metal (TM) atoms can induce the magnetic state in arsenene. Moreover, the doping concentration hardly affects the magnetic moment except for Fe- and Ni-doped systems. We believe, in particular, that the magnetism is dominantly controlled by the doping TM atoms, and no significant contributions are induced, even by their nearest arsenic atoms. In addition, the multiplicate electronic structures of TM-doped arsenene, such as semiconductor, metal and half-metal, have also been revealed and discussed in this work, which may provide a new attention for the doped arsenene nanosheets.

Defect energetics and magnetic properties of 3d-transition-metal-doped topological crystalline insulator SnTe

The introduction of magnetism in SnTe-class topological crystalline insulators is a challenging subject with great importance in the quantum device applications. Based on the first-principles calculations, we have studied the defect energetics and magnetic properties of 3d transition-metal (TM)-doped SnTe. We find that the doped TM atoms prefer to stay in the neutral states and have comparatively high formation energies, suggesting that the uniform TMdoping in SnTe with a higher concentration will be difficult unless clustering. In the dilute doping regime, all the magnetic TMatoms are in the high-spin states, indicating that the spin splitting energy of 3d TM is stronger than the crystal splitting energy of the SnTe ligand. Importantly, Mn-doped SnTe has relatively low defect formation energy, largest local magnetic moment, and no defect levels in the bulk gap, suggesting that Mn is a promising magnetic dopant to realize the magnetic order for the theoretically-proposed large-Chern-number quantum anomalous Hall effect (QAHE) in SnTe.

Effect of strain on the magnetic states of transition-metal atoms doped monolayer WS2

The effects of transition-metal atoms doping and elastic strain on the magnetic properties of monolayer WS2 are investigated by the first-principles calculation. Firstly, we investigate the magnetic properties of a series of 3d transition-metal atoms (from Sc to Zn) doped monolayer WS2. Our calculations show that doping of transition-metal atoms from Sc to Cr results in nonmagnetic states, while Mn, Fe, Co, Ni, Cu and Zn doping can induce magnetism in WS2 monolayer. The localized nonbonding 3d electrons of TM atoms lead to the formation of magnetic moments. Meanwhile, our calculations indicate that the elastic strain can be used to manipulate the spin polarization of TM-3d orbital. Specifically, the magnetic moment of Fe and Co-doped monolayer WS2 increase with the increase of tensile strain, while the magnetic moment of Mn, Ni, Cu and Zn-doped WS2 monolayer initially increase and then decrease with the increase of tensile strain. On the other hand, the magnetic moment of Fe, Co, Mn, Ni, Cu and Zn-doped WS2 monolayers decrease with the increase of compressive strain. While the magnetic moment of Sc, Ti, V and Cr-doped WS2 monolayers remain 0μB independent of tensile strain and compressive strain.

Modulating electronic, magnetic and chemical properties of MoS2 monolayer sheets by substitutional doping with transition metals

Based on first-principles calculations, the effects of substitutional doping with transition-metal (TM) atoms (Co, Ni, Ru, Rh, Pd, Ir, Pt and Au) were investigated on the electronic structure, magnetic property and chemical activity of the molybdenum disulfide (MoS2) monolayer sheet. It is found that all the considered TM atoms are strongly bonded to the sulfur defects. The magnetic properties of MoS2 monolayer sheets can be modulated by embedding TM atoms. The introduced spin magnetic moments are 1.00, 1.00, 1.00, 0.99, and 2.00μB, respectively, for Ir, Rh, Co, Au and Ru doping. The electronic properties of MoS2 monolayer sheets are also significantly changed due to the induced impurity states in the band gap. The chemical activity of the TM-doped MoS2 monolayer sheet (TM-MoS2) is significantly enhanced compared with the undoped sheet. Most TM-MoS2 can strongly adsorb and thus effectively activate the adsorbed O2. It is proposed that the partially occupied d orbitals of the doped TM atoms localized in the vicinity of the Fermi level play a crucial role in adsorbing and activating the adsorbed O2. The adsorption of O2 can in turn modify the electronic structures and magnetic properties of TM-MoS2.

Influence of transition metal atoms doping on structural, electronic and nonlinear optical properties of Mg12O12 nanoclusters: A DFT study

Using density functional theory, we investigated the effect of transition metal doping on structural, electronic, energetic, linear and nonlinear optical properties of Mg12O12 nanocluster. The result revealed that transition metal atoms doping lead to reduce the Eg and increase the dipole moment. The doping of transition metal atom on Mg12O12 nanocluster enhances its polarizability value. Also polarizability values for doped nanoclusters decrease as the atomic number of transition metal increase. The first hyperpolarizability value dramatically increases as substitute a magnesium atom with a transition metal atom. Among the transition metal atom doped nanocage, scandium has the largest first hyperpolarizability value (β◦≈47,872au). The stability and remarkable values of β◦ (for Sc, Ti and V doped of nanocage) suggest that these compounds may be applicable as NLO material in industrial.

The Dilute Magnetic Properties of Monolayer MoS<sub>2</sub> Doped with Transition Metal Fe and VA Atoms

The two-dimensional material MoS2 has attracted a growing attention due to its potential applications in electronic devices in recent years [1,2,3], and the monolayer MoS2 is a direct gap semiconductor with a band gap of 1.8eV [4]. In the existing studies, it has indicated that MoS2 can get an available magnetism with doping transition metal atoms [5], and is expected to be a new generation of diluted magnetic semiconductor (DMS) [6,7]. Moreover, we found that Fe-doped MoS2 could present a strong magnetism but a semimetal characteristic, losing its original semiconductor properties while obtaining magnetism. Therefore, it is necessary to explore some methods to make monolayer MoS2 exhibit both magnetic and semiconductor properties. In this paper, we propose the method of N, Fe atoms co-doping to achieve this objective. The structural, electronic and magnetic properties of MoS2 doped with transition metal Fe and VA atoms have been investigated by first principle calculations based on density functional theory. The 3×3×1 supercell of monolayer MoS2 as a calculation model has been used. The result shows that pure MoS2 has no magnetism, while Fe-doped MoS2 exhibits a good magnetism about 1.849μB but a semimetal characteristic. This is due to that Mo-4d, S-2p, Fe-3d states has a strong coupling around the Femi energy for the introduction of Fe atom, and the Femi energy only pass through the spin-up density of states. For the co-doping with VA atoms and Fe atoms, it is found that the magnetic moment of Fe-N, Fe-P and Fe-As co-doped MoS2 is 0.956μB, 0.775μB, 0.782μB. Moreover, the Fe-N co-doped MoS2 presents semiconductor characteristics, in contrast, Fe-P and Fe-As co-doped MoS2 appear semimetal properties. It indicates that the semimetal characteristic of Fe-doped MoS2 could change into indirect band gap semiconductor due to the introduction of N atom. The band gap is 0.2eV. Our study demonstrate that the method of Fe, N co-doping could make MoS2 have good magnetic and also semiconductor properties at the same time.

Room-Temperature Ordered Spin Structures in Cluster-Assembled Single V@Si12 Sheets

Since most of the existing pristine two-dimensional (2D) materials are either intrinsically nonmagnetic or magnetic with small magnetic moment per unit cell and weak strength of magnetic coupling, introducing transition metal atoms in various nanosheets has been widely used for achieving a desired 2D magnetic material. However, the problem of surface clustering for the doped transition metal atoms is still challenging. Here we demonstrate via first-principles calculations that the recently experimentally characterized endohedral silicon cage V@Si12 clusters can construct two types of single cluster sheets exhibiting hexagonal porous or honeycomb-like framework with regularly and separately distributed V atoms. For the ground state of these two sheets, the preferred magnetic coupling is found to be ferromagnetic due to a free-electron-mediated mechanism. By using external strain, the magnetic moments and strength of magnetic coupling for these two sheets can be deliberately tuned, which would be propitious to their advanced applications. More attractively, our first-principles molecular dynamics simulations show that both the structure and strength of ferromagnetic coupling for the pristine porous sheet are stable enough to survive at room temperature. The insights obtained in this work highlight a new avenue to achieve 2D silicon-based spintronics nanomaterials.

Improved Electron/Li-Ion Transport and Oxygen Stability of Mo-Doped Li2MnO3

Li2MnO3 plays significant roles in stabilizing the structure and ensuring a high specific lithium storage capacity of the Li-rich layered xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn, etc.) composites (or solid solutions) as cathode materials for lithium ion batteries (LIBs)1. Nevertheless, it meets challenges in irreversible structural transition and low coulombic efficiency due to the loss of oxygen in the initial charge process. In addition, its insulating property deteriorates the rate performance of the xLi2MnO3·(1-x)LiMO2. These drawbacks hinder the commercialization and application of the composites as cathode materials for LIBs. Elemental substitution or atom doping has been commonly applied to improve the electrochemical performances of Li2MnO3 2-4. In an electrochemical viewpoint, as Mn4+ cannot be further oxidized in octahedral coordination in the pristine Li2MnO3, the charge compensation has to be conducted by the oxidation of the O2- ions alone upon Li-ion extraction, leading to irreversible structural change and safety issues. In contrast, as Mo4+ is potentially oxidized to Mo6+, the charge compensation will be largely declined from oxygen if multi-electron transfer occurs on the doped transition metal atoms in Li2Mn1-x Mo x O3. Therefore, substituting Mn with Mo is expected to reduce the loss of oxygen and improve the stability of the structure. In addition, considering the difference of Li2MnO3 (red) and its iso-structured Li2MoO3 (black) in color, Mo substitution for Mn might also improve the conductivity and rate performance of Li2MnO3and its related cathode materials. In this work, first-principles calculations are conducted to predict the impacts of molybdenum (Mo) doping on the physical and electrochemical properties of Li2MnO3. It demonstrates that Mo doping is indeed beneficial in improving both the dynamic and thermodynamic properties of Li2MnO3: (1) It decreases the band gap and increases the number of states around the Fermi level; (2) It enhances Li-ion diffusion especially between the lithium layer and the transition-metal layer; (3) Extra charge is transferred from Mo to O, accompanied with the reduction of the delithiation potential; (4) The charge of the removed Li-ion is compensated by both Mo and O in the Mo-doped Li2MnO3 during delithiation, and (5) Mo doping delays oxygen release and reinforces the stability of the structural oxygen based on the calculated reaction enthalpy. Therefore, Mo doping is expected to be an effective way in improving the structural stability and rate performance of Li2MnO3 and xLi2MnO3·(1-x)LiMO2 cathode materials. These findings will facilitate the investigation and promote the development of Li2MnO3 and xLi2MnO3·(1-x)LiMO2 cathode materials. M. M. Thackeray, S.-H. Kang, C. S. Johnson, J. T. Vaughey, R. Benedek and S. A. Hackney, J. Mater. Chem., 17, 3112-3125 (2007).M. Tabuchi, Y. Nabeshima, K. Ado, M. Shikano, H. Kageyama and K. Tatsumi, J. Power Sources, 174, 554-559 (2007).D. Mori, H. Sakaebe, M. Shikano, H. Kojitani, K. Tatsumi and Y. Inaguma, J. Power Sources, 196, 6934-6938 (2011).S. Kim, J.-K. Noh, S. Yu, W. Chang, K. Y. Chung and B.-W. Cho, J. Electroceram., 30, 159-165 (2013).

Density functional study of transition-metal-encapsulated Si10C10H20 cage-like clusters

Using the density functional theory with generalized gradient approximation, we have studied the geometries, stabilities, and electronic and magnetic properties of 3d transition-metal (TM)-encapsulated hydrogenated Si10C10H20 cage-like clusters. The hydrogenated empty Si10C10H20 cage is very stable with large highest-occupied–lowest-unoccupied molecular orbital (HOMO–LUMO) gap. Endohedral doping of the empty cage with different 3d TM atoms shows that doping can be used to manipulate the HOMO–LUMO gap of the cage. Most interestingly, the TM-doped Si10C10H20 cage can conserve the high spin moment of the TM atom due to weak interaction between the TM atom and the cage. The electronic properties of TM-doped Si10C10H20 cages are characterized by electron transfer from the host empty Si10C10H20 cage to the guest doping TM atoms. First-principles molecular dynamics simulations have shown that the TM-doped Si10C10H20 cages have good thermal stability.

Prediction of two-dimensional diluted magnetic semiconductors: Doped monolayer MoS2systems

Using first-principles calculations, we propose a two-dimensional diluted magnetic semiconductor: monolayer MoS${}_{2}$ doped by transition metals. Doping of transition metal atoms from the IIIB to VIB groups results in nonmagnetic states, since the number of valence electrons is smaller or equal to that of Mo. Doping of atoms from the VIIB to IIB groups becomes energetically less and less favorable. Magnetism is observed for Mn, Fe, Co, Zn, Cd, and Hg doping, while for the other dopants from these groups it is suppressed by Jahn-Teller distortions. Analysis of the binding energies and magnetic properties indicates that (Mo,$X$)S${}_{2}$ ($X=\text{Mn}$, Fe, Co, and Zn) are promising systems to explore two-dimensional diluted magnetic semiconductors.

The structural, electronic and magnetic properties of bi-layered MoS2 with transition-metals doped in the interlayer

We have carried out first-principles calculations and theoretical analysis to explore the structural, spin-polarized electronic and magnetic properties of bi-layered MoS2 with transition-metal (TM) atoms (Cr, Mn, Fe, Co and Ni) doped in the interlayer. The charge density distribution indicates that the doping TM atoms and the nearest S atoms in the lower and upper planes display a clear covalent-bonding feature. The local moments of the doping TM atoms are smaller than the magnetic moments of their free states. Also, the spin polarization is found to be 100% at the Fermi level or HOMO level for interlayer doping with Cr, Mn, Fe and Co.

Density functional calculations of geomatric structure, electronic structure, stability, and magnetic properties of transitional atom endohedral unclassical fullerene M@C22(M=Sc,Ti, V, Cr, Mn, Fe, Co and Ni)

The generalized gradient approximation (GGA) based on density functional theory(DFT) is used to analyze the structural and electronic properties of the unclassical endohedral fullerene M@C22(M=Sc, Ti, V, Cr, Mn, Fe, Co and Ni). It is found that the ground-state structure of the unclassical fullerene C22 is a spin singlet cage containing one four-membered ring and the doping of transition metal atom can obviously enhance the stability. It is discovered that the C-M bond have both the covalent and the ionic characteristics. The analyses of magnetism, energy levels, orbital wave functions and density of states show the hybridization between the 3d orbital ofM atom and the C atomic orbital in C22. In addition, Ti, Cr, Fe and Ni atoms become non-magnetic after they have been doped into the C22.

Substitutional doping of BN nanotube by transition metal: A density functional theory simulation

Substitution of all 10 3d transition metal (TM) atoms in a [8, 0] zigzag single walled boron nitride nanotube (BNNT) has been investigated with density functional theory based methods. The TM atoms protrude to the exterior of the wall and may facilitate this site to react with an approaching molecular or atomic species. The substitution is site selective when the number of d electrons is less than five with major product of B-substituted BNNT. The substitution produces mixture of B- and N-substituted BNNT when the number of d electrons is larger than five. The doping of TM atoms induces certain impurity states within the band gap of the pristine BNNT, thereby reducing the band gap and affecting the conductivity of metal-doped BNNTs.

Stability and magnetic properties of transition metal atoms endohedral BnNn (n=12–28) cages

First-principles calculations have been conducted to systemically investigate the stability and magnetic properties of 3d and 4d transitional-metal (TM) atoms doped in the BnNn (n=12,16,20,24,28) cages. Among those cages, the B24N24 is the optimal one for encapsulating 3d and 4d TM atoms according to the computed heat of formation. Inside B24N24 cage, 3d and 4d TM dopants belonging to the same group in the Periodic Table exhibit similar magnetic behaviors. Most of the 3d and 4d TM atoms remain magnetic after doped in the B24N24 cage except for Ni, Zr, and Pd. The magnitudes of the remaining moments for 3d (except for Sc, Ti, and V) and 4d dopants are reduced from those of free atoms. The energy gaps are localized at the doped transition metal atoms. Encapsulations of two TM atoms inside the B24N24 cage were also considered.

Magnetic properties of transition metal atoms doped in silicon nanotubes with hexagonal prism structure

Magnetic properties of magnetic transition metals doped in the infinite Si nanotubes (SiNTs) with hexagonal prism structure (Si/sub 12/M/sub n/, M=Fe, Co, Ni, n=1, 2) have been investigated for two different numbers of dopants per hexagonal prism by using the localized basis calculational method. The decrease (increase) of spin-down (spin-up) electrons for the n=2 case results in the increase of magnetic moments compared with the n=1 case. The calculated magnetic moment per dopant Fe atom (2.39 /spl mu//sub B/) is larger than both of the bulk value (2.22 /spl mu//sub B/) and previous result for finite nanotube (1.7 /spl mu//sub B/). For Co and Ni atoms doped in the tube, the magnetic moments are smaller than those of bulk metals. The Si-Si bond lengths for the hexagonal prisms decrease compared with that of the nanotube without transition metals, but there is no dependency on different dopants. The distances between the transition metals and Si atoms decrease as the atomic number of transition metals increases, which is the same trend for the atomic radii of transition metal atoms. The doping of transition metal atoms leads to the increase of the binding energy (BE).