3d Transition Metal Atoms Research Articles

Ferroelectric control of magnetism of 3d transition metal-adsorbed graphene monolayers

Electric control of magnetism has significant application prospect in magnetic storage. In this work, first-principles calculations are carried out to study the ferroelectric control of magnetism of the 3d transition metal (TM = V, Cr, Mn, Fe, Co, or Ni)-adsorbed graphene monolayers by using an organic ferroelectric poly(vinylidene-fluoride) (PVDF). Although we observe the ferroelectric control of the magnetocrystalline anisotropy energy (MAE) of all the studied 3d transition metal atoms, the flip of the easy magnetization axis is only achieved in the case of Ni adsorption. When the Ni atom is adsorbed at the bridge site on the graphene monolayer, the easy axis of magnetization would undergo a transition from out-of-plane (MAE = 0.07 meV/atom) to in-plane (MAE = −0.23 meV/atom) when the polarization turns down to up. As a result, the study of Ni is particularly highlighted, and the underlying mechanism is discussed by second-order perturbation theories. We provide a means to realize electric control of the magnetism of graphene, which will facilitate relevant experimental and theoretical research.

Magnetism in single-layer of Zrse[formula omitted] by substituting 3[formula omitted] transition metals for Zr: Structural symmetry versus exchange splitting

To understand the magnetic properties of the novel two-dimensional materials and other phenomena which depend on electron correlation, finding the states located around Fermi energy (EF) and contributing to the correlated states of the system is basically important. In this paper, using the density functional theory, we investigate the electronic properties of substitution of 3d transition metal (TM) atoms for Zr in trigonal prismatic 2H and octahedral 1T structure of monolayer TM-doped ZrSe2 materials. The band structure, orbital projected density of states (DOS), and the number of electrons in the d-shell show that the correlated subspace depends strongly on the structural phase of the systems. The case of Mn substitution has the highest magnetic moment, 2.91 μB and 3.30 μB in 2H and 1T phases, respectively. In the 1T structure of Mn-doped ZrSe2, almost partially filled t2g impurity bands is well separated from eg states in the non-magnetic calculation, having a small bandwidth of about Wb= 0.4 eV. As a consequence, the strength of electron correlation U/Wb increases (U is effective on-site Coulomb interaction) and puts this compound in the moderately or strongly correlated regime, and causes a stronger electron spin separation than the 2H phase. In the 2H phase, the correlated states include two impurity bands with dominantly dxy and dx2−y2 characters and induce a smaller magnetic moment. Due to the large DOS of Mn and Cr atoms at the EF in both 1T and 2H structures, the Stoner criterion I.D(EF)>1 is satisfied, which is reasonably consistent with our results of ferromagnetic total energy calculations and the sizable magnetic moments.

Nitrogen atom coordination tuned transition metal catalysts for NO oxidation and reduction

Developing an efficient catalyst for NO oxidation and reduction at ambient temperature is a significant challenge. Recent studies have suggested that the N-coordinated transition metal (TM) single atom catalysts (SACs) have high catalytic activity and stability. Herein, we report the activation potential of a series of 3d TM atoms supported on N coordination-tuned graphene (GR) for NO oxidation and reduction. The results show that the N coordination pattern can greatly alter the catalytic reactivity of TM on the catalysts, and the TM atom on the catalysts with three-coordinated pyridinic nitrogen TM-N3@GR exhibit the strongest chemical activity. Among the TM-N3@GR catalysts, Ti–N3@GR is the most promising candidate. The rate constants and equilibrium constants were calculated to evaluate the kinetic and thermodynamic feasibility of the catalytic reaction, respectively. Our results demonstrate that the reduction of NO to N2 on Ti–N3@GR can occur at ambient temperature with a large exotherm of 6.99 eV, and the oxidation of NO to NO2 on Ti–N3@GR can easily proceed when the temperature reaches 360 K with a large equilibrium constant. Our studies are of great significance for understanding the performance of N coordination-tuned catalysts and designing Ti-based catalysts for NO oxidation and reduction.

Insight into the origin of magnetism in 3d transition-metal atoms doped PC6: A first-principles study

The effect of 3d transition-metal (TM) atoms (Sc–Ni) substitutional doping on the structural, electronic and magnetic characters of PC6 ([email protected]6) is systemically investigated by first-principles calculations in the framework of density functional theory. Our calculations show that introducing of V, Cr, Mn and Fe atoms makes the original non-magnetic PC6 changing into ferro-magnetic, while Sc, Ti, Co and Ni atoms substitutional doped PC6 are still non-magnetic. The magnetic behavior can be qualitatively interpreted by a simple model, which associated with hybridization between the 3d orbitals of TM atoms and the defect levels of unrelaxed D3h symmetrical P vacancy, i.e., hybridization model. The occupation of electrons in hybridized electronic levels determines whether the doping system is magnetic: when the bonding levels (for [email protected]6 and [email protected]6), the nonbonding levels and antibonding levels (for [email protected]6 and [email protected]6) are fully occupied, the corresponding doping systems have no magnetic, while when the nonbonding levels and the antibonding levels (for [email protected]6, [email protected]6, [email protected]6 and [email protected]6) become partially filled, these systems exhibit localized spin moments of 1–3 μB. The results are helpful to understand the origin of magnetism in [email protected]6 and provide a theoretical basis for potential applications in spintronic devices.

Magnetic properties and electronic structure of 3d transition-metal atom adsorbed two-dimensional SnSe2

Two-dimensional materials have attracted widespread interest in the field of spintronics due to their unique electronic structure and properties. Monolayer SnSe2 has been widely used in thermoelectric and optoelectronic applications, but its application for spintronics is limited by its inherent lack of magnetic properties. Tuning the electronic structure and magnetic properties of two-dimensional materials (TDMs) by introducing transition metal elements (TM) to be applicable in the field of spintronic devices is a common means of accomplishing this. The electronic structure and magnetic characteristics of 3d TM adsorbed with two-dimensional SnSe2 are predicted by first-principles calculations. The value of the magnetic moments from 0.16 to 4.07 μB in the adsorption systems, reaching a maximum in the case of Mn atom adsorption. The case of Ti atom adsorption has the maximum value of MAE in [001] direction. These results have shown that TM adsorbed 2D SnSe2 have prospective applications in spintronic devices.

Spin and orbital magnetism of exohedral fullerene doped with single transition metal atom (Sc-Ni): A relativistic density functional theory study

Relativistic density functional theory calculations have been implemented to study the structural configurations, electronic and magnetic properties of exohedral 3d transition metal atoms doping on C60 fullerene (TM-C60) by a full potential local orbital method. The calculated binding energies revealed that the TM-C60 molecules are energetically stable in all adsorption sites. We also found that the TM-doped exohedral C60 complexes are more reactive than pure C60 fullerene. The spin and orbital magnetic moments were also determined. We have indicated that in all of the five adsorption sites, exohedral TM-C60 molecules (except for Ni-C60) are magnetized. Our magnetic calculations show that the total spin magnetic moments of TM-C60 molecules mainly come from the TM atoms. We found that the spin magnetic moments of adsorbed TM atoms in exohedral doping C60 fullerene from Sc to Mn (HH adsorption site) and for Sc to Cr (HP and P adsorption sites) are greater than their free states. Our calculations suggest that exohedral doping 3d TM-C60 complexes can almost maintain spin magnetic moments. We have indicated that the magnetic properties of exohedral TM-C60 molecules change in the presence of spin–orbit coupling. Significant orbital contributions to magnetic moments are recognized in these configurations while the spin moments are unaffected. We found that Co in exohedral doping of C60 fullerene shows a robust orbital moment in all the five adsorption sites.

Screening of transition metal doped two-dimensional C2N (TM-C2N) as high-performance catalyst for the non-oxidative propane dehydrogenation

Since last decade, single atom catalysts have massive development in the field of propane dehydrogenation (PDH). In this study, both the catalytic activity and reaction mechanism of 3d, 4d, and 5d transition metal atom anchored on C2N (TM-C2N) for non-oxidative PDH are studied in detail using the density functional theory methods. Firstly, six stable catalysts (Cr-, Mn-, Fe-, Co-, Cu-, and Ag-C2N) are screened out by calculating the difference between the formation energy of the single atom and the cohesive energy of the corresponding bulk metal. Combining the results of adsorption energy and density of states, it is demonstrated that propane and propylene can be stably adsorbed on all screened TM-C2N. The calculated activation barrier and reaction energy of elementary reactions involved in PDH indicate that the initial C−H bond breaking step is determined as the rate-determining step on almost all the screened TM-C2N catalysts. Among all studied TM-C2N, the Fe-C2N possesses excellent catalytic activity even better than other promising catalysts. In addition, the d-band center values of transition metal atoms in screened TM-C2N show a stronger liner relationship with the interaction energy, suggesting that the d-band center may be served as a priority descriptor for the interaction energy between reaction species and catalyst surface rather than for the adsorption energy of reaction species.

Effects of 3d transition metal impurities and vacancy defects on electronic and magnetic properties of pentagonal Pd2S4: competition between exchange splitting and crystal fields

In this paper, we first investigate the electronic properties of the two-dimensional structure of dichalcogenide Pd2S4. These properties strongly depend on the crystal field splitting which can change by atomic vacancies (S and Pd vacancies). The main purpose of the present paper is to create remarkable magnetic properties in the system by adding 3d transition metal atoms where the presence of Mn, Cr, and Fe creates the exchange interaction in the system as well as change in the crystal field. The created magnetic properties strongly depend on the competition between exchange interaction and crystal field to separate the levels of d orbitals. In addition, the presence of the transition metals in the structures with S and Pd vacancy has been investigated carefully. The calculations demonstrate that we can achieve an extensive range of magnetic moment up to 3.131 {mu }_{B}. The maximum one is obtained in the presence of Mn and absence of sulfur while some of the doped structures does not have magnetic moment. Our results show that Pd vacancy in the presence of Cr, Mn and Fe metals increases the magnetic property of the Pd2S4 structure. The extensiveness and variety of the obtained properties can be used for different magnetic and non-magnetic applications.

Role of spin-resolved anti-bonding states filling for enhanced HER performance in 3d transition metals doped monolayer WSe2

Transition metal dichalcogenide monolayers are an emerging family of electrocatalysts, in which Tungsten diselenide (WSe2) has attracted attention for Hydrogen evolution reaction (HER). Here, the magnetism and HER performance of 3d transition metal atoms doping WSe2 (TM-WSe2) are comprehensively studied using density functional theory. The hybridization between the localized TM-3d and the delocalized Se-4p or W-5d states leads to the ferromagnetic/antiferromagnetic coupling between the TM spins and Se or W spins, which induces magnetism in WSe2. With the analysis of the integrated-crystal orbital Hamilton population (ICOHP), the ICOHPspin up values of TM-WSe2 are decreased compared to the pure WSe2, which improves the interaction of Se-H, thereby the H atom is easier to be adsorbed on the Se1 site. While all the ICOHPspin down values of TM-WSe2 are increased, this indicates the weak interaction of Se-H, which promotes the desorption of H2 molecule. Thus, the synergistic effect of spin up and spin down anti-bonding states filling makes TM-WSe2 possess an enhanced HER performance. Moreover, the Ni/Cu-WSe2 possesses optimal HER performance with lower ΔGH* (-0.20 and 0.06 eV). Therefore, our results provide a primary understanding for the relationship between the spin up/down anti-bonding states filling and HER electrocatalytic performance.

Density functional theory study of N2 adsorption and dissociation on 3d transition metal atoms doped Ir(1 0 0) surface

Ammonia is among the chemicals that are produced in large amounts worldwide and therefore play an important role in global economy. Recently, the electrocatalytic nitrogen reduction reaction (NRR) has attracted significant research attention as the most promising technology for ammonia synthesis. Therefore, designing an efficient electrocatalyst is a crucial issue that needs to be addressed. In this study, using density functional theory calculations, we designed a series of electrocatalysts containing 3d transition metal (TM = Ti–Zn) atoms doped on Ir(100) surface (TM@Ir(100)) and studied the effect of TM@Ir(100) on N2 adsorption, activation, and dissociation. The doping of TM atoms regulated the electronic structure of Ir(100) and promoted its catalytic activity. TM@Ir(100) (TM = Ti, V, Cr, Mn, Fe, and Co) effectively activated N2, and the N–N bond was elongated to ∼ 1.290 Å. The doping of TM atoms promoted charge transfer between N2 and TM@Ir(100) and activated the N≡N bond, affording high catalytic activity. Furthermore, the dissociation behavior of N2 on TM@Ir(100) was investigated. Mn@Ir(100) exhibited the highest catalytic activity and a low energy barrier for N2 dissociation (0.598 eV), making it a potential NRR electrocatalyst.

Tuning the activity and selectivity of nitrogen reduction reaction on double-atom catalysts by B doping: A density functional theory study

Electrocatalytic reduction of nitrogen is a simple, green and sustainable method for the production of NH3, so it is very necessary to find an efficient and low-cost electrocatalyst. Here, we systematically studied the catalytic performance of two 3d transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) atoms loaded on C2N monolayer. Through density functional theory calculations and systematic theoretical screening, it is known that Sc and Ti loaded structures can undergo nitrogen reduction reactions (NRR). Unfortunately, the limiting potential (UL) of NRR is not very friendly and is not conducive to the production of NH3. In order to reduce the UL of NRR, we further studied the structure of B and Ti co-doping (B-Ti2 @C2N). As expected, the UL of the B-Ti2 @C2N via the consecutive pathway is 0.10 eV, with high electrocatalytic activity, which effectively inhibiting the competition of the hydrogen evolution reaction. This theoretical research not only adds a new member to the family of electrocatalysts for nitrogen fixation, but also further increases our physical insights on adjusting catalytic activity, which is expected to guide the rational design of improving the catalyst activity of NRR.

Electronic structures and magnetic properties of 3d transition metal doped monolayer RhI3

Two dimensional (2D) magnetic semiconductor CrI3 and Cr2Ge2Te6 have attracted great concern in the past five years. However, their low stability and low Curie temperatures greatly limit their application in spintronic devices. Here, we report the doping effects of 3d transition metal on the electronic and magnetic properties of monolayer RhI3, a newly synthesized 2D semiconductor with excellent structural stability. Our first-principles calculations show that the 3d transition metal atoms can significantly change the electronic structures of monolayer RhI3. For example, Sc- and Co-doped monolayers are non-magnetic semiconductors, Ni-doped monolayer is half metallicity, and Ti-, V-, Cr-, Mn-, Fe-, Cu-, and Zn-doped monolayers are magnetic semiconductors. These differences can be understood from the energy splitting induced by crystal field theory and the strong correlation effect between 3d electrons. Our work proposes that the 3d transition metal atoms doped RhI3 are novel dilute magnetic semiconductors.

Tuning the magnetic and electronic properties of MoI3 monolayer by 3d transition metal doping: A first-principles study

Two-dimensional (2D) materials with intrinsic magnetism have sparked a lot of attention due to their potential applications in spintronics. Recently, monolayer molybdenum triiodide (MoI3), which is a member of the transition metal trihalides (MX3) family, has been predicted to be a stable bipolar ferromagnetic semiconductor (BFMS) with intrinsic magnetism. By means of first-principle calculations based on the GGA + Ueff approach, we modified MoI3 through substitutional doping with 3d transition metal (TM) atoms to improve its spintronic properties. We focused on the study of structural, electronic and magnetic properties of the pristine and 3d TM (TM = Sc, Ti, V, Cr, and Mn) doped MoI3 systems. Our findings reveal that substitutional doping of MoI3 monolayers with Sc and Ti atoms changes their electronic character from a BFMS to a ferromagnetic semiconductor, while V- and Cr-doped MoI3 monolayers result in half semiconducting properties (HSC). More interestingly, the Mn-doped MoI3 monolayer reveals a half-metallic character with enhanced magnetism and sustains these properties even under spin–orbit coupling (SOC). In addition, robust ferromagnetism and high mean-field Curie temperatures were found in all doped systems, especially in the V-doped MoI3 monolayer. By exhibiting these unique electronic and magnetic properties, these TM-doped MoI3 systems could serve as potential candidates for spintronic applications.

DFT investigation of Au9M2+ nanoclusters (M = Sc-Ni): The magnetic superatomic behavior of Au9Cr2+

Au102+ has been found very stable showing a superatomic behavior with a highly symmetrical geometry and can be considered as the smallest copy of the golden pyramid Au20. In this work, we further explore superatomic clusters as analogues of more complex molecules by doping Au102+ cluster with 3d transition metal atom. It is found that, in similarity to their sister Au19M, the structural evolution of Au9M2+ is ruled by the bond strength of AuM dimers and can be generalized into two motifs: the endohedrally doped cage-like structure for lighter dopants (M = Sc and Ti) and the slightly distorted tetrahedral structure for heavier ones. The average binding energies and dissociation energies are calculated to identify the relatively stable patterns. The molecular orbital (MO) diagram as well as the spin distribution are computed to understand the electronic structure and magnetic behavior of studied clusters. The spin magnetic moments of Au9M2+ clusters systematically vary from 0 to 5 μB, depending on the localization of unpaired 3d electrons. With a large spin magnetic moment of 5 μB, the exceptionally stable Au9Cr2+ is identified as a potential magnetic superatom and would be beneficial for further theoretical and experimental studies.

Doping of 3d Transition Metals o n Monolayer o f Graphene a nd Borophene

We Study the doping of various metallic 3d transition metal (TM) atoms like iron (Fe), Cobalt (Co), Copper (Cu) and Nickel (Ni) on monolayer of the borophene and graphene. These 2D layers show energy dispersion and metalloid properties because its band gap is very less or near to zero. We explored borophene is semi-metallic with the titled Dirac cone and graphene is semi metallic whose conduction and valence bands meets at Dirac cone. We analyzed the adsorption of 3d transition metal (TM) on the 2D layers through density functional theory (DFT) based calculations. In this paper, we observed the most suitable and acceptable adsorption site for each adatom, and calculated the binding energy per atom, density of states and magnetic moment of resulting borophene and graphene-adatom system. Here, we find that Nickel (Ni) is perfect as electron doping and iron (Fe) is the most effective for magnetically doped borophene. In the case of graphene we find that Co is most suitable for magnetically doping and Cu is best for electron doping.

High Accuracy Transition Metal Effective Cores for the Many-Body Diffusion Monte Carlo Method.

Practical applications of the real-space diffusion Monte Carlo (DMC) method require the removal of core electrons, where currently localization approximations of semilocal potentials are generally used in the projector. Accurate calculations of complex solids and large molecules demand minimizing the impact of approximated atomic cores. Prior works have shown that the errors from such approximations can be sizable in both finite and periodic systems. In this work, we show that a class of differential pseudopotentials, known as pseudo-Hamiltonians, can be constructed for the 3d transition metal atoms, entirely removing the need for any localization scheme in the DMC projector. As a proof of principle, we demonstrate the approach for the case of Co. In order to minimize errors in the pseudo-Hamiltonian at the many-body level, we generalize the recently proposed correlation-consistent pseudopotential generation scheme to successively close semilocal representations of the differential potentials. Our generation scheme successfully produces potentials tailored specifically for real space projector quantum Monte Carlo methods with low error at the many-body level, i.e., with many-body scattering properties very close to relativistic all-electron results. In particular, we show that the agreement with respect to atomic and molecular quantities reach chemical accuracy in many cases─on par with the most accurate semilocal pseudopotentials available. Further, our pseudo-Hamiltonian generation scheme utilizes standard quantum chemistry codes designed only to work with semilocal pseudopotentials, enabling straightforward generation of pseudo-Hamiltonians for additional elements in future works.

Coexistence of magnetism in SnX (X = S, Se, Te) monolayers by the adsorption of 3d transition-metal atoms

Magnetism can be induced in two-dimensional (2D) group IV monochalcogenide monolayers (MLs) by the decoration of transition-metal (TM) atoms. The induced magnetism in the group IV monochalcogenides enhances their potentiality in 2D spintronic devices, which has attracted extensive attention nowadays. In this context, the structural, electronic, and magnetic properties of transition metal atoms (Mn, Fe, Co) adsorbed SnX (X = S, Se, Te) MLs are investigated by using first-principles calculations. The TM atoms adsorbed SnX MLs are found to be energetically stable with the pnma space-group, and show the semiconducting nature with electronic band gaps in the range of 0.52–1.05 eV revealing the negligible spin–orbit coupling effect in most of the studied systems. The asymmetry between spin majority and spin minority channels is revealed in the electronic density of states of the adsorbed systems, which is mainly contributed by the hybridization of the 3d orbitals of TM atoms with the 4p and 4s orbitals of Sn and X atoms. Magnetic states are realized for SnX atoms in the adsorbed systems with the induced magnetic moments between −0.03 to −0.33 μB, which indicates the antiferromagnetic alignment between TM atoms and neighboring SnX atoms. Co adsorbed SnSe and Fe adsorbed SnTe MLs are found to have significant magneto-crystalline anisotropy energy values of 0.37 and 0.84 meV/TM atom, respectively, with the preferred perpendicular direction. In addition, the p-type doping is induced in the SnX MLs as indicated by the calculation of charge transfer between the adsorbed TM and SnX atoms. The results demonstrate potential applications of TM atoms adsorbed SnX MLs for spintronic and magnetic storage devices.

Electron counting in cationic and anionic silver clusters doped with a 3d transition-metal atom: endo- vs. exohedral geometry.

Electron counting is a concept that often governs properties of molecules, clusters, and complexes. Here we explore silver clusters doped with a transition-metal atom, where it has been an issue whether or not 3d electrons delocalize to participate in electron counting. The experiment is performed on AgNM+/- (M = Sc-Ni) clusters to examine their stability through chemical reactivity, enabling systematic control of the number of valence electrons by the cluster size, the charge state, and the transition-metal element across the periodic table. It is revealed for 18-valence-electron clusters that 3d electrons participate in electron counting to show exceptional stability only when the transition-metal atom is endohedrally doped, except for Cr and Mn doping that forces 3d electrons to localize. We thus present new entries for superatomic metal clusters as well as a geometric factor that regulates the behavior of 3d electrons in the nanoscale regime.

Theoretical study on exohedral complexes C6H6TMB40 (TM = Sc-Ni).

Exohedral borospherene complexes comprised of 3d transition metal (TM) atoms with borospherene B40 and benzene (C6H6) molecules, C6H6TMB40, were systematically studied by using density functional theory (DFT). Results show that in the ground states, the bonding type between TM and B40 changes from η7 (TM = Sc-V) to η6 (TM = Cr-Fe) and then to η7 (TM = Co, Ni) with the increasing number of d electrons. Except for C6H6TiB40 and C6H6FeB40 being triplets, all C6H6TMB40 clusters have the lowest spin. Namely, the ground spin state with an even number of electrons is a singlet state, and the ground spin state with an odd number of electrons is a doublet state. The investigated C6H6TMB40 clusters (TM = Sc-Ni) possess higher stabilities through the ionic-covalent interactions between transition metals, benzene and the B40 cage.

First-row transition metal doped germanium clusters Ge16M: some remarkable superhalogens.

A theoretical study of geometric and electronic structures, stability and magnetic properties of both neutral and anionic Ge16M0/− clusters with M being a first-row 3d transition metal atom, is performed using quantum chemical approaches. Both the isoelectronic Ge16Sc− anion and neutral Ge16Ti that have a perfect Frank–Kasper tetrahedral Td shape and an electron shell filled with 68 valence electrons, emerge as magic clusters with an enhanced thermodynamic stability. The latter can be rationalized by the simple Jellium model. Geometric distortions from the Frank–Kasper tetrahedron of Ge16M having more or less than 68 valence electrons can be understood by a Jahn–Teller effect. Remarkably, DFT calculations reveal that both neutral Ge16Sc and Ge16Cu can be considered as superhalogens as their electron affinities (≥3.6 eV) exceed the value of the halogen atoms and even that of icosahedral Al13. A detailed view of the magnetic behavior of Ge16M0/− clusters shows that the magnetic moments of the atomic metals remain large even when they are quenched upon doping. When M goes from Sc to Zn, the total spin magnetic moment of Ge16M0/− increases steadily and reaches the maximum value of 3 μB with M = Mn before decreasing towards the end of the first-row 3d block metals. Furthermore, the IR spectra of some tetrahedral Ge16M are also predicted.