Photothermal catalytic C-C coupling to ethylene from CO_(2) with high efficiency by synergistic cooperation of oxygen vacancy and half-metallic WTe_(2)

Photothermal catalytic CO_(2) conversion provides an effective solution targeting carbon neutrality by synergistic utilization of photon and heat.However,the C-C coupling initiated by photothermal catalysis is still a big challenge.Herein,a three-dimensional(3D)hierarchical W_(18)O_(49)/WTe_(2) hollow nanosphere is constructed through in-situ embodying of oxygen vacancy and tellurium on the scaffold of WO_(3).The light absorption towards near-infrared spectral region and CO_(2) adsorption are enhanced by the formation of half-metal WTe_(2) and the unique hierarchical hollow architecture.Combining with the generation of oxygen vacancy with strengthened CO_(2) capture,the photothermal effect on the samples can be sufficiently exploited for activating the CO_(2) molecules.In particular,the close contact between W_(18)O_(49)and WTe_(2) largely promotes the photoinduced charge separation and mass transfer,and thus the~*CHO intermediate formation and fixedness are facilitated.As a result,the C-C coupling can be evoked between tungsten and tellurium atoms on WTe_(2).The ethylene production by optimized W_(18)O_(49)/WTe_(2) reaches 147.6μmol g^(-1)with the selectivity of 80%.The in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)calculations are performed to unveil the presence and significance of aldehyde intermediate groups in C-C coupling.The half-metallic WTe_(2) cocatalyst proposes a new approach for efficient CO_(2) conversion with solar energy,and may especially create a new platform for the generation of multi-carbon products.

Magnetism in Carbon Nanoscrolls: Quasi-Half-Metals and Half-Metals in Pristine Hydrocarbons

A magnetic ground state is revealed for the first time in zigzag-edged carbon nanoscrolls(ZCNSs)from spin-unrestricted density functional theory calculations.Unlike their flat counterpart-zigzag-edged carbon nanoribbons,which are semiconductors with spin-degenerate electronic structure-ZCNSs show a variety of magnetic configurations,namely spin-selective semiconductors,metals,semimetals,quasi-half-metals,and half-metals.To the best of our knowledge,this is the first discovery of quasi-half-metals and half-metals in a pure hydrocarbon without resort to an external electric field.In addition,we calculated the spin-dependent transportation of the semiconducting ZCNSs with 12 and 20 zigzag chains,and found that they are 13% and 17% at the Fermi level,respectively,suggesting that ZCNS can be an effective spin filter.

Prediction of one-dimensional CrN nanostructure as a promising ferromagnetic half-metal

Searching for one-dimensional(1D)nanostructure with ferromagnetic(FM)half-metallicity is of significance for the development of miniature spintronic devices.Here,based on the first-principles calculations,we propose that the 1D CrN nanostructure is a FM half-metal,which can generate the fully spin-polarized current.The ab initio molecular dynamic simulation and the phonon spectrum calculation demonstrate that the 1D CrN nanostructure is thermodynamically stable.The partially occupied Cr-d orbitals endow the nanostructure with FM half-metallicity,in which the half-metallic gap(?s)reaches up to 1.58 eV.The ferromagnetism in the nanostructure is attributed to the superexchange interaction between the magnetic Cr atoms,and a sizable magnetocrystalline anisotropy energy(MAE)is obtained.Moreover,the transverse stretching of nanostructure can effectively modulate?s and MAE,accompanied by the preservation of half-metallicity.A nanocable is designed by encapsulating the CrN nanostructure with a BN nanotube,and the intriguing magnetic and electronic properties of the nanostructure are retained.These novel characteristics render the 1D CrN nanostructure as a compelling candidate for exploiting high-performance spintronic devices.

Controllable high Curie temperature through 5d transition metal atom doping in CrI_(3)

Two-dimensional(2D) CrI_(3) is a ferromagnetic semiconductor with potential for applications in spintronics. However,its low Curie temperature(T_(c)) hinders realistic applications of CrI3. Based on first-principles calculations, 5d transition metal(TM) atom doping of CrI_(3)(TM@CrI_(3)) is a universally effective way to increase T_(c), which stems from the increased magnetic moment induced by doping with TM atoms. T_(c) of W@CrI_(3) reaches 254 K, nearly six times higher than that of the host CrI_(3). When the doping concentration of W atoms is increased to above 5.9%, W@CrI_(3) shows room-temperature ferromagnetism. Intriguingly, the large magnetic anisotropy energy of W@CrI_(3) can stabilize the long-range ferromagnetic order. Moreover, TM@CrI_(3) has a strong ferromagnetic stability. All TM@CrI_(3) change from a semiconductor to a halfmetal, except doping with Au atom. These results provide information relevant to potential applications of CrI_(3) monolayers in spintronics.

Half-metallicity induced by out-of-plane electric field on phosphorene nanoribbons

Exploring the half-metallic nanostructures with large band gap and high carrier mobility is a crucial solution for developing high-performance spintronic devices.The electric and magnetic properties of monolayer zigzag black-phosphorene nanoribbons(ZBPNRs)with various widths are analyzed by means of the first-principles calculations.Our results show that the magnetic ground state is dependent on the width of the nanoribbons.The ground state of narrow nanoribbons smaller than 8ZBPNRs prefers ferromagnetic order in the same edge but antiferromagnetic order between two opposite edges.In addition,we also calculate the electronic band dispersion,density of states and charge density difference of 8ZBPNRs under the action of out-of-plane electric field.More interesting,the addition of out-of-plane field can modulate antiferromagnetic semiconductor to the half metal by splitting the antiferromagnetic degeneracy.Our results propose a new approach to realize half-metal in phosphorene,which overcomes the drawbacks of graphene/silicene with negligible band gap as well as the transitional metal sulfide(TMS)with low carrier mobility.

Magnetic tuning in a novel half-metallic Ir_(2)TeI_(2) monolayer

A two-dimensional(2D) high-temperature ferromagnetic half-metal whose magnetic and electronic properties can be flexibly tuned is required for the application of new spintronics devices. In this paper, we predict a stable Ir_(2)TeI_(2) monolayer with half-metallicity by systematical first-principles calculations. Its ground state is found to exhibit inherent ferromagnetism and strong out-of-plane magnetic anisotropy of up to 1.024 meV per unit cell. The Curie temperature is estimated to be 293 K based on Monte Carlo simulation. Interestingly, a switch of magnetic axis between in-plane and out-of-plane is achievable under hole and electron doping, which allows for the effective control of spin injection/detection in such 2D systems. Furthermore, the employment of biaxial strain can realize the transition between ferromagnetic and antiferromagnetic states. These findings not only broaden the scope of 2D half-metal materials but they also provide an ideal platform for future applications of multifunctional spintronic devices.

Two-dimensional hexagonal Zn3Si2 monolayer:Dirac cone material and Dirac half-metallic manipulation

The fascinating Dirac cone in honeycomb graphene,which underlies many unique electronic properties,has inspired the vast endeavors on pursuing new two-dimensional(2D)Dirac materials.Based on the density functional theory method,a 2D material Zn3Si2 of honeycomb transition-metal silicide with intrinsic Dirac cones has been predicted.The Zn3Si2 monolayer is dynamically and thermodynamically stable under ambient conditions.Importantly,the Zn3Si2 monolayer is a room-temperature 2D Dirac material with a spin-orbit coupling energy gap of 1.2 meV,which has an intrinsic Dirac cone arising from the special hexagonal lattice structure.Hole doping leads to the spin polarization of the electron,which results in a Dirac half-metal feature with single-spin Dirac fermion.This novel stable 2D transition-metal-silicon-framework material holds promises for electronic device applications in spintronics.

Spin transport of half-metal Mn_(2)X_(3) with high Curie temperature:An ideal giant magnetoresistance device from electrical and thermal drives

Currently,magnetic storage devices are encountering the problem of achieving lightweight and high integration in mobile computing devices during the information age.As a result,there is a growing urgency for twodimensional half-metallic materials with a high Curie temperature(TC).This study presents a theoretical investigation of the fundamental electromagnetic properties of the monolayer hexagonal lattice of Mn_(2)X_(3)(X=S,Se,Te).Additionally,the potential application of Mn_(2)X_(3) as magneto-resistive components is explored.All three of them fall into the category of ferromagnetic half-metals.In particular,the Monte Carlo simulations indicate that the TC of Mn2S3 reachs 381 K,noticeably greater than room temperature.These findings present notable advantages for the application of Mn2S3 in spintronic devices.Hence,a prominent spin filtering effect is apparent when employing non-equilibrium Green’s function simulations to examine the transport parameters.The resulting current magnitude is approximately 2×10^(4) nA,while the peak gigantic magnetoresistance exhibits a substantial value of 8.36×10^(16)%.It is noteworthy that the device demonstrates a substantial spin Seebeck effect when the temperature differential between the electrodes is modified.In brief,Mn_(2)X_(3) exhibits outstanding features as a highTC half-metal,exhibiting exceptional capabilities in electrical and thermal drives spin transport.Therefore,it holds great potential for usage in spintronics applications.

Electronic structures of Heusler alloy Co_2FeAl_(1-x)Si_x surface

We have calculated the electronic structures of Co2FeAl1-xSix(101) surface using firstprinciples method based on the density functional theory. Because of the surface effect, the minority spin band gap at the Fermi level disappears at the surface of bulk Co2FeAl1-xSix. However, beneath the surface, the minority spin gap opens at the Fermi level, which indicates that the electronic structures of Co2FeAl1-xSix(101) become close to that of bulk phase. Accordingly, the Co2FeAl1-xSix(101) surface is a composite tri-layer structure that corresponds to the weakening of half-metallic property in Co2FeAl1-xSix films. Even though, the spin polarization of Co2FeAl1-xSix(101) surface is still larger than that of Co2FeAl or Co2FeSi materials, making Co2FeAl1-xSix a promising spintronics material.

Effects of the 3d transition metal doping on the structural, electronic, and magnetic properties of BeO nanotubes

First-principles calculations have been performed on the structural, electronic, and magnetic properties of seven 3d transition-metal （TM） impurities （V, Cr, Mn, Fe, Co, Ni, and Cu） doped armchair （5,5） and zigzag （8,0） beryllium oxide nanotubes （BeONTs）. The results show that there exists a structural distortion around the 3d TM impurities with respect to the pristine BeONTs. The magnetic moment increases for V- and Cr-doped BeONTs and reaches a maximum for Mn-doped BeONT, and then decreases for Fe-, Co-, Ni-, and Cu-doped BeONTs successively, consistent with the predicted trend of Hund＇s rule to maximize the magnetic moments of the doped TM ions. However, the values of the magnetic moments are smaller than the predicted values of Hund＇s rule due to the strong hybridization between the 2p orbitals of the near O and Be ions of BeONTs and the 3d orbitals of the TM ions. Furthermore, the V-, Co-, and Ni-doped （5,5） and （8,0） BeONTs with half-metal ferromagnetism and thus 100% spin polarization character are good candidates for spintronic applications.

Magnetic and electrical properties of zincblende CrAs

This paper reports that 9nm zincblende CrAs is grown by molecular-beam epitaxy on InAs buffer layer. The zb-CrAs shows ferromagnetism at room temperature and the total magnetic moment 3.09 ±0.15μB per CrAs unit. The temperature dependence of zb-CrAs resistance R shows metallic behaviour.

Gd impurity effect on the magnetic and electronic properties of hexagonal Sr ferrites: A case study by DFT

The electronic and magnetic properties of strontium hexa-ferrite(SrFe12O19)are studied in pure state(SrFe12O19)and with dopant in the positions 2 and 3 of Fe atoms(SrGdFe11O19-I and SrGdFe11O19-Ⅱ,respectively)by utilizing a variety of the density functional theory(DFT)approaches including the Perdew-Burke-Ernzerhof generalized gradient approximation(PBE-GGA)and GGA plus Hubbard U parameter(GGA+U).The pure SrFe12O19 is a hard magnetic half-metal with an integer magnetic moment of 64.00μB,while using the GGA+U functional,the magnetic intensity increases,resulting in a magnetic semiconductor with a high integer magnetic moment of 120μB.By doping the Gd atom in the two different positions of Fe,the magnetic moment is increased to 71.68μB and 68.00μB,respectively.The magnetic moment increases and remains an integer;hence,SrGdFe11O19-Ⅱcan be very useful for application in magnetic memories.Moreover,applying the Hubbard parameter turns SrGdFe11O19-I and SrGdFe11O19-Ⅱto magnetic semiconductors with a magnetic moment of 124μB,and the energy gap of both doped structures at spin down is found to be less than the pure case.By studying the electronic density diagram of the atoms of the crystal,it is found that the major effect to create magnetization in the pure case is due to the Fe atom.However,in the doped case,the elements Gd and Fe have the highest moment in the crystal respectively.

Electronic Structures and Magnetic Properties of Co-Adsorbed Monolayer WS2

Using the first-principles density functional theory (DFT) calculations, we study the effects of Co adatom on the electronic and magnetic properties of monolayer WS2. The calculations show that, for the high symmetry adsorption sites (Tw, H and Ts) on the surface of monolayer WS2, Co atom prefers Tw site. The p-d hybridization mechanism for the magnetism results in the splitting of the energy levels near the Fermi energy. A total magnetic moment of ~1.0 μB is found in WS2 system with one Co adsorbed and local magnetic moment which mainly focuses on the adsorption site. For Tw adsorption position, we further investigate the formation energy of the ferromagnetic (FM) and the antiferromagnetic (AFM) states under different monolayer coverage (ML) of Co atoms. The FM configurations are relatively stable at 0.50 ML and 1.0 ML. The local density of states (LDOS) and band calculations reveal that both of them present half-metal ferromagnetic materials’ property, which are the important preparation materials for spintronic devices.

First-principles Study on the Magnetic,Half-metal and Thermoelectric Transport Properties of Inorganic-Organic Hybrid Compounds [C_4N_2H_(12)][Fe_4~Ⅱ(HPO_3)_2(C_2O_4)_3]

The electronic structure, magnetic and half-metal properties of inorganic-organic hybrid compound [C4N2H12][FeoI （HP03）2 （（72 04）3] are investigated by using the full-potential linearized augmented plane wave （FPLAPW） method within density-functional theory （DFT） calculations. The density of states （DOS）, the total energy of the cell and the spontaneous magnetic moment of [C4N2H12][FeII （HP03）2 （C2 04）3] are calculated. The calculation results reveal that the low-temperature phase of [C4N2H12][FeII （HP03）2（C204）3] exhibits a stable ferromagnetic （FM） ground state, and we find that this organic compound is a half-metal in FM state. In addition, we have calculated antiferromagnetically coupled interactions, revealing the existence of antiferromagnetic （AFM）, which is in agreement with the experiment. We have also found that [C4N2HI2][Fe4II （HP03）2（C204）3] is a semiconductor in the AFM state with a band gap of about 0.40 eV. Subsequently, the transport properties for potential thermoelectric applications have been studied in detail based on the Boltzmann transport theory.

Investigation of Possible Half-Metallic Antiferromagnets on Double Perovskites A_(2)BB′O_(6)(A=Ca,Sr Ba;B,B′=Transition Metal Elements)

A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the exception of La.Sr can also be replaced by Ca or Ba whenever HM-AFM was found and similar calculations were then performed in order to probe further possibilities.It was found that A_(2)MoOsO_(6),A_(2)TcReO_(6),A_(2)CrRuO_(6),where A=Ca,Sr,Ba,are all potential candidates for HM-AFM.The AFM of A2BB′O6 comes from both the superexchange mechanism and the generalized double exchange mechanism via the B(t2g)-O2pp-B′(t2g)coupling,With the latter also being the origin of their HM.Also considered were the effects of spin-orbit coupling(SOC)and correlation(+U)by introducing+SOC and+U corrections.It is found that the SOC effect has much less influence than the correlation effect on the HMproperty of the compounds.For A_(2)TcReO_(6)and A_(2)CrRuO_(6),after+U,they become nearlyMott-Insulators.In the future,it is hoped that therewill be further experimental confirmation for these possible HM-AFMcandidates.

High efficiency giant magnetoresistive device based on two-dimensional MXene(Mn_(2)NO_(2))

Due to the unique electronic structure of half-metals,characterized by the conductivity of majority-spin and the band gap of minority-spin,these materials have emerged as suitable alternatives for the design of efficient giant magnetoresistive(GMR)devices.Based on the first-principles calculations,an excellent GMR device has been designed by using two-dimensional(2D)half-metal Mn_(2)NO_(2).The results show that Mn_(2)NO_(2)has sandwiched between the Au/nMn_(2)NO_(2)(n=1,2,3)/Au heterojunction and maintains its half-metallic properties.Due to the half-metallic characteristics of Mn_(2)NO_(2),the total current of the monolayer device can reach up to 1500 nA in the ferromagnetic state.At low voltage,the maximum GMR is observed to be 1.15×1031%.Further,by increasing the number of layers,the ultra-high GMR at low voltage is still maintained.The developed device is a spintronic device exhibiting the highest magnetoresistive ratio reported theoretically so far.Simultaneously,a significant negative differential resistance(NDR)effect is also observed in the heterojunction.Owing to its excellent half-metallic properties and 2D structure,Mn_(2)NO_(2)is an ideal energy-saving GMR material.

Electronic and magnetic properties of V-and Cr-doped zinc-blende AlN

The electronic and magnetic properties of the zinc-blende aluminum nitride doped with V and Cr are studied using the density functional theory(DFT),namely the KKR-CPA-PBE method.Pure Al N is found to be a wide band gap semiconductor,and doping V and Cr single impurities generate ferromagnetic half-metallic behavior.Moreover,the values of the formation energy reveal that these compounds are stable systems for all dopant concentrations.A self-consistent energy minimization scheme determines the ferromagnetic state as the stable magnetic state for V-and Cr-doping Al N.A double exchange mechanism is identified as the mechanism responsible for magnetism in our systems.When increasing doping impurities,the total magnetic moments increase linearly and the Curie temperature TC,calculated using the mean-field approximation,shows a significant change.The present findings reveal Cr-and V-doped zincblende Al N as potential candidates for high Curie temperature ferromagnetic materials.

Diverse magnetism in stable and metastable structures of CrTe

In this paper,we systematically investigated the structural and magnetic properties of CrTe by combining particle swarm optimization algorithm and first-principles calculations.By considering the electronic correlation effect,we predicted the ground-state structure of CrTe to be NiAs-type(space group P63/mmc)structure at ambient pressure,consistent with the experimental observation.Moreover,we found two extra meta-stable Cmca and R3m structures which have negative formation enthalpy and stable phonon dispersion at ambient pressure.The Cmca structure is a layered antiferromagnetic metal.The cleaved energy of a single layer is 0.464 J/m^(2),indicating the possible synthesis of CrTe monolayer.The R3m structure is a ferromagnetic half-metal.When external pressure is applied,the ground-state structure of CrTe transitions from P63/mmc structure to R3m structure at a pressure of 34 GPa,then to Fm3m structure at 42 GPa.We thought these results help to motivate experimental studies of the CrTe compounds in the application of spintronics.

Elastic and optical properties of zinc-blende CrSb and its effective mass

The elastic, optical, and effective mass properties of CrSb in zinc-blende（ZB） phase were investigated.The calculations were carried out using the full-potential linearized augmented plane wave plus local orbital according to the density functional theory. The results of elastic calculations by generalized gradient approximation and local density approximation approximations indicate that ZB CrSb is a ductile material and its Debye temperature is rather low. Band structure and density of state calculations introduce the ZB CrSb as a half-metal with spin polarization of100 %. In metal state, 16 th and 17 th bands cut off the Fermi level. Calculations study the effective mass, Fermi velocity,and Fermi surface at 16 th and 17 th bands. In continue,optical quantities such as dielectric function, energy loss function, and optical conductivity were investigated.

Preparation and Magnetic Properties of Submicron CrO2 Thin Film on Poly-crystal TiO2 Film

The submicron chromium dioxide（CrO2） thin film was fabricated on a poly-crystal titania（TiO2） film using Si wafers as substrates by atmospheric pressure chemical vapor deposition（CVD） method. X-Ray diffraction patterns show that the CrO2 films were pure rutile structure. Scanning electron microscopy（SEM） images indicate that the CrO2 films consisted of submicron grains with a grain size of 250--750 rim. The magnetic researches reveal that the magnetic easy axis is parallel to the films, and at room temperature, the CrO2 films show linear magnetoresistance.