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Interplay between geometric and electronic structures of Pt entities over TiO_(2) for CO oxidation

Science China Chemistry 2024年第2期67卷 705-714页

作者： Xixiong Zhang Wen Shi Shaobo Han Yong Li Wenjie Shen School of Chemistry Dalian University of TechnologyDalian116024China State Key Laboratory of Catalysis Dalian Institution of Chemical PhysicsChinese Academy of SciencesDalian116023China

Monodispersed Pt colloids with a mean size of 2 nm were deposited uniformly on the {110} facets of a rod-shaped rutile TiO_(2),forming a well-defined Pt/TiO_(2) *** treatment of this precursor at elevated temperatures re-dispersed the Pt particles into clusters and ***-calcination at 673 K partially oxidized the Pt particle surface,while calcination at 773 K yielded Pt Oxclusters of 1.6 nm in 7–8 atomic *** calcination at 873 K formed a mixture of raft-like PtO_(x) clusters(1.6 nm,1–2 atomic layers) and cationic *** tested for CO oxidation at 373 K,the Pt particles showed a higher activity than the Pt Oxclusters,whereas the cationic single-atoms were much less *** H_(2)-reduction at 473 K converted the partially oxidized Pt particles into the metallic species,but they were encapsulated by TiO_(2)–xoverlayers because of the strong metal–support interactions,which decreased the activity dramatically.H_(2)-reduction of the PtO_(x) clusters at473 K enhanced the fraction of metallic Pt species without changing the size and geometry,and promoted the activity substantially.H_(2)-treatment of Pt single-atoms at 473 K increased the activity only moderately because most Pt species still kept at cationic *** results straightforwardly differentiated the catalytic behavior of Pt particles,clusters and single-atoms at the same metal loading and over the same TiO_(2) support,and further demonstrated that the electronic structures of Pt entities played a decisive role in the catalytic oxidation,in addition to the specified sizes.

关键词： Pt/TiO_(2)catalyst size effect Pt clusters active sites electronic structures CO oxidation

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Probing electronic structures of transition metal complexes using electron paramagnetic resonance spectroscopy

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Magnetic Resonance Letters 2023年第1期3卷 43-60,I0003页

作者： Shengfa Ye State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian116023China

Electron paramagnetic resonance(EPR)or electron spin resonance(ESR)has been widely employed to characterize transition metal ***,because of the high degree of complexity of transition metal EPR spectra,how to extract the underlying electronicstructure information inevitably poses a major challenge to beginners,in particular for systems with S>1/*** fact,the physical principles of transition metal EPR have long been well-established and since 1970s a series of dedicated voluminous monographs have been published *** surprisingly,they are not appropriate stating points for novices to grasp a panorama of the profound theory prior to scrutinizing in-depth *** present review aims to fill this gap to provide a perspective of transition metal EPR and unveil some peculiar subtleties thereof on the basis of our recent work.

关键词： EPR electronic structures Transition metal complexes Spin Hamiltonian

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electronic structures and optical properties of TiO_2:Improved density-functional-theory investigation

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Chinese Physics B 2012年第5期21卷 508-514页

作者：龚赛刘邦贵 Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of Sciences

TiO2 has been recently used to realize high-temperature ferromagnetic *** fact,it has been widely used for a long time as white pigment and sunscreen because of its whiteness,high refractive index,and excellent optical ***,its electronic structures and the related properties have not been satisfactorily ***,we use Tran and Blaha＇s modified Becke-Johnson（TB-mBJ） exchange potential（plus a local density approximation correlation potential） within the density functional theory to investigate electronic structures and optical properties of rutile and anatase *** comparative calculations show that the energy gaps obtained from mBJ method agree better with the experimental results than that obtained from local density approximation（LDA） and generalized gradient approximation（GGA）,in contrast with substantially overestimated values from many-body perturbation（GW） *** for optical dielectric functions（both real and imaginary parts）,refractive index,and extinction coefficients as functions of photon energy,our mBJ calculated results are in excellent agreement with the experimental *** further analysis reveals that these excellent improvements are achieved because mBJ potential describes accurately the energy levels of Ti 3d *** results should be helpful to understand the high temperature ferromagnetism in doped *** approach can be used as a standard to understand electronic structures and the related properties of such materials as TiO2.

关键词： rutile anatase electronic structures optical properties

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electronic structures and thermodynamic stabilities of aluminum-based deuterides from first principles calculations

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Chinese Physics B 2011年第1期20卷 534-540页

作者：叶小球罗德礼桑革敖冰云 Science and Technology on Surface Physics and Chemistry Laboratory

The alanates （complex aluminohydrides） have relatively high gravimetric hydrogen densities and are among the most promising solid-state hydrogen-storage materials. In this work, the electronic structures and the formation enthalpies of seven typical aluminum-based deuterides have been calculated by the plane-wave pseudopotential method, these being A1D3, LiA1D4, Li3A1D6, BaA1D5, Ba2A1D7, LiMg（A1D4）3 and LiMgA1D6. The results show that all these compounds are large band gap insulators at 0 K with estimated band gaps from 2.31 eV in A1D3 to 4.96 eV in LiMg（A1D4）3. The band gaps are reduced when the coordination of A1 varies from 4 to 6. Two peaks present in the valence bands are the common characteristics of aluminum-based deuterides containing A1D4 subunits while three peaks are the common characteristics of those containing A1D6 subunits. The electronic structures of these compounds are determined mainly by aluminum deuteride complexes （A1D4 or A1D6） and their mutual interactions. The predicted formation enthalpies are presented for the studied aluminum-based deuterides.

关键词： hydrogen storage material complex aluminohydrides electronic structures density functional theory

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electronic structures,magnetic properties,and martensitic transformation in all-d-metal Heusler-like alloys Cd2MnTM(TM=Fe,Ni,Cu)

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Chinese Physics B 2020年第8期29卷 407-412页

作者： Yong Li Peng Xu Xiaoming Zhang Guodong Liu Enke Liu Lingwei Li Institute of Advanced Magnetic Materials School of Materials and Environmental EngineeringHangzhou Dianzi UniversityHangzhou 310012China Key Laboratory of Electromagnetic Processing of Materials(Ministry of Education) Northeastern UniversityShenyang 110819China School of Materials Science and Engineering Hebei University of TechnologyTianjin 300130China Institute of Physics Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory Dongguan 523808China

The electronic structures,magnetic properties,and martensitic transformation in all-d-metal Heusler-like alloys Cd2MnTM(TM=Fe,Ni,Cu)were investigated by the first-principles calculations based on density-functional *** results indicate that all three alloys are stabilized in the ferromagnetic L21-type *** total magnetic moments mainly come from Mn and Fe atoms for Cd2MnFe,whereas,only from Mn atoms for Cd2MnNi and *** magnetic moment at equilibrium lattice constant of Cd2MnFe(6.36μB)is obviously larger than that of Cd2MnNi(3.95μB)and Cd2MnCu(3.82μB).The large negative energy differences(ΔE)between martensite and austenite in Cd2MnFe and Cd2MnNi under tetragonal distortion and different uniform strains indicate the possible occurrence of ferromagnetic martensitic transformation(FMMT).The minimum total energies in martensitic phase are located with the c/a ratios of 1.41 and 1.33 for Cd2MnFe and Cd2MnNi,*** total moments in martensitic state still maintain large values compared with those in cubic *** study is useful to find the new all-d-metal Heusler alloys with FMMT.

关键词： all-d-metal Heusler-like alloys electronic structures magnetic properties martensitic transformation

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electronic structures and thermoelectric properties of solid solutions CuGa_(1-x) In_xTe_2 : A first-principles study

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Chinese Physics B 2014年第3期23卷 463-468页

作者：薛丽徐斌易林 Department of Physics Huazhong University of Science and Technology Department of Mathematics and Information Sciences North China Institute of Water Conservancy and Hydroelectric Power

The electronic structures of solid solutions CuGal_xlnxTe2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearly increase with the increase of the In composition, which are in good agreement with the available experimental results. The calculated band structures with the modified Becke-Johnson potential show that all solid solutions are direct gap conductors. The band gap decreases linearly with In composition increasing. Based on the electronic structure calculated, we investigate the thermoelectric properties by the semi-classical Boltzmann transport theory. The results suggest that when Ga is replaced by In, the bipolar effect of Seebeck coefficient S becomes very obvious. The Seebeck coefficient even changes its sign from positive to negative for p-type doping at low carrier concentrations. The optimal p-type doping concentrations have been estimated based on the predicted maximum values of the power factor divided by the scattering time.

关键词： CuGa1-xlnxTe2 electronic structures thermoelectric properties first-principles

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electronic structures of an(8,0)boron nitride/carbon nanotube heterojunction

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Journal of Semiconductors 2010年第1期31卷 14-16页

作者：刘红霞张鹤鸣宋久旭张志勇 Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University Key Laboratory of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices School of MieroelectronicsXidian University School of electronic Engineering Xi'an Shiyou University Information Science and Technology Institution Northwest University

The electronic structure of the heterojunction is the foundation of the study on its working mechanism. Models of the heterojunctions formed by an （8, 0） boron nitride nanotube and an （8, 0） carbon nanotube with C-B or C-N interface have been established. The structures of the above heterojunctions were optimized with first-principle calculations based on density functional theory. The rearrangements of the heterojunctions concentrate mainly on their interfaces. The highest occupied molecular orbital and the lowest unoccupied molecular orbital of the heterojunctions distribute in the carbon nanotube section. As the band offsets of the above heterojunctions are achieved with the average bond energy method, the band structure is plotted.

关键词： boron nitride/carbon nanotube heterojunction density functional theory the average bond energymethod electronic structures

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electronic structures and magnetocrystalline anisotropy energies of ordered Co_(1-x)Ni_x alloys:a first principles study

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Chinese Physics B 2010年第12期19卷 419-424页

作者：张莎庞华方阳李发伸 Institute of Applied Magnetics Lanzhou University

The electronic structures and magnetocrystalline anisotropy （MA） of ordered hexagonal close-packed （hcp） Co1-xNix alloys are studied using the full-potential linear-augmented-plane-wave （FLAPW） method with general- ized gradient approximation （CGA）. Great changes of magnetocrystalline anisotropy energy （MAE） are gained with different Ni compositions. Also, in-plane magnetocrystalline anisotropy is obtained for Co15Ni in which the Snoek＇s limit is exceeded. It is found that the changes of the symmetry of the crystal field on Ni induce small variations in band structures around the Fermi level under different compositions, which plays an important role in modulating the magnetization direction, where the hybridization between Co-3d and Ni-3d orbits is of special importance in deciding the magnetocrystalline anisotropy of itinerant states. The rigid-band model is inapplicable to explain the evolution of magnetocrystalline anisotropy energy with Ni composition, and it is also inadequate to predict the magnetocrystalline anisotropy energy through the anisotropy of the orbital magnetic moment.

关键词： first principles anisotropy electronic structures

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electronic structures and optic properties of Fe2TiO5 using LSDA+U approach

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Progress in Natural Science:Materials International 2013年第4期23卷 413-419页

作者： Lei Jin Chungen Zhou School of Materials Science and Engineering Beijing University of Aeronautics and Astronautics Key Laboratory of Aerospace Materials and Performance (Ministry of Education)

The magnetic properties,band structure,density of states(DOS) and optical properties of ferromagnetic Fe2TiO5were calculated by a plane wave pseudopotential method based on the local spin density approximation(LSDA) and the LSDA plus Hubbard U(LSDA+U) theory and compared with the known experimental and theoretical *** choosing the opportune Hubbard U parameter 4 eV,LSDA+U gives magnetic moments of 3.80 mB/Fe(3d orbital),which contribute the main magnetic moments to *** inclusion of U changes the band gap of Fe2TiO5and gives a value in better agreement with previous *** fnd that strong correlations dramatically change the density of states and band structures.A detailed analysis shows that the LSDA+U method provides the better description of electronic structures like this *** optical properties were explored *** is no ab-initio study related to Fe2TiO5at *** fndings provide good theoretical understanding for Fe2TiO5.

关键词： Fe2TiO5 Magnetic properties electronic structures Optical properties LSDA+U

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electronic structures and optical properties of a SiC nanotube with vacancy defects

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Journal of Semiconductors 2013年第2期34卷 1-5页

作者：宋久旭杨银堂王平郭立新张志勇 Key Laboratory of Ministry of Education for Wide Band Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University School of electronic Engineering Xian Shiyou University School of Science Xidian University Information Science and Technology Institution Northwest University

Based on first-principle calculations, the electronic structures and optical properties of a single-walled （7, 0） SiC nanotube （SiCNT） with a carbon vacancy defect or a silicon vacancy defect are investigated. In the three silicon atoms around the carbon vacancy, two atoms form a stable bond and the other is a dangling bond. A similar structure is found in the nanotube with a silicon vacancy. A carbon vacancy results in a defect level near the top of the valence band, while a silicon vacancy leads to the formation of three defect levels in the band gap of the nanotube. Transitions between defect levels and energy levels near the bottom of the conduction band have a close relationship with the formation of the novel dielectric peaks in the lower energy range of the dielectric function.

关键词： SiC nanotube vacancy defect first-principles study electronic structures optical properties

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