Magnetic field effects on the magnetism of Zr3FeH5.3

Zr₃FeH_5.3 exhibits hydrogen-induced magnetism below an ordering temperatureT ₀=135 K. Comparison of three fit models for analysis of the zero field Mössbauer spectra belowT ₀ is presented. The models are based on discrete and distributed static hyperfine fields and magnetic relaxation. The response of Zr₃FeH_5.3 to an applied field of 6.9 T indicates that antiferromagnetic interactions are present with spin canting also possible.     

Hydrogen desorption in Zr3Fe H5.5

Hydrogen desorption during heat treatments of (crystalline) Zr₃FeH_5.5 was studied by Mössbauer spectroscopy (MS), X-ray (powder) diffraction (XRD) and thermal gravimetry (TG). In case of sufficiently slow heating rate all hydrogen effuses below 650°K and no phase segregation occurs. At higher temperatures retained hydrogen induce phase separation into Fe₂Zr (or more likely Fe₂ZrH_x) and zirconium hydride. The existence of a highly disordered f.c. tetragonal ternary hydride phase was also detected both by XRD (a_o=4.76 Å, c=4.96 Å) and MS .     

Similarity of optical properties of hydrides and semiconductors for antireflection coatings

The electronic structure and optical properties of the complex hydrides Ca₂FeH₆, Ca₂RuH₆, Mg₂FeH₆, Mg₂RuH₆, Sr₂FeH₆, Sr₂RuH₆ and Sr₂OsH₆ were studied using first-principles calculations. Optical spectra of the hydrides were compared with those of SiN _x , In₂O₃ and ZnO determined from theoretical calculations and measured experimentally. Based on an analysis of band structure, it is found that the electrical conductivity of the hydrides is expected to be poor. However, optical properties of the hydrides in the energy range 0–3 eV are found to be almost the same as those of SiN _x , In₂O₃, ZnO and TiO₂. Hydrides are suggested to be used as antireflection layers and for passivation of surface and bulk defects. This finding could be useful for electronic device technology including solar cells.     

Structural and vibrational properties of Ca2FeH6 and Sr2RuH6

The structural and vibrational properties of the isostructural compounds Ca₂FeH₆ and Sr₂RuH₆ are determined by periodic DFT calculations and compared with their previously published experimental crystal structures as well as new experimental vibrational data. The analysis of the vibrational data is extended to the whole series of alkaline-earth iron and ruthenium hydrides A₂TH₆ (A=Mg, Ca, Sr; T=Fe, Ru) in order to identify correlations between selected frequencies and the T-H bond length. The bulk moduli of Ca₂FeH₆ and Sr₂RuH₆ have also been determined within DFT. Their calculated values prove to compare well with the experimental values reported for Mg₂FeH₆ and several other compounds of this structure.     

Structural, vibrational and thermodynamic properties of Mg2 FeH6 complex hydride

Mg₂FeH₆, which has one of the highest hydrogen storage capacities among Mg based 3d-transitional metal hydrides, is considered as an attractive material for hydrogen storage. Within density-functional perturbation theory (DFPT), we have investigated the structural, vibrational and thermodynamic properties of Mg₂FeH₆. The band structure calculation shows that this compound is a semiconductor with a direct X-X energy gap of 1.96 eV. The calculated phonon frequencies for the Raman-active and the infrared-active modes are assigned. The phonon dispersion curves together with the corresponding phonon density of states and longitudinal-transverse optical (LO-TO) splitting are also calculated. Findings are also presented for the temperature-dependent behaviors of some thermodynamic properties such as free energy, internal energy, entropy and heat capacity within the quasi-harmonic approximation based on the calculated phonon density of states.     

Moment formation upon hydrogen absorption in Hf2Fe

The cubic intermetallic compound Hf₂Fe can absorb large quantities of hydrogen gas without changing its crystal structure (Ti₂Ni type). Whereas the Fe atoms do not have a moment in Hf₂Fe we measured a moment of about 0.9 u_B per Fe atom in the hydride Hf₂FeH₃. The ferromagnetic Curie temperature of Hf₂FeH₃ is T_c = 73 K. Using ⁵⁷Fe Mössbauer effect spectroscopy we found that the isomer shift changes +0.40 mms^?1 upon H₂ take-up. This isomer shift change is not compatible with an explanation of the observed moment increase in terms of charge transfer from Fe to H.     

非晶态Cu56Zr44合金的结构及其等温退火晶化过程的研究

利用X射线衍射技术、差示扫描量热分析技术和透射电子显微镜研究了非晶态Cu₅₆Zr₄₄合金的结构及其等温退火条件下的晶化过程.实验结果表明,非晶态Cu₅₆Zr₄₄合金在室温下的短程结构类似于硬球无规密堆积分布.在703K过冷液相区内等温退火时发现,当退火时间为3min时,晶化产物主要为Cu₈Zr₃相;当退火时间为6min时,Cu₈Zr₃关键词： 非晶态 56Zr₄₄合金')" href="#">Cu₅₆Zr₄₄合金 结构 等温退火     

Structural and electrical transport properties of FeH x under high pressures and low temperatures

We present the first successful in situ simultaneous measurement of the electrical resistance and X-ray diffraction of FeH _x (x～ 1) under high-pressure H₂ up to 25.5 GPa and low temperatures down to 9 K. The electrical resistivity ρ showed a sharp increase with the formation of iron-hydride FeH _x (x～ 1) at 3.5 GPa. The ?′-phase of FeH _x was found to be metallic up to 25.5 GPa. The ρ vs. T curves up to 16.5 GPa approximately follow Fermi-liquid law below 25 K. However, T ⁵ was found to be better fitting at 25.5 GPa. This change can be considered to be related to the previously reported ferromagnetism collapse at corresponding pressure.     

First-principles FP-LAPW calculations and X-ray spectroscopy studies of the electronic structure of Zr3V3O and Zr3V3O0.6 oxides

Electronic properties of Zr₃V₃O oxide, a very promising hydrogen-storage material, were studied both from theoretical and experimental points of view employing the full potential linearized augmented plane wave (FP-LAPW) method as well as X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES). Total and partial densities of states of the constituting atoms of Zr₃V₃O have been derived from the FP-LAPW calculations. These data indicate that, the O 2p-like states are the dominant contributors in the bottom of the valence band, whilst the top of the valence band and the bottom of the conduction band of Zr₃V₃O are dominated by contributions of the V2 3d-like states, with slightly smaller contributions of the V1 3d-like states as well. Significant contributions of the Zr 4d-like states throughout the whole valence-band region and near the bottom of the conduction band are also characteristic of the electronic structure of Zr₃V₃O. The XPS valence-band spectra and the XES Zr Lβ_2,15, V L_α and O K_α bands have been derived and compared on a common energy scale for Zr₃V₃O and Zr₃V₃O_0.6 oxides. This comparison of the experimental spectra was found to be in excellent agreement with the results of the FP-LAPW calculations. In addition, the XPS Zr 3d, V 2p and O 1s core-level binding energies have been measured for Zr₃V₃O and Zr₃V₃O_0.6 oxides.     

Electronic structure and stability of complex hydrides Mg<Subscript>2</Subscript><Emphasis Type="Italic">M</Emphasis>H<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> (<Emphasis Type="Italic">M</Emphasis> = Fe,Co)

This paper reports on the results of theoretical investigations carried out for the hydrides Mg₂FeH₆ and Mg₂CoH₅ and the mixed hydride Mg₂(FeH₆)_0.5(CoH₅)_0.5 in terms of the full-potential linearized augmented plane wave (FLAPW) method. It has been shown that the partial substitution of the Co atoms for the Fe atoms leads to a slight increase in the stability of the hydride, but, at the same time, makes it impossible to increase the stability of the alloy. The high stability of the hydrides under investigation has been explained by the strong bonding between atoms of the transition metal and hydrogen.     

Experimental and Theoretical Study of Hydrogen Atom Abstraction from C2H6 and C4H10 by Zirconium Oxide Clusters Anions

使用配有团簇产生和化学反应源的飞行时间质谱装置,研究了锆氧阴离子团簇Zr_xOy^-与乙烷和丁烷的反应. 在反应中发现了Zr₂O₅H^-和Zr₃O₇H^-产物. 用密度泛函理论研究了乙烷在Zr₂O₅^-上的反应通道,发现乙烷脱氢反应可以发生,从而证明观察到的产物是源于脱氢反应. 该工作揭示了锆氧负离子团簇与烷烃反应中的新通道.     

Local structure of amorphous Zr3Fe

It is shown that the chemical short-range order (CSRO) of amorphous Zr₃Fe studied by Mössbauer spectroscopy is similar to the CSRO of metastable crystalline Zr₃Fe formed during crystallization while it is quite different from the CSRO of the stable crystalline compounds (ZrFe₂, Zr₂Fe and orthorhombic Zr₃Fe).     

Interfacial properties of black phosphorus/transition metal carbide van der Waals heterostructures

Owing to its outstanding electronic properties, black phosphorus (BP) is considered as a promising material for next-generation optoelectronic devices. In this work, devices based on BP/MXene (Zr_n+1C _n T₂, T = O, F, OH, n = 1, 2) van der Waals (vdW) heterostructures are designed via first-principles calculations. Zr_n+1C _n T₂ compositions with appropriate work functions lead to the formation of Ohmic contact with BP in the vertical direction. Low Schottky barriers are found along the lateral direction in BP/Zr₂CF₂, BP/Zr₂CO₂H₂, BP/Zr₃C₂F₂, and BP/Zr₃C₂O₂H₂ bilayers, and BP/Zr₃C₂O₂ even exhibits Ohmic contact behavior. BP/Zr₂CO₂ is a semiconducting heterostructure with type-II band alignment, which facilitates the separation of electron-hole pairs. The band structure of BP/Zr₂CO₂ can be effectively tuned via a perpendicular electric field, and BP is predicted to undergo a transition from donor to acceptor at a 0.4 V/Å electric field. The versatile electronic properties of the BP/MXene heterostructures examined in this work highlight their promising potential for applications in electronics.     

Insight into structural,mechanical, electronic and thermodynamic properties of intermetallic phases in Zr–Sn system from first-principles calculations

The structural, phase stabilities, mechanical, electronic and thermodynamic properties of intermetallic phases in Zr–Sn system are investigated by using first-principles method. The equilibrium lattice constants, enthalpy of formation (ΔH^form) and elastic constants are obtained and compared with available experimental and theoretical data. The configuration of Zr₄Sn is measured with reasonable precision. The ΔH^form of five hypothetical structures are obtained in order to find possible metastable phase for Zr–Sn system. The mechanical properties, including bulk modulus, shear modulus, Young's modulus and Poisson's ratio, are calculated by Voigt–Reuss–Hill approximation and the Zr₅Sn₄ and Zr₅Sn₃ show excellent mechanical properties. The electronic density of states for Zr₅Sn₄, Zr₅Sn₃ and cP8-Zr₃Sn are calculated to further investigate the stability of intermetallic compounds. Through the quasi-harmonic Debye model, the Debye temperature, heat capacity and thermal expansion coefficient under temperature of 0–300 K and pressure of 0–50 GPa for Zr₅Sn₃ and Zr₅Sn₄ are deeply investigated.     

密度泛函理论对ZrnPd团簇结构和性质的研究

用B3LYP/LANL2DZ方法对Zr_nPd(n =1—13)团簇的平衡几何结构、能量、频率、电子性质和磁性进行了计算.研究表明,Pd原子位于表面的异构体更为稳定,其中Zr₇Pd,Zr₁₂Pd团簇稳定性高,是幻数团簇,此外,相对于Zr_nCo与Zr_nFe团簇,Zr_nPd团簇参与化学反应的能力较弱,化学稳定性更     

Isomer shifts in Zr2Fe and Zr3Fe

The⁵⁷Fe isomer shifts in the crystalline compounds Zr₂Fe and Zr₃Fe are calculated. We use the standard first-principles linear-muffin-tin-orbital formalism in the atomic sphere approximation (LMTO-ASA) to obtain the electronic structure of the compounds. The electronic structure of pure Fe was also calculated with the same formalism, where the local spin density approximation for the exchange correlation term is used. We found that the calculated isomer shift values are in good agreement with the experimental values for Zr₂Fe and Zr₃Fe found in the literature.     

X-ray Kβ-and L2,3-emission bands of pure silicon and silicon in ZrSi compounds

The intensity distribution of the K_β-and L_2,3-emission bands of pure silicon and silicon in ZrSi₂, Zr₃Si₂, Zr₅Si₃ and Zr₃Si are investigated. Some of the aspects of the electronic structure of these compounds are discussed.     

Sintering and characterization of alkaline-earth-doped and zirconium-defficient Na3Zr2Si2PO12

The sintering behavior of Na₃Zr₂Si₂PO₁₂, Na_3.08Zr_1.96X_0.04Si₂PO₁₂ (X = Mg, Ca, Sr, Ba), Na₃Zr_1.5 Si₂PO₁₂, and Na₃Zr_1.3Si₂PO₁₂ was studied between 900 and 1300°C. Microstructural examination indicated that liquid-phase sintering had occurred and that free ZrO₂ was present in all of the samples. X-ray diffraction indicated that the NASICON and ZrO₂ were monoclinic and that doping the Na₃Zr₂Si₂PO₁₂ with 0.02 mole% alkaline-earth ions (compared to the ZrO₂ content) did not significantly increase the unit-cell volume.     

密度泛函理论研究ZrnCo(n=1—13)团簇的结构和磁性

利用密度泛函理论中的广义梯度近似对Zr_nCo(n=1—13)团簇进行了结构优化、能量和频率的计算,研究了Zr_nCo团簇的平衡几何结构、稳定性、电子性质和磁性.结果表明：Zr₄Co,Zr₇Co,Zr₉Co和Zr₁₂Co团簇的基态稳定性较高,是幻数团簇,尤其是Zr₁₂Co团簇基态为I_{h< 关键词： n}Co团簇')" href="#">Zr_nCo团簇 平衡几何结构 稳定性和磁性     

Blue and red long lasting phosphorescence (LLP) in β-Zn3(PO4)2:Mn,Zr

Multi-color long lasting phosphorescent (LLP) phenomenon in β-Zn₃(PO₄)₂:Mn²⁺,Zr⁴⁺ was systematically investigated. It is found that the red (λ_Em=616 nm) LLP performance of Mn²⁺ such as brightness and duration is largely improved, and that the blue (λ_Em=475 nm) LLP of Zr⁴⁺ with lower intensity appears when Zr⁴⁺ ions are co-doped into the matrix. The fluorescence, phosphorescence and thermoluminescence (TL) spectra show that Mn²⁺ ion is solely expected as a luminescent center, while Zr⁴⁺ ion not only acts as a luminescent center, but also induces an electron trap (Trap_Zr) associated with a TL peak at 344 K. The trap depth for Trap_Zr is 0.25 eV, while that for the intrinsic trap is 0.38 eV, associated with a dominant peak at 385 K for Zn₃(PO₄)₂:Mn²⁺. The Zr⁴⁺-induced trap with suitable depth is responsible for the improvement of the red LLP of Mn²⁺ ion and the appearance of the blue LLP of Zr⁴⁺ ion. The LLP mechanism is also investigated.