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1.
The mechanism of laser ablation of 2Cu(CO3)·Cu(OH)2 at 308 nm is investigated by time-of-flight mass spectroscopy at laser fluences in the range of 0.07 to 0.6 Jcm-2. The neutral and ion composition of the plume reveals the presence of Cu, Cu2O, CuO, H2O and CO2, which appear as free species or forming clusters. Plume composition is compatible with a thermal ablation mechanism which involves chemical processes similar to those reported for the purely thermal decomposition of the target. Velocity distributions of neutral species in the plume are measured and fitted to shifted Maxwell–Boltzmann time distributions; the best fitting yields flow velocities of 0.07 cms-1 for CO2 and Cu and 0.04 cms-1 for Cu2, which is compatible with an expansion regime characterized by weak interaction of the ejected particles. PACS 82.30.Nr; 78.70.-g  相似文献   

2.
S. Tanaka  R. Yang  M. Kohyama 《哲学杂志》2013,93(32):5123-5135
Adhesive and mechanical properties of the O-terminated (O-rich) α-Al2O3(0001)/Cu(111) interface have been examined by the first-principles pseudopotential method. Strong Cu–O covalent and ionic interactions exist, such as Cu3d–O2p hybridization and substantial electron transfer from Cu to O, which result in larger adhesive energy, greater tensile strength and larger interfacial Young's moduli than the Al-terminated (stoichiometric) interface with electrostatic–image and Cu–Al hybridization interactions. Substantial effects of interfacial Cu–O coordination are also present. Changes in the interface electronic structure for cleavage have been examined. Cu–O interlayer potential curves have been analyzed using the universal binding energy relation and compared with Cu–Al and Cu–Cu curves, which is valuable for the development of effective interatomic potentials in large-scale simulations.  相似文献   

3.
<正>Using first-principles total energy method,we study the structural,the electronic and the magnetic properties of the MnNi(110) c(2×2) surface alloy.Paramagnetic,ferromagnetic,and antiferromagnetic surfaces in the top layer and the second layer are considered.It turns out that the substitutional alloy in the outermost layer with ferromagnetic surface is the most stable in all cases.The buckling of the Mn-Ni(110) c(2×2) surface alloy in the top layer is as large as 0.26 A(1 A=0.1 nm) and the weak rippling is 0.038 A in the third layer,in excellent agreement with experimental results.It is proved that the magnetism of Mn can stabilize this surface alloy.Electronic structures show a large magnetic splitting for the Mn atom,which is slightly higher than that of Mn-Ni(100) c(2×2) surface alloy(3.41 eV) due to the higher magnetic moment.A large magnetic moment for the Mn atom is predicted to be 3.81μB.We suggest the ferromagnetic order of the Mn moments and the ferromagnetic coupling to the Ni substrate,which confirms the experimental results.The magnetism of Mn is identified as the driving force of the large buckling and the work-function change.The comparison with the other magnetic surface alloys is also presented and some trends are predicted.  相似文献   

4.
A complete solid solution range exists between the systems YBa2Cu3O7−δ and (Pb,Cu)Sr2(Ca,Y)Cu2O7−δ has been found with general stoichiometry (Pb0.75xCu1−0.75x)(Sr2xBa2−2x)(Ca0.5xY1−0.5x)Cu2O7−δ. Energy dispersive spectrometry and X-ray diffraction identified that a true solid solution exists. Superlattice structures observed by electron diffraction across the solid solution range have a modulation range have a modulation periods along a* which can be varied by altering both the compositional parameter x and the overall oxygen content. The existence of these superlattices infers that the solid solution is non-random and therefore thermodynamically non-ideal. The superconducting transition temperatures, Tc, across the solid solution range are also strongly dependent on the composition, x, but no direct relationship with the modulation period has been established. From these studies it may be concluded that the solid solution between known superconductors is possible, although involving some partial ordering of the lattice, but ordering of cations in the rock-salt to charge reservoir layer is not a significant factor in determining the superconducting properities, which depend more closely on the overall composition and hence on the ability of the charge reservoir layer to transfer charge to the superconducting layers.  相似文献   

5.
The two-dimensional electronic energy bands induced by adsorption of atomic oxygen on Cu(110) are measured with angle-resolved photoelectron spectroscopy (ARUPS). Three oxygen-derived bonding bands and two Cu - derived antibonding bands are found below the Fermi energy. The dispersions can be described by assuming nearest-neighbour σ and π CuO bonds along the [001] direction with oxygen in a long bridge site.  相似文献   

6.
Phonon anomaly was observed below 140 K for the absorption area (lnA) and the isomer shift () plotted against the temperature (T) in the119Sn Mössbauer study of the Bi2Sr2Ca(Cu0.995Sn0.005)2O8–y superconductor (glass-ceramic,T c(on)=86 K), which was prepared by heat treatment of the glassy sample. The anomaly suggests that the softening (quenching) of the lattice vibration causes the superconducting transition, as was observed in several YBa2(Cu, Sn)3O7–y superconductors. Fitting of the theoretical curve for the normal phonon of the combined Debye and Einstein model to the lnA versusT and versusT plots yielded D and E of 240 and 140 K, respectively. These results suggest that the probe (Sn4+) was located at the interstitial site close to the Cu site, and the softening of the Cu site vibration could be detected before the superconducting transition took place. Disordered structure seems to be favorable for the detection of phonon anomaly in the Bi system.  相似文献   

7.
Bond properties of the chalcopyrite and (defect) stannite phases in the Cu–(In,Ga)–Se system are compared in view of the bond overlap population calculated by the molecular orbital calculation of the DV-Xα method. Bond stretching force constant α is estimated for the stannite phases through the bond Ovlp. The Cu–Se and In(Ga)–Se bonds in defect stannite structure are considered to be mechanically weakened by the 2b-site vacancies. We estimate the weakened force constants to be 60–70% of those in the chalcopyrite structure. On the other hand, in In(Ga)-rich stannite, In(Ga)4d–Se8i and In(Ga)2b–Se8i bonds are estimated to be tighter by 23–25 and 8–9%, respectively, than In(Ga)4b–Se8d bond in the chalcopyrite structure. The Γ1 frequencies of the stannite phases are also calculated using the estimated force constants. Characteristic Raman signals peaked at 160–175 cm−1 observed for the Cu(In1−xGax)3Se5 system are explained by the Cu-rich phase for the Cu–In–Se system, and the phase combination of Cu-rich and Ga2aV2b types for the Cu–Ga–Se system from these calculations.  相似文献   

8.
We present new parametrisations of the parton distribution functions of the photon including the first parametrisation in next-to-leading order QCD. We take into account some recent theoretical considerations pertaining to the gluon content of the photon,g γ. We argue that if an evolution is started at very lowQ 2 and a fit to allF 2 γ data performed with no constraints on the gluon distribution, then physically unreasonable gluon distributions may result. Our results support recent indications thatQ 0 2 ≤1 GeV2 is too low a value from which to start a perturbative evolution. Starting our evolution atQ 0 2 =5.3 GeV2, we evolve up inQ 2 using a modified version of Rossi's Ansatz. The limited lever arm inQ 2 leads to limited sensitivity to the QCD scale parameter Λ, though there is a preference for low values in the 0.1–0.2 GeV range. We also present new parametrisations of the singular asymptotic quark and gluon distribution functions of the photon which we believe are more accurate than those in current use.  相似文献   

9.
(13)C nuclear magnetic resonance measurements were performed on κ-(BEDT-TTF)(2)Cu(NCS)(2), with the external field placed parallel to the quasi-2D conducting layers. The absorption spectrum is used to determine the electronic spin polarization M(s) as a function of external field H at a temperature T=0.35 K. A discontinuity in the derivative dM(s)/dH at an applied field of H(s)=213±3 kOe is taken as evidence for a Zeeman-driven transition within the superconducting state and stabilization of inhomogeneous superconductivity.  相似文献   

10.
《Nuclear Physics A》1986,449(2):251-255
The observed continuous decrease of the analyzing power for the reactions (p, τX) and (p, αX) on 90Zr and 209Bi at Ep = 72 MeV as a function of the excitation energy of the final nucleus is described by a phenomenological relaxation process.  相似文献   

11.
李登峰  肖海燕  祖小涛  董会宁  高飞 《中国物理 B》2010,19(8):87102-087102
Using first-principles total energy method, we study the structural, the electronic and the magnetic properties of the MnNi(110) c(2×2) surface alloy. Paramagnetic, ferromagnetic, and antiferromagnetic surfaces in the top layer and the second layer are considered. It turns out that the substitutional alloy in the outermost layer with ferromagnetic surface is the most stable in all cases. The buckling of the Mn–Ni(110) c(2×2) surface alloy in the top layer is as large as 0.26á(1á=0.1 n13) and the weak rippling is 0.038 AA in the third layer, in excellent agreement with experimental results. It is proved that the magnetism of Mn can stabilize this surface alloy. Electronic structures show a large magnetic splitting for the Mn atom, which is slightly higher than that of Mn–Ni(100) c(2×2) surface alloy (3.41 eV) due to the higher magnetic moment. A large magnetic moment for the Mn atom is predicted to be 3.81 μB. We suggest the ferromagnetic order of the Mn moments and the ferromagnetic coupling to the Ni substrate, which confirms the experimental results. The magnetism of Mn is identified as the driving force of the large buckling and the work-function change. The comparison with the other magnetic surface alloys is also presented and some trends are predicted.  相似文献   

12.
Gasparov  V. A.  Audouard  A.  Drigo  L.  Schlueter  J. A. 《JETP Letters》2019,110(1):74-78
JETP Letters - We present upper critical magnetic fields data for κ(BEDT-TTF)2Cu[N(CN)2]Br (hereafter k-Br), single crystals with the magnetic field applied either or perpendicular and...  相似文献   

13.
The structural, elastic, and electronic properties of eight intermetallics in Ti–Cu–Me (Me=Al, Ga and In) systems were investigated with the first-principles method. The calculations were performed within the generalized gradient approximation (GGA) with the density functional theory (DFT) using the supercell (SC) method. Calculation results show that the SC approximation is accurate at zero pressure. These intermetallics are classified as stable and metastable in our investigation. The stable phases are those presented in the equilibrium phase diagram at room temperature. The metastable phases are those that usually appear in the equilibrium phase diagram at higher temperatures. The values of calculations show that the TiCuAl, Ti2CuAl5, and TiCu2In compounds are brittle, and the Ti0.5CuAl0.5, TiCu2Al, TiCuGa, Ti2CuGa5, and Ti0.5CuIn0.5 compounds are ductile at zero pressure.  相似文献   

14.
Core level and valence band photoemission spectra of the 124 superconductor ErBa2Cu4O8 are investigated using MgK , HeI, and HeII radiation and compared with photoemission spectra of orthorhombic YBa2Cu3O7 and tetragonal YBa2Cu3O6.2 samples. It is found that the Cu 2p 3/2 core level and the UPS valence band spectra of ErBa2Cu4O8 and YBa2Cu3O7 are very similar but differ significantly from those of YBa2Cu3O6.2. From the resemblance between the ErBa2Cu4O8 and YBa2Cu3O7 spectra it follows that the electronic structures of these two compounds are closely related in spite of an additional CuO chain in the 124 phase. The differences between the YBa2Cu3O6.2 spectra and the other spectra are explained by the the presence of monovalent copper at the crystallographic Cu(1) sites. The Cu 2p 3/2 lineshapes of the here studied superconductors and some CuII compounds are discussed.  相似文献   

15.
Thin films of Cu2O/CuO mixed phase have been deposited on pre-cleaned glass substrate by a spin-coating technique. The influence of Cr-doping, (Cr?+?S) co-doping and the number of coated layers on the structures and optical behaviors of the films were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman, and UV-Visible spectroscopies. From XRD, FTIR and Raman results; the films are composed of polycrystalline monoclinic CuO and cubic Cu2O phases with crystallite sizes ranged from 10.05 to 23.08?nm. Increasing the thickness improves the films’ crystallinity and decreases the defects level in the films. Cr and S incorporation encourages the growth of CuO phase at the expense of Cu2O one and affects the preferred growth direction. The doping with Cr and S blue shifted the Bg mode and multi-phonon transitions. The direct and indirect optical band gaps decreased from 2.25?eV and 1.60?eV to 2.10?eV and 1.20?eV by growing the number of deposited layers from 2 to 8 layers. The film sensitivity towards CO2 at different gas flow rate was studied and compared with those of similar systems. Also; response time, recovery time, detection limit, and limit of quantification are estimated.  相似文献   

16.
The current state of studies presents the effect of ternary addition of transition elements such as Mn, Cr and Si (10 wt%) on the mechanically driven non-equilibrium solubility of 40 wt% Co containing Cu–Co alloy. X-ray powder diffraction analysis indicates that addition of Mn has been found to be the most effective in enhancing the solubility and formation of a complete solid solution between Co and Cu in a short duration (30 h) of ball milling. The microstructure of the ball milled CuCoMn alloy was found to be stable after the isothermal annealing up to a temperature of 450 °C for 1 h. The magnetic properties such as magnetic saturation, coercivity and remanence of ball milled CuCo alloy in the presence of Mn significantly altered after annealing in the temperature range 350–650 °C for 1 h. The best combination of magnetic properties of CuCoMn alloy has been found after annealing at 550 °C for 1 h.  相似文献   

17.
Precision X-ray structural studies were carried out for LiNbO3:Znx single crystals with x=0.0, 2.87, 5.20, and 7.60 at. %. It was found that the insertion of the Zn atoms into the Li position was accompanied by a decrease in the concentration of intrinsic NbLi defects. At x=7.6%, the Zn atoms change their locations in the lattice and partially occupy the Nb positions. This clarifies the structural nature of the “threshold” Zn concentration, which manifests itself as singularities in the concentration dependences of various optical properties. The structural origin of the threshold concentration is likely a common feature of all nonphotorefractive impurities (Mg, Zn, In, and Sc) in LiNbO3. A change in the intrinsic defect structure of the LiNbO3 crystals with different Zn concentrations is discussed.  相似文献   

18.
The room temperature crystal structure of the inverse weberite ZnFeF5 (H2O)2 is refined from powder X-ray diffraction. The cell is orthorhombic (S.G. Imma, a = 7.475(1) →A, b = 10.766(1) →A, c = 6.594(1) →A, z = 4). Below TN = 9(2) K, ZnFeF5(H2O)2 becomes a 1-D antiferromagnet. This behaviour was characterized by susceptibility and magnetization measurements and Mössbauer spectroscopy. On the contrary, isotypic MnFeF5(H2O)2 is confrimed to be a ferrimagnet below Tc = 39.5(1)K. Its magnetic and Mössbauer characteristics are, above and below Tc,and agree with a 3-D magnetic character. Ferrimagnetism could be due to frustration effects as in previously described Fe2F5(H2O)2.  相似文献   

19.
The kinetic of the reactions of the recently synthesized Schiff base (PABST) and its complex with Cu(II) (Cu-PABST) with CN in a 30:70 (v/v) mixture of DMF:water was investigated at pH 6.0 and 10.0, respectively, using multivariate curve resolution alternative least squares (MCR-ALS) method. The effects of different parameters such as volume percent of DMF, pH and surfactants and β-cyclodextrin (β-CD), on observed rate constant of the reactions were investigated. Cetyltrimethylammonium bromide (CTAB) decreased the rate constant of PABST reaction and increased the rate constant of Cu-PABST reaction with CN. Sodium dodecyl sulfate (SDS) and Triton X-100 decreased the rate constant of both reactions. Also the stability constant for the inclusion complexes of PABST and Cu-PABST, and observed rate constants for the reactions of β-CD-PABST and β-CD-Cu-PABST) with CN were determined. β-CD decreased the rate constant of PABST reaction with CN by protecting iminium groups of the Schiff base, while β-CD increased the rate constant of the reaction of Cu-PABST with CN.  相似文献   

20.
叶佳  汪海玲  邓伦华 《中国物理 B》2017,26(10):103102-103102
The high-resolution absorption spectra of the(2, 0),(3, 1), and(8, 5) bands of the A~2Π_u–X~2Σ_g~+system of~(15) N_2~+ have been recorded by using velocity modulation spectroscopy technique in the near infrared region. The rotational constants of the X~2Σ_g~+and A~2Π_u states of~(15) N_2~+ were derived from the spectroscopic data. The isotope shifts of these bands of the A~2Π_u–X~2Σ_g~+system of~(14) N_2~+ and~(15) N_2~+ were also analyzed and discussed.  相似文献   

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