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1.
The mechanism of lithium intercalation/deintercalation for phase Al 0.8 Ni 3 Sn 0.2 as anode material used in lithium ion battery was studied carefully based on the first-principle plane wave pseudo-potential method.The calculated results indicated that Sn-Ni-Al alloy had high theoretical capacity when used as anode material,however,there was high initial irreversible capacity loss because of the large volume expansion.Therefore the technological parameters during preparing the Sn-Ni-Al anode should be controlled strictly to make the content of Al 0.8 Ni 3 Sn 0.2 phase as low as possible and to make the anode consist of promising Sn-Ni and Al-Ni phases.For comparison,an experiment based on magnetron sputtering was done.The result showed that the calculation is in good agreement with the experiment.We found that the first-principle investigation method is of far-reaching significance in synthesising new commercial anode materials with high capacity and good cycle performance.  相似文献   

2.
The rapid dendritic growth of primary Ni3Sn phase in undercooled Ni-30.9%Sn-5%Ge alloy is investigated by using the glass fluxing technique. The dendritic growth velocity of Ni3Sn compound is measured as a function of undercooling, and a velocity of 2.47m/s is achieved at the maximum undercooling of 251 K (0.17TL). The addition of the Ge element reduces its growth velocity as compared with the binary Ni75Sn25 alloy. During rapid solidification, the Ni3Sn compound behaves like a normal solid solution and it displays a morphological transition of "coarse dendrite-equiaxed grain-vermicular structure" with the increase of undereooling. Significant solute trapping of Ge atoms occurs in the whole undercooling range.  相似文献   

3.
To reveal the potential aging mechanism for self-irradiation in Pu–Ga alloy, we choose Au–Ag alloy as its substitutional material in terms of its mass density and lattice structure. As a first step for understanding the microscopic behavior of point defects in Au–Ag alloy, we perform a molecular dynamics(MD) simulation on energetics and diffusion of point defects in Au and Ag metal. Our results indicate that the octahedral self-interstitial atom(SIA) is more stable than the tetrahedral SIA. The stability sequence of point defects for He atom in Au/Ag is: substitutional site octahedral interstitial site tetrahedral interstitial site. The He–V cluster(Hen Vm, V denotes vacancy) is the most stable at n = m. For the mono-vacancy diffusion, the MD calculation shows that the first nearest neighbour(1 NN) site is the most favorable site on the basis of the nudged elastic band(NEB) calculation, which is in agreement with previous experimental data. There are two peaks for the second nearest neighbour(2 NN) and the third nearest neighbour(3 NN) diffusion curve in octahedral interstitial site for He atom, indicating that the 2 NN and 3 NN diffusion for octahedral SIA would undergo an intermediate defect structure similar to the 1 NN site. The 3 NN diffusion for the tetrahedral SIA and He atom would undergo an intermediate site in analogy to its initial structure. For diffusion of point defects, the vacancy, SIA, He atom and He–V cluster may have an analogous effect on the diffusion velocity in Ag.  相似文献   

4.
谭霞  王振东  王蕾  樊锡君 《中国物理 B》2010,19(6):64211-064211
Using numerical solution of the full Maxwell-Bloch equations, which is obtained by the finite-difference time-domain method and the iterative predictor-corrector method, we investigate the modulation effect of relative carrier-envelope phase (hereinafter referred to as the relative phase) on resonant propagation of two-colour femtosecond ultrashort laser pulses in a V-type three-level atomic medium. It is found that the pulse splitting occurs for a smaller value of relative phase; when the value of relative phase increases to a certain value, only the variation of pulse shape is present and the pulse splitting does not occur any more; moreover, when the value of relative phase is smaller, the pulse group velocity is larger. The relative phase also has an obvious effect on population and spectral property. Different population transfers can be realized by adjusting the value of relative phase. Generally speaking, for the pulses with smaller areas their spectral strengths and frequency ranges decrease obviously with the value of relative phase increasing; for the pulses with larger areas, with value of the relative phase increasing, their spectral strengths decrease remarkably but the relative strengths of the higher frequency components increase significantly, while the spectral frequency range is not varied evidently.  相似文献   

5.
We investigate the stability,diffusion,and impurity concentration of nitrogen in intrinsic tungsten single crystal employing a first-principles method,and find that a single nitrogen atom is energetically favourable for sitting at the octahedral interstitial site.A nitrogen atom prefers to diffuse between the two nearest neighboring octahedral interstitial sites with a diffusion barrier of 0.72 eV.The diffusion coefficient is determined as a function of temperature and expressed as D(N)=1.66×10~(-7) exp(0.72/kT).The solubility of nitrogen is estimated in intrinsic tungsten in terms of Sieverts’ law.The concentration of the nitrogen impurity is found to be 4.82×10~(-16) A~3 at a temperature of 600 K and a pressure of 1 Pa.A single nitrogen atom can easily sit in an off-vacancy-centre position close to the octahedral interstitial site.There exists a strong attraction between nitrogen and a vacancy with a large binding energy of 1.40 eV.We believe that these results can provide a good reference for the understanding of the behaviour of nitrogen in intrinsic tungsten.  相似文献   

6.
The application of high pressure can fundamentally modify the crystalline and electronic structures of elements as well as their chemical reactivity, which could lead to the formation of novel materials. Here, we explore the reactivity of lithium with sodium under high pressure, using a swarm structure searching techniques combined with first-principles calculations, which identify a thermodynamically stable Li–Na compound adopting an orthorhombic oP8 phase at pressure above 355 GPa. The formation of Li–Na may be a consequence of strong concentration of electrons transfering from the lithium and the sodium atoms into the interstitial sites, which also leads to open a relatively wide band gap for Li NaoP8. This is substantially different from atoms sharing or exchanging electrons in common compounds and alloys. In addition, lattice-dynamic calculations indicate that Li Na-oP8 remains dynamically stable when pressure decompresses down to 70 GPa.  相似文献   

7.
We report a detailed ab initio study of the trapping behavior of interstitial helium atoms (IHAs) in hcp Ti. The tetrahedral interstitial site for one He is confirmed to be the most stable IHA configuration, but the most favorable interstitial site comprises two adjacent octahedral sites for two helium atoms. The octahedral IHA can trap another IHA regardless of the site where it is initially located, whereas the tetrahedral IHA cannot. Hybridization among the different states is responsible for the stable order, which has significant implications for He clustering and bubble nucleation that can affect material performance in future fusion reactors. These results provide the basis for the development of improved atomistic models.  相似文献   

8.
Molybdenum ions are implanted into aluminium with high ion flux and high dose at elevated temperatures of 200℃, 400℃ and 500℃. Due to the high temperature and high flux of vacancies and interstitial atoms, the atom diffusion and chemical effects are enhanced during the ion implantation. The effects increase with increasing ion flux and dose, so that new phase formation and phase transition emerge noticeably. X-ray diffraction analysis shows that when the aluminium is implanted with Mo ions at a low ion flux (25μA/cm2), the Al5Mo alloy is formed. The atomic ratio of Mo/Al of the Al5Mo phase is close to 20%. When the aluminium is implanted with Mo ions at a high ion flux (50μA/cm2), the phase transition from Al5Mo to Al12Mo appears, and the latter is dominant, which is determined to be the final phase. The ratio of Mo/Al in Al12Mo is 7.7%. Rutherford backscattering spectroscopy indicates also that the Mo/Al atom ratio is ~7% to ~8% in Mo-implanted aluminium. The atomic ratios of the constituents in Al5Mo and Al12Mo are of stoichiometric composition for these alloys. The thicknesses of the Al12Mo alloy layers for Mo-implanted Al with ion doses of 3×1017/cm2 and 1×1018/cm2 are 550nm and 2000nm, respectively. The pitting corrosion potential Vp increases obviously. It is clear that due to the formation of Al12Mo alloy layer, the pitting corrosion resistance is enhanced.  相似文献   

9.
This paper discusses the amplitude-squared squeezing for the superposition of two coherent states with their phase differences being separately π/2, 3π/2, and π1, as well as for the superposition state of two pseudoclassical states. According to the analysis, it is found that the superposition state of two coherent states with their phase differences π/2 and 3π/2, and the superposition state of two pseudoclassical states both do exhibit the amplitude-squared squeezing. Also, some specific states are found to exhibit even stronger squeezing effects when relative phase of the superposition is equal to the average photon number. Amplitude-squared squeezing is dependent on the difference in phase between two coherent states.  相似文献   

10.
We investigated the nonsequential double ionization(NSDI) in Ar by two-color elliptically polarized laser field with a three-dimensional(3D) classical ensemble method. We study the relative phase effect of NSDI and distinguish two particular recollision channels in NSDI, which are recollision–impact ionization(RII) and recollision-induced excitation with subsequent ionization(RESI), according to the delay-time between the recollision and the final double ionization. The numerical results indicate that the ion momentum distribution is changed and the triangle structure is more obvious with the decrease of the relative phase. We also demonstrate that the RESI process always dominates in the whole double ionization process and the ratio of RESI and RII channels can be influenced by the relative phase.  相似文献   

11.
This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVOquasi-phase-matching, intracavity optical parametric generator, periodically poled MgO-doped lithium niobate (PPMgLN)Project supported by the National Natural Science Foundation of China (Grant Nos 10474071 and 60671036).4265K, 4260F, 4270This paper demonstrates a compact efficient optical parametric generator internal to a Q-switched diode-end-pumped Nd:YVO$_{4}$ laser with periodically poled MgO:LiNbO3(PPMgLN). With the Q-switch set at a repetition rate of 25kHz and the PPMgLN crystal operated at room temperature (25\du\,), the intracavity optical parametric generator threshold was reached as a diode pump power of 0.9\,W. A maximum signal output power of 0.34W with a pulse width of 25\,ns and a beam quality factor of 1.4 was obtained at an incident diode power of 3.4\,W, leading to a conversion efficiency of 10{\%} with a slope efficiency of 14.4{\%}. By varying the crystal temperature from 25 to 200\du, the output signal wavelengths were tuned in range of 1506--1565\,nm. Over a 30-minutes interval, the instability of the signal power was measured to be less than 1{\%}. In addition, the threshold pump intensity for the intracavity optical parametric generator is theoretically investigated, and the obtained result is in good agreement with the experimental results.  相似文献   

12.
尹亚玲  夏勇  印建平 《中国物理 B》2008,17(10):3672-3677
We propose a promising scheme to decelerate a CW molecular beam by using a red-detuned quasi-cw semi-Gaussian laser beam (SGB). We study the dynamical process of the deceleration for a CW deuterated ammonia (ND3) molecular beam by Monte-Carlo simulation method. Our study shows that we can obtain a ND3 molecular beam with a relative average kinetic energy loss of about 10% and a relative output molecular number of more than 90% by using a single quasi-cw SGB with a power of 1.5kW and a maximum optical well depth of 7.33mK.  相似文献   

13.
於黄忠  彭俊彪 《中国物理 B》2008,17(8):3143-3148
This paper studies the self-organization of the polymer in solar cells based on poly(3-hexylthiophene): [6, 6]-phenyl C61-butyric acid methyl ester by controlling the growth rate of active layer. These blend films are characterized by UV-vis absorption spectroscopy, charge-transport dark J - V curve, x-ray diffraction pattern curve, and atomic force microscopy. The results indicate that slowing down the drying process of the wet films leads to an enhanced selforganization, which causes an increased hole transport. Increased incident light absorption, higher carrier mobility, and balanced carrier transport in the active layer explain the enhancement in the device performance, the power conversion efficiency of 3.43% and fill factor up to 64.6% are achieved under Air Mass 1.5, 100 mW/cm^2.  相似文献   

14.
This paper studies the equilibrium structure parameters and the dependences of the elastic properties on pressure for rutile TiO2 by using the Cambridge Serial Total Energy Package (CASTEP) program in the frame of density functional theory. The obtained equilibrium structure parameters, bulk modulus B0 and its pressure derivative B′0 are in good agreement with experiments and the theoretical results. The six independent elastic constants of rutile TiO2 under pressure are theoretically investigated for the first time. It is found that, as pressure increases, the elastic constants C11, C33, C66, C12 and C13 increase, The variation of elastic constant C44 is not obvious and the anisotropy will weaken.  相似文献   

15.
This paper reports that high quality CuGeO3 single crystals were successfully grown by floating-zone technique and the magnetic property was studied. The temperature dependence of magnetic susceptibility below the spin-Peierls (SP) transition temperature (Tsp) under magnetic fields applying along both the a- and c-axis direction can be fitted well by a model of noninteracting dimmers. The spin gap derived from the fitting is consistent with other reports. There is a very weak anisotropy in the fitting parameters for different directions, which should be expected from a SP system. A small upturn in susceptibility at low temperature due to paramagnetic impurities and/or defects can be observed. A suppression of the upturn by magnetic field is first discovered in this system and the possible origins for this suppression are discussed.  相似文献   

16.
This paper reports that the YBa2Cu3-xZnxO7-δ (x = 0-0.4) samples are researched by means of x-ray diffraction, calculations of binding energy, the positron experiments and variations of oxygen content. The results of simulated calculations, positron experiments and variations of oxygen content support the existence of cluster effect. Moreover, it is concluded that the cluster effect is an important factor on suppression of high-Tc cuprate superconductivity and the Tc does not depend on the density of valence electron directly.  相似文献   

17.
闫冰  潘守甫 《中国物理 B》2008,17(4):1501-1505
This paper performs multi-reference second-order perturbation theory calculations on the ground state and a number of low-lying excited states of HSCH3 molecule, and calculates the vertical excitation energies and low-energy potential-energy curves, based on which the photodissociation channels of HSCH3 at 193,222,248 nm are clarified.  相似文献   

18.
This paper studies the equilibrium geometries and electronic properties of Ben and BenLi clusters, up to n=15, by using density-functional theory(DFT) at B3LYP/6-31G(d) level. The lowest-energy structures of Ben and BenLi clusters were determined. The results indicate that a single lithium impurity enhances the stability and chemical reactivity of the beryllium clusters. It finds that the geometries of the host clusters change significantly after the addition of the lithium atom for n ≥8. The lithium impurity prefers to be on the periphery of beryllium clusters, and occupies vertex sites. Both Be4Li, Be9Li, and Be13Li were found to be particularly stable with higher average binding energy, local peaks of second-order energy difference and fragmentation energies. For all the BenLi clusters studied, we found charge transfers from the Li to Be site and co-existence of covalent and metallic bonding characteristics.  相似文献   

19.
First-principles investigation of BAs and BxGa1-xAs alloys Using first-principles calculations in the generalized gradient approximation, the electronic properties of BAs and BxGa1-xAs alloys are studied. At the Brillouin-zone centre, the lowest conduction band is the three-degenerate p-like Г15c state rather than s-like Г1c state, and the conduction band minimum (CBM) is along the A line between the Г and X points-at approximately 11/14(1,0,0)2π/a. With boron content at 0%-18.75%, BxGa1-xAs alloys have a small (2.6 eV) and relatively composition-independent band-gap bowing parameter, the band-gap increases monotonically by -18meV/B% with increasing boron content. In addition, the formation enthalpies of mixing for BxGa1-xAs alloys with boron content at 6.25% and 12.5% are calculated, and the large formation enthalpies may explain the difficulty in alloying boron to GaAs.  相似文献   

20.
张毅  邓朝勇  马静  林元华  南策文 《中国物理 B》2008,17(10):3910-3916
Multiferroic NiFe2O4 (NFO)-BaTiO3 (BTO) bilayered thin films are epitaxially grown on (001) Nb-doped SrTiO3 (STO) substrates by pulsed-laser deposition (PLD). Different growth sequences of NFO and BTO on the substrate yield two kinds of epitaxial heterostructures with (001)-orientation, i.e. (001)-NFO/(001)-BTO/substrate and (001)- BTO/(001)-NFO/substrate. Microstructure studies from x-ray diffraction (XRD) and electron microscopies show differences between these two heterostructures, which result in different multiferroic behaviours. The heterostructured composite films exhibit good coexistence of both ferroelectric and ferromagnetic properties, in particular, obvious magnetoelectric (ME) effect on coupling response.  相似文献   

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