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31.
The atomic configurations of liquid and glassy Mg65Cu25Y10 alloy have been simulated in the temperature range of 300 K to 2000 K via ab initio molecular dynamics. The variations of pair correlation function (PCF), structure factor (SF), coordination number (CN) and bond pairs with the temperature for this alloy are characterized. It has been shown that the atoms are near densely packed and icosahedral type of short-range order (SRO) is predominant in the glass state. Icosahedral medium range order (MRO) can be formed by vertex or intercross connection of icosahedral SROs. In this work, an icosahedral MRO which is composed of 55 atoms has been found. It has been also clarified that Mg and Cu occupy the centre or vertex, and Y atoms only occupy the vertex of the icosahedron in this glassy alloy. It is believed that these findings have implication for understanding the glass forming mechanism of magnesium based metallic glasses. 相似文献
32.
S. I. Anisimov N. A. Inogamov Yu. V. Petrov V. A. Khokhlov V. V. Zhakhovskii K. Nishihara M. B. Agranat S. I. Ashitkov P. S. Komarov 《Applied Physics A: Materials Science & Processing》2008,92(4):939-943
The developed model including hydrodynamics with electron heat conduction and electron–ion energy exchange, and cavitation
breakup of stretched metastable liquid aluminum (Al) is compared with our laser experiments. For the first time the measured
and calculated ablation thresholds agree well in both crater depth and fluence. 相似文献
33.
Michael Burgess 《Journal of Non》2008,354(29):3491-3502
Packing is an intrinsic property of glass, defined as the ratio of ionic volume to molar volume, and is a useful parameter for analyzing structural changes with composition. Alkali based glasses show two trends in packing, one dominated by the oxygen covalent network for the small ions, Li and Na, and one ionically dominated by the metal cations for the large, K, Rb and Cs cases [S. Giri, C. Gaebler, J. Helmus, M. Affatigato, S.A. Feller, J. Non-Cryst. Solids 347 (2004) 87]. We have found that alkaline earth glasses do not display these behaviors, and in this paper we determined the packing fractions of these glasses and compared them with the alkali case. Further, we considered the structural implications of the packing trends. 相似文献
34.
Duk-Yong Choi Steve Maden Andrei Rode Rongping Wang Barry Luther-Davies 《Journal of Non》2008,354(27):3179-3183
Chalcogenide glasses are good candidate materials for ultra-fast non-linear optic devices. In this work, we present the photolithographic process and the plasma etching of arsenic tri-sulphide (As2S3) film. The films were deposited on thermally oxidized silicon substrates by ultra-fast pulsed laser deposition. To protect As2S3 film from photo-resist developer, thin resist layer ∼100-200 nm was remained on the UV exposed area by controlling resist development time. After removing the protective layer in oxygen plasma, As2S3 waveguides were patterned in inductively coupled plasma reactive ion etching (ICP-RIE) system using CF4-O2 gas mixture. We investigated the etch rate and the etch selectivity to photo-resist of As2S3 as a function of bias power, induction power, operating pressure, and gas flow rate ratio of CF4 and O2. The film is mainly etched by the chemical reaction with fluorine radicals. The content of oxygen in the plasma determines the etched sidewall profiles and nearly vertical profile was obtained at high oxygen content plasma. 相似文献
35.
G. Kuri 《Applied Physics A: Materials Science & Processing》1999,68(6):699-703
Analytical electron microscopy, high-resolution X-ray diffraction and combined Rutherford backscattering spectrometry and
channeling experiments have been used to investigate the radiation damage and the effect of post-implantation annealing on
the microstructure of GaAs(100) single crystals implanted with 1.00 MeV Cu+ ions to a dose of ≈ 3×1016 cm-2 at room temperature. The experiments reveal the formation of a thick and continuous amorphous layer in the as-implanted state.
Annealing up to 600 °C for 60 min does not result in the complete recovery of the lattice order. The residual disorder in
GaAs has been found to be mostly microtwins and stacking fault bundles. The redistribution of implanted atoms during annealing
results in the formation of nano-sized Cu particles in the GaAs matrix. The X-ray diffraction result shows a cube-on-cube
orientation of the Cu particles with the GaAs lattice. The depth distribution and size of the Cu particles have been determined
from the experimental data. A tentative explanation for these results is presented.
Received: 15 February 1999 / Accepted: 18 February 1999 / Published online: 28 April 1999 相似文献
36.
18Ni-maraging steel has been entirely nanocrystallized by a series of processes including solution treatment, hot-rolling deformation, cold-drawn deformation and direct electric heating. The plasma nitriding of nanocrystallized 18Ni-maraging steel was carried out at 410 °C for 3 h and 6 h in a mixture gas of 20% N2 + 80% H2 with a pressure of 400 Pa. The surface phase constructions and nitrogen concentration profile in surface layer were analyzed using an X-ray diffractometer (XRD) and the glow discharge spectrometry (GDS), respectively. The results show that an about 2 μm thick compound layer (mono-phase γ′-Fe4N) can be produced on the top of the surface layer of nanocrystallized 18Ni-maraging steel plasma nitrided at 410 °C for 6 h. The measured hardness value of the nitrided surface is 11.6 GPa. More importantly, the γ′-Fe4N phase has better plasticity, i.e., its plastic deformation energy calculated from the load-displacement curve obtained by nano-indentation tester is close to that of nanocrystallized 18Ni-maraging steel. Additionally, the mechanical properties of γ′-Fe4N phase were also characterized by first-principles calculations. The calculated results indicate that the hardness value and the ratio of bulk to shear modulus (B/G) of the γ′-Fe4N phase are 10.15 GPa and 3.12 (>1.75), respectively. This demonstrates that the γ′-Fe4N phase has higher hardness and better ductility. 相似文献
37.
K. Ragavendran 《Physica B: Condensed Matter》2009,404(2):248-250
Density functional theory is used to understand the response of the transition metal-oxygen octahedra in LixMn2O4 and LixNi0.5Mn1.5O4 to lithium intercalation and de-intercalation. Electronic structure computations on these compounds for x=0, 0.5 and 1 indicate that the 3d DOS of Mn is almost unaffected to variations in x. On the other hand, the oxygen 2p-DOS and to a lesser extent Ni 3d DOS are found to be sensitive to perturbation. The observations are explained on the grounds of self-regulating response, characteristic of systems having localized d states that communicate with a covalent manifold. 相似文献
38.
D. A. Drabold 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):1-21
In this Colloquium, I describe some current frontiers in the physics of semiconducting amorphous materials and glasses, including
a short, but self-contained discussion of techniques for creating computer models, among them the quench from the melt method,
the Activation-Relaxation Technique, the decorate and relax method, and the experimentally constrained molecular relaxation
scheme. A representative study of an interesting and important glass (amorphous GeSe3:Ag) is provided. This material is a fast-ion conductor and a serious candidate to replace current FLASH memory. Next, I discuss
the effects of topological disorder on electronic states. By computing the decay of the density matrix in real space, and
also computing well-localized Wannier functions, we close with a quantitative discussion of Kohn’s Principle of Nearsightedness in amorphous silicon. 相似文献
39.
Molecular Dynamics Study of Stability of Solid Solutions and Amorphous Phase in the Cu-Al System
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The relative stability of fee and bcc solid solutions and amorphous phase with different compositions in the Cu-Al system is studied by molecular dynamics simulations with n-body potentials. For CU1-xAlx alloys, the calculations show that the fee solid solution has the lowest energies in the composition region with x 〈 0.32 or x 〉 0.72, while the bcc solid solution has the lowest energies in the central composition range, in agreement with the ball-milling experiments that a single bcc solid solution with 0.30 〈 x 〈 0.70 is obtained. The evolution of structures in solid solutions and amorphous phase is studied by the coordination number (CN) and bond-length analysis so as to unveil the underlying physics. It is found that the energy sequence among three phases is determined by the competition in energy change originating from the bond length and CNs (or the number of bonds). 相似文献
40.
We analyse one-loop radiative corrections to the inflationary potential in the theory, where inflation is driven by the Standard Model Higgs field. We show that inflation is possible provided the Higgs mass mH lies in the interval mmin<mH<mmax, where mmin=[136.7+(mt−171.2)×1.95] GeV, mmax=[184.5+(mt−171.2)×0.5] GeV and mt is the mass of the top quark. In the renormalization scheme associated with the Einstein frame the predictions of the spectral index of scalar fluctuations and of the tensor-to-scalar ratio practically do not depend on the Higgs mass within the admitted region and are equal to ns=0.97 and r=0.0034 correspondingly. 相似文献