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1.
The study of electrical resistivity of compound-forming liquid alloy, NaPb, is presented as a function of concentration. Hard
sphere diameters of Na and Pb are obtained through the interionic pair potentials evaluated using Troullier and Martinsab initio pseudopotential, which have been used to calculate the partial structure factors S(q). Considering the liquid alloy to be a ternary mixture, Ziman formula, modified for complex formation has been used for calculating
resistivity of binary liquid alloys. Form factors are calculated usingab initio pseudopotentials. The results suggest that Ziman formalism, when used withab initio pseudopotentials, are quite successful in explaining the electrical resistivity data of compound-forming binary liquid alloys. 相似文献
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M.A. Khaleque G.M. Bhuiyan S. Sharmin R.I.M.A. Rashid S.M. Mujibur Rahman 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):319-322
The partial static structure factors, using the Faber-Ziman (FZ) theory, have been calculated for Ag-In alloy. For 20% Ag
at 623 K and 70% Ag at 973 K, the interionic pair potential based on the Bretonnet-Silbert (BS) formalism are calculated and
the hard sphere diameters for the component elements are estimated from the potential profile using the linearised Weeks-Chandler-Andersen
(LWCA) method. The average number densities are calculated on the assumption that the atomic volumes are simply additive.
The calculated structure factors are compared with the experimental values. The partial structure factors for Ag-Ag at 20%
Ag and In-In at 70% Ag appear to be slightly out of phase with the calculated values particularly in large q-region. From the calculations it appears that this discrepancy is related to the process of derivation of the experimental
structure factors from the total one, and the Ag-In alloy can be described by a mixture of hard spheres.
Received 31 October 2001 and Received in final form 10 January 2002 相似文献
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The electrical and thermal resistivities of liquid gallium are calculated over a range of temperatures above the melting point
using the solutions of the Boltzmann equation. The experimental x-ray structure factor of Waseda and the form factor derived
using the Heine-Abarenkov model potential are used in these calculations. The ratio of the electrical and thermal conductivities
is calculated and compared to experimental values and to the theoretical Lorenz number. 相似文献
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Different methods of generating and detecting propagating solitons in uniform and nonuniform, steady and unsteady shearing nematic liquid crystals are proposed, reviewed, and discussed in detail. These include the use of (1) an external plate moving uniformly in the middle and at one end of the liquid crystal (LC) cell, (2) a LC cell with one glass plate moving uniformly and reversing in direction, (3) an external plate as in (1) but moving periodically, (4) pressure gradients along the long axis of the LC cell, (5) circular LC cell with one glass plate rotating, and (6) circular LC cell with radial pressure gradients. In each of these cases, the relevant equations of motion of the LC molecules are derived and analyzed. In the essentially one-deminsional cases of (1) to (3), the governing equation is the damped, driven since-Gorden equation. Analytic and numerical results of single and multisolitons are presented. A multiscale perturbation method is used in the unsteady case of (4). The related case of soliton switch in ferroelectric smecticC
* is discussed.Invited paper presented at Conference on Transport and Propagation in Nonlinear Systems, Los Alamos, May 21–25, 1984. 相似文献
7.
The microscopic structure and dynamics of liquid TixAl1-x alloys together with pure liquid Ti and Al metals were investigated by means of molecular dynamics simulations. This work gives the structural properties, including pair-correlation function, bond-angle distribution function, HA and Voronoi indices, and their composition dependence. The dynamical properties have also been studied. The calculated pair-correlation function, bond-angle distribution function, and HA and Voronoi indices suggest that the stoichiometric composition Ti0.75Al0.25 exhibits a different local structure order compared with other concentrations, which help us understand the appearance of the minimum diffusion coefficient at this composition. These results indicate that the mobility of atoms strongly depends on their atomic local structure. 相似文献
8.
M. B. Shundalov G. A. Pitsevich M. A. Ksenofontov D. S. Umreiko 《Journal of Applied Spectroscopy》2009,76(3):325-333
We present results of ab initio and DFT calculations of the structure, potential functions of the methyl group internal rotation and the amino group inversion,
and vibrational frequencies and intensities in IR and Raman spectra of methylcarbamate. The calculations were carried out
using different basis sets in the HF, MP2, and DFT/B3LYP approximations. The influence of both the basis set size and the
allowance for electronic correlation on peculiarities of the structure of the amino group in methylcarbamate has been analyzed.
It is shown that the B3LYP/6-311++G(2d, p) and B3LYP/cc-pVDZ calculations reproduce highly accurately experimental geometric
parameters of methylcarbamate. Parameters of torsional and inversion potentials and characteristics of vibrational spectra
calculated in different approximations show satisfactory agreement with experimental values.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 349–357, May–June, 2009. 相似文献
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通过X射线衍射、磁测量及正电子湮没谱等手段研究了Tb2AlFe16-xMnx(x=1—8)化合物的结构和磁性.X射线衍射研究结果表明Tb2AlFe16-xMnx化合物具有六角相的Th2Ni17型结构.室温下的正电子湮没实验研究表明,Mn对Fe的替代导致化合物中的铁磁相互作用减弱,并且化合物中存在着较强烈的磁弹耦合效应.磁测量研究结果表明,Mn的替代导致Tb2AlFe16-xMnx化合物的居里温度及自发磁化强度急剧下降.
关键词:
2AlFe16-xMnx化合物')" href="#">Tb2AlFe16-xMnx化合物
磁弹耦合效应
居里温度 相似文献
11.
This paper carries out first principles calculation of the structure,electronic and optical properties of Be x Zn 1 x O alloys based on the density-functional theory for the compositions x = 0.0,0.25,0.5,0.75,1.0.The lattice constants deviations of alloys obey Vegard’s law well.The Be x Zn 1 x O alloys have the direct band gap(Γ-Γ) character,and the bowing coefficients are less than the available theoretical values.Moreover,it investigates in detail the optical properties(dielectric functions,absorption spectrum and refractive index) of these ternary mixed crystals.The obtained results agree well with the available theoretical and experimental values. 相似文献
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P K Khowash 《Pramana》1988,30(3):233-237
A MS Xα SCF method has been initiated to calculate the charge distribution, bonding properties and the density of states in NaLi,
LiMg and LiAl alloys. No ionicity is seen in NaLi but a high covalency of different degree is detected in all the three alloys.
The ionizations potentials calculated are 5.05, 5.5 and 5.58 eV respectively. Comparison with other calculations and experiments
is found to be in fair agreement. 相似文献
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对在较低温度范围的时效处理铁磁形状记忆合金Mn2NiGa的结构、相变和磁性进行了研究.研究发现,母相基体析出了细小的析出相,引起了晶格扭曲和畸变,导致了系统内产生了很大的内应力.在其浓度超过晶格的容忍度之后,提升了体系的马氏体相变温度,使母相在时效温度下转变成马氏体相,并在其中测量到高达900 Oe的矫顽力.由于这种马氏体相的逆相变温度大幅提高,外推获得其居里温度在530 K附近.细小析出相的粗化使内应力消失,样品又回到母相状态.观察到细小析出相粗化的两个阈值温度,分别为423 K和
关键词:
铁磁形状记忆合金
2NiGa')" href="#">Mn2NiGa
时效处理
内应力 相似文献
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采用KKR-CPA-LDA方法研究了不同混乱占位时Fe2CrGa合金基态的电子结构和磁结构. 基态能量表明Fe2CrGa合金更倾向于形成Hg2CuTi型有序结构,而不是L21结构. 能态密度(DOS)分析进一步揭示受晶体场影响的磁性原子内部交换作用是使Fe2CrGa合金形成 Hg2CuTi型有序结构的主要原因.测量了不同热处理所得Fe2CrGa合金的居里温度和分子磁矩, 发现原子占位有序化可以在137K温度范围内调控合金的居里温度.分子磁矩随有序化占位也有相应变化, 分布在2.28μB/f.u.—2.48μB/f.u.之间.理论计算和实验对比可证明Fe2CrGa合金是Hg2CuTi型Heusler合金. 相似文献
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L. Chaveriat C. Meyer D. Beaupre G. Demailly I. Stasik 《Journal of Molecular Liquids》2008,142(1-3):17-21
The mesophasic properties of S-alkylthiohexonolactones (d-galactono- and d-mannono-) and the corresponding itol derivatives with general formula Su-SR (R = C11H23) have been investigated. The observation that the synthesized compounds of this series has been studied using crossed polarized optical microscopy. This study involves the discovery of new chiral Smectic A liquid crystal phase through direct comparison with the defective texture of known Smectic A phase of available commercially biphenyls 8CB and 10CB. 相似文献
18.
ABSTRACTThe present work deals with electronic band structure and derived optical spectra of MgxZn1?xO in the hypothetical rocksalt structure. The computations are performed using full-potential linearised augmented plane wave method. The exchange–correlation potential is described using the Wu-Cohen and Tran-Blaha modified Becke–Johnson generalised gradient approximation (TB-mBJ-GGA). The calculated lattice parameter deviates by less than 1% from experiment showing a net improvement when compared with previous calculations. Moreover, its variation with respect to x does not violate Vegard's law. The TB-mBJ-GGA approach improves the magnitude of the fundamental band gap with respect to experiment. The rocksalt MgxZn1?xO is found to be an indirect gap semiconductor for x?=?0, 0.25, 0.50 and 0.75 and a direct gap semiconductor for x?=?1. The nature of the gap for rocksalt MgxZn1?xO is still in controversy and further investigations are required in this respect. The optical spectra of MgxZn1?xO are analysed and discussed. Our findings yield values of 1.55 and 1.25 for the static refractive index and 2.4 and 1.55 for the static dielectric constant for rocksalt ZnO and rocksalt MgO, respectively. 相似文献
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The crystal structure of deoxyguanosine (5′) phosphate, disodium salt, (5′-dGMP Na2 4H2O) has been determined from three dimensional single crystal x-ray data collected by multiple film, equi-inclination, Weissenberg method using CuKa radiation. The crystal belongs to the monoclinic space groupP21 witha=16.002±0.003 Å,b=10.730±0.003 Å,c=5.575±0.005 Å andβ=101.9°. The structure was solved by symbolic addition method using the program Multan, the reliability index being 0.090. The guanine base is in the usualanti conformation about the C (1′)-N (9) bond withx CN=52.3°. The structure shows two unique conformational features not observed in any nucleotide structure reported so far. The deoxyribose moiety shows O (1′)endo puckering with respect to the best four atom plane defined by C(1′)-C(2′)-C(3′)-C(4′). The conformation about the C(4′)-C(5′) bond isgauche-trans with ø00=62.5° and øoc=174.8°. This is the first nucleotide structure where agt conformer similar to that found in the Watson-Crick double helical DNA model has been experimentally observed. These two conformational features have also direct relevance to the concept of ‘a conformationally rigid nucleotide unit’ developed by Sundaralingam. The nine membered guanine ring is essentially planar. Bases of molecules related by a ‘c’ cell translation tend to overlap, the shortest distance being 3.51 Å between the atoms N (3) and C(8). One of the sodium atoms Na(1) has an octahedral coordination with four water oxygens and O(6) and O(3′) atoms occupying the corners at distances ranging from 2.35 Å to 2.55 Å. 相似文献