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1.
The Hall coefficient (RH) of polycrystalline Yb showing the f.c.c.-h.c.p. transformation has been determined at 20 koe in the range 1.8–420°K. Both the structural and the associated magnetic transformation would separately be expected to modify RH, but the evidence suggests that the observed behaviour through the transition arises primarily from the effects of the change in structure. A more detailed interpretation is presently not possible, however, because of the lack of knowledge of the band structure of h.c.p. Yb. 相似文献
2.
The Néel temperature TN of f.c.c. stainless steel has been measured as a function of pressure using the Mössbauer effect. A sample with approximately 74 wt.% Fe, doped with 57Co, and having TN = 58.4 ± 0.1 K at zero pressure, shows TN rising with pressure with increasing slope. Our results indicate that TN is raised to room temperature by a pressure of 175 ± 5 kbar. 相似文献
3.
The superconducting transition temperature (Tc) has been measured before and after the introduction of hydrogen into Nb(1?x)Rux. In all cases, the presence of appreciable amounts of this interstitial component led to a sharp increase in the Tc. All the evidence suggests that conversion of the host metal lattice to f.c.c. is necessary for the appearance of the elevated Tc. 相似文献
4.
The asphericity of 3d-electrons was measured as a function of temperature in some f.c.c. ferromagnetic Co alloys by means of the polarized neutron technique. The asphericity, as measured by the population of the eg and t2g sub-levels, was found to be almost independent of temperature. Simple models failed to explain the data. 相似文献
5.
A new calculation of the induction (crystal field) energy of the f.c.c. and h.c.p. structures of the rare-gas crystals of neon and argon gives an energy in favour of f.c.c. which is more than sufficient to counter the summed pair-potential which favours h.c.p. Predicted values of (E f.c.c. - E h.c.p.)/E f.c.c. for neon and argon are 0·9 × 10-3 and 1·3 × 10-3 respectively. These values are similar to those that have been obtained for a modified dispersion energy and it is concluded that they should be added to these dispersion energies. Calculations on solid helium show a negligible difference in the induction energy for the two close-packed structures. 相似文献
6.
APW-Xα calculations of a f.c.c.-b.c.c. phase transition in Xe prior to metallization give P ? 950 kbar, contrary to the 820 kbar result of Hama and Matsui; their use of non-touching APW spheres (f.c.c.) may be the crucial difference. Hartree-Fock plus correlation calculations in Kr indicate that f-bands play no role in rare gas crystal metallization. 相似文献
7.
The mean-square displacements of volume atoms, surface atoms and atoms near a vacancy are calculated for f.c.c. metals and rare gas solids, using a simple series expansion of the Wallis formula. We employ a model with rotationally invariant bond bending forces, unlike the de Launay model used by Masri and Dobrzynski. For atoms near a vacancy and for rare gas solids this method has been applied for the first time. The calculations are done to the R4 term in the expansion. The inclusion of the R4 term together with temperature-dependent elastic constants give results which are in better agreement with experiment. For rare gas solids Lindemann ratios calculated by this method agree closely with the values obtained from elaborate computations as well as those deduced from entropy data. The present calculation also supports the view that the melting of solids is initiated at the crystal surfaces and in the neighbourhood of vacancies. 相似文献
8.
《Solid State Communications》1986,57(4):277-281
We propose experimental evidences for the sd character of the occupied band states of f.c.c. Yb metal. Photoionization cross-section σ1 in the range 24–65 eV, covering the 5p core electron energies have been measured for both Yb (4ƒ146s25d0) and Lu (4ƒ146s25d1). Both the hv dependence of σ1 for the Yb valence band and the presence of photoemission resonances above the 5p edges of Lu and Yb indicate the presence of occupied 5d states at the top of the valence band of solid Yb. The Yb 4ƒ σ1 is presented in order to distinguish the 5d band resonances from the 5p-5d giant dipole autoionization decays. L2, 3 X-ray absorption white lines for Yb provide a measure of the 5d bandwidth. 相似文献
9.
The a.c. conductivity of semiconducting cis-cisoid polyphenylacetylene (PPA) pellets has been studied at temperatures between 230 and 290 K and frequencies, ?, from 37 to 105 Hz. The a.c. conductivity (σa.c.) is found to be strongly temperature dependent. σa.c. is proportional to ?s with s varying from 0.45 to 0.75 as temperature is raised from 230 to 290 K. Both frequency dispersion and strong temperature dependence of σa.c. are best explained by the mechanism of hopping conduction in the band-tails. 相似文献
10.
When Nb3Au is converted from the A-15 structure to the b.c.c. allotrope, a sharp decrease in the superconducting transition temperature, Tc, occurs (11.1 to 1.5 K). To study possible causes for this sharp decrease, specific heat measurements have been made on the b.c.c. form of Nb3Au yielding values of γ=19.2 mJ/mole-K2, β=0.274 mJ/mole-K4 and θD=305 K. These parameters compared with published values for the A-15 Nb3Au indicate that a sharp drop in the density of states at the Fermi level, N(0), occurs when the A-15 structure is converted to the b.c.c. form. 相似文献
11.
Inelastic neutron scattering measurement of stiffness constant D on simple crystals of disordered f.c.c. Ni-Mn alloys has been performed at differen Mn concentrations (1.5%, 6%, 12%, 18% at.Mn). Stiffness constant D show similar behaviour vs concentration as observed in Ni-Fe alloys by Hennion et al. [Solid State Commun.17, 899 (1975)]. This behaviour does not agree with that observed by inelastic small-angle magnetic scattering measurements by Menshikov et al. [Int. J. Magn.1, 91 (1975)]. A noticeable enhancement of the spin-wave width is also observed at higher Mn content and higher spin wave energies. The values of pair exchange integrals are also given. 相似文献
12.
L. Tichý H. Tichá M. Frumar J. Klikorka A. Tříska Č. Barta A. Němečková 《Czechoslovak Journal of Physics》1982,32(12):1363-1373
The spectral dependence of the index of refraction (n) in Ge40?xSbxS60 glasses has been described by a simple one-oscillator approximation using the Wemple-DiDomenico treatment (W-D). The possibility of application of the Moss formula or W-D in some amorphous materials for estimation of the optical gap (E g) fromn or vice versa has been examined. From the results of optical and d.c. electrical conductivity measurements and bond statistics suggestions it can be concluded that many types of defect states are created in Ge40?xSbxS60 glasses, which pin the Fermi level in the vicinity ofE g/2. 相似文献
13.
Electroluminescent (EL) film panels of ZnS: Mn, Cu, Cl operated by a.c. electric field are studied at room temperature. The emission spectrum consists of a single peak at 590 nm. The EL emittance B varies with frequency f of the applied a.c. electric field as B = Bs ? Bm exp ? f/fc where Bs, Bm and fc are constants. This equation indicates that B approaches a saturation value Bs when f?fc and a linear relation between B and f when f?fc. At a fixed frequency f, B is found to depend on the applied voltage V as B = A exp [-G/F + V)] where A, G and F are constants. This formula is valid at all stages of the operating life of the film panel. 相似文献
14.
M. Kogachi 《Journal of Physics and Chemistry of Solids》1973,34(1):67-75
Expressions of the band-structure energy and the electrostatic energy characterized by the usual long-range and short-range order parameters are given to a binary alloy of simple metals with the f.c.c.-type or b.c.c.-type structure.The ordering energy and the local ordering energy are calculated for the InMg, LiMg and AlZn systems. The numerical results explain successfully the facts that the InMg system has the Ll0-type and Ll2-type ordered phases, each of which exists over a wide range of concentration and that the LiMg system has a local order with a negative short-range order parameter, while the AlZn system has that with the positive one. A lattice distortion in the Ll0-type ordered structure of InMg is also discussed. 相似文献
15.
Masaaki Yamagishi 《Journal of Quantitative Spectroscopy & Radiative Transfer》1976,16(7):587-593
An equation for the intensity ofO(33P?33S) at 8446 A and ofO(35P?35S) at 7771 A has been derived as a function of electron-, Ar- and O2-densities assuming applicability of the excitation processes proposed by Bennett et al. and by Tunitskii and Cherkasov. The electron temperature has been assumed to be constant. The results are compared with experimental data obtained in the d.c. glow discharge of Ar-O2 mixtures. 相似文献
16.
The coherent potential approximation has been extended in order to treat the case of multiple bands in ferromagnetic substitutional binary alloys. The concentration dependence of total magnetic moments and their aspherical contribution, eg and t2g, were derived and compared with experimental data in Co-Ni f.c.c. alloys. 相似文献
17.
The dark d.c. conductance of thin films of copper complexes of phthalocyanine (α-form), hemiporphyrazine and dihydrodibenzo [b, i] [1, 4, 8, 11] tetra-azacyclotetradecine has been studied in vacuo and in the presence of an extensive range of gases. Only those gases which can be classed as electron acceptors increased the conductance, with NO2/N2O4 (“NOX”) being particularly effective. Spectroscopic evidence is provided to show that the NOX-copper phthalocyanine interaction generates the organic radical cation and NO-2, and that substantial quantities of gas are accumulated within the thin film. A new class of extrinsic organic semiconductor is described. 相似文献
18.
《Current Applied Physics》2010,10(4):1013-1016
The LiCoVO4 compound is synthesized by solution-based chemical method. X-ray diffraction analysis exhibits a single phase nature of the compound with cubic structure. The dielectric constant (εr), tangent loss (tanδ) and a.c. conductivity (σac) have been studied as a function of frequency and temperature using complex impedance spectroscopy (CIS) technique. The variation of (εr and tanδ) with frequency at studied temperatures shows a dispersive behavior at low frequencies. Frequency dependence of σac at different temperatures obeys Jonscher’s universal power law governed by the relation: σac = σdc + Aωn, where n is the frequency exponent in the range of 0 ⩽ n ⩽ 1 and A is a constant that depends upon temperature. 相似文献
19.
Effective pair interactions for binary f.c.c. transition metal alloys have been computed using a generalized perturbation method starting from the completely disordered state. Their properties, as a function of interatomic distance, band filling, disorder and concentration are discussed. The ordering energy computed from the pair interactions is succesfully compared, for the Cu3Autype structure, to the energy derived from the band structure determined by the recursion method. 相似文献
20.
Masaaki Yamagishi 《Journal of Quantitative Spectroscopy & Radiative Transfer》1978,20(1):121-127
Measurements have been made of intensities of the spectral lines emitted from an Ne-O2 d.c. discharge with small discharge current (1–4 mA) under the following conditions: gas pressures of 2 and 3 torr and oxygen partial pressures (P02) up to 0.1 torr. All of the Ne(I) line intensities observed decrease when O2 is added. The Ne(I) λ5852 line (1s2-2p1) has been studied in detail as a representative example. The population density of the 2p1 level of neon has been obtained from the intensity measurements as a function of P02. The energy-distribution function of electrons has been determined using Druyvesteyn's method in order to calculate the population density for a corona model. The high-energy tail of the measured distribution function is markedly reduced when O2 is added. It is shown that inelastic collisions of electrons with O2 produce large energy losses for the electrons. These cause a decrease in population density of the 2p1 level when O2 is added. The population density of the 2p1 level at a gas pressure of 2 torr is 1.2×104 cm-3 in pure neon and 5.2×102 cm-3 in an Ne-O2 mixture (P02 = 0.01 torr). The electron densities and average electron energies are 3.5×108 cm-3 and 8.7 eV and 1.7×108 cm-3 and 5.3 eV, respectively, for the specified two cases. 相似文献