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1.
Based on the synchroshear mechanism, the formation of intrinsic stacking fault I 2 and twin-like stacking fault T 2 in C14 Laves phases has been modeled in detail and the generalised stacking fault energy curve of I 2 and T 2 for C14 Laves phase MgZn2 has been calculated from first-principles. The results demonstrate that the unstable stacking fault energy of I 2 by synchroshear is still very large, and the stable stacking fault energy of I 2 is higher in comparison with pure Mg implying that the formation of I 2 stacking fault in MgZn2 is difficult. Starting with the I 2 configuration, the T 2 stacking fault can be formed by an additional synchroshear. The unstable and stable stacking fault energies of T 2 are only slightly larger than those of I 2, implying that the formation of T 2 may be essentially similar to that of I 2. From the obtained generalised stacking fault energy, the relevant deformation mechanism of MgZn2 is also discussed. Finally, the electronic structure during synchroshear process is further studied. 相似文献
2.
The potential of nuclear magnetic resonance two-dimensionalT
1-T
2 correlation spectroscopy for quality control in food science is explored for three types of food, namely, egg (white and
yolk), cellular tissue (fruit and vegetable) and hydrocolloids (creams and baked products). The complications of cross-relaxation
and diffusive exchange are highlighted and various tools for peak assignment are discussed. 相似文献
3.
In G-rich DNA, it is well known that the form changes from single-strand DNA to G-quadruplex due to cations. In this study, we analyze the diffusion coefficient and fluorescence intensity obtained by fluorescence correlation spectroscopy for short G-rich DNA of the (G3T1)4 sequence labeled as 5-Carboxytetramethylrhodamine (TAMRA) with variation of the K+ ion concentration. At a K+ ion concentration of more than 200 mM, the single-strand DNA was changed to the G-quadruplex. The size of the G-quadruplex decreased to 86% than the size of the single strand DNA at K+ ion concentration of 0 M. The size of the G-quadruplex and the fluorescence intensity of TAMRA attached to the DNA were constant with an increase in the K+ ion concentration between 200 and 800 mM. This means that the size of the DNA and the fluorescence intensity of the TAMRA are not affected by the K+ ion concentration at the G-quadruplex structure because the binding structure of DNA and TAMRA dye leads to stability at a concentration of less than 100 mM K+. Based on our short G-rich DNA results, longer G-rich DNA is analyzed for the diffusion coefficient of the DNA and the fluorescence intensity variation of fluorescence dye attached to the DNA. 相似文献
4.
A model Hamiltonian for B cation ordering (Sc-Nb(Ta)) in PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3 solid solutions is constructed. The parameters of the model Hamiltonian are determined from the ab initio calculation within the ionic crystal model with allowance made for the deformability and the dipole and quadrupole polarizabilities of the ions. The temperatures of the phase transition due to the ordering of the B cations are calculated by the Monte Carlo method in the mean-field and cluster approximations. The phase transition temperatures calculated by the Monte Carlo method (1920 K for PbSc1/2Ta1/2O3 and 1810 K for PbSc1/2Nb1/2O3) are consistent with the experimental data (1770 and 1450 K, respectively). The thermodynamic properties of the cation ordering are investigated using the Monte Carlo method. 相似文献
5.
G. A. Komandin A. S. Prokhorov V. I. Torgashev E. S. Zhukova B. P. Gorshunov A. A. Bush 《Physics of the Solid State》2011,53(4):736-744
The spectra of complex permittivity of a Ba2Mg2Fe12O22 single crystal belonging to the family of Y-type hexaferrites have been measured over a wide temperature range (10–300 K) with the aim of determining the dynamic parameters
of the phonon and magnetic subsystems in the terahertz and infrared frequency ranges (3–4500 cm−1). A factor-group analysis of the vibrational modes has been performed, and the results obtained have been compared with the
experimentally observed resonances. The oscillator parameters of all nineteen phonon modes of E
u
symmetry, which are allowed by the symmetry of the Ba2Mg2Fe12O22 crystal lattice, have been calculated. It has been found that, at temperatures below 195 and 50 K, the spectral response
exhibits new absorption lines due to magnetic excitations. 相似文献
6.
L. S. Lobanovskii V. M. Novotortsev S. F. Marenkin V. M. Trukhan T. V. Shelkovaya 《JETP Letters》2009,89(7):333-336
The magnetic and electric properties of a Cd0.90Mn0.10GeAs2 solid solution with the chalcopyrite structure have been investigated in wide temperature and field ranges. It has been found that a metamagnetic transition from a low-magnetization state to a high-magnetization one is initiated in Cd0.90Mn0.10GeAs2 near the magnetic ordering temperature. This transition is accompanied by the hysteresis of magnetic properties. An external magnetic field at temperatures above T C also induces the metamagnetic transition. When the temperature increases above T C, the magnetization jump decreases, whereas fields inducing the metamagnetic transition increase. The band character of magnetism and metamagnetism in the effective magnetic field is assumed on the basis of the behavior of magnetization in the metamagnetic transition and analysis of the band structure of the solid solution of cadmium-germanium diarsenide with manganese. 相似文献
7.
Discrete simulation methods are efficient tools to investigate the behaviors of complex fluids such as dry granular materials
or dilute suspensions of hard particles. By contrast, materials made of soft and/or concentrated units (emulsions, foams,
vesicles, dense suspensions) can exhibit both significant elastic particle deflections (Hertz-like response) and strong viscous
forces (squeezed liquid). We point out that the gap between two particles is then not determined solely by the positions of
their centers, but rather exhibits its own dynamics. We provide the first ingredients of a new discrete numerical method,
named Soft Dynamics, to simulate the combined dynamics of particles and contacts. As an illustration, we present the results for the approach
of two particles. We recover the scaling behaviors expected in three limits: the Stokes limit for very large gaps, the Poiseuille-lubricated limit for small gaps and even smaller surface deflections, and the Hertz limit for significant surface deflections. We find that for each gap value, an optimal force achieves the fastest approach
velocity. The principle of larger-scale simulations with this new method is provided. They will consitute a promising tool
for investigating the collective behaviors of many complex materials. 相似文献
8.
H.-F. Li Y. Su Tapan Chatterji A. Nefedov J. Persson P. Meuffels Y. Xiao D. Vaknin Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,74(4):457-461
Soft X-ray resonant scattering studies at the Mn LII, III- and the La MIV, V- edges of single-crystal LaSr2Mn2O7 are
reported. At low temperatures, below TN ≈ 160 K, energy scans with a fixed momentum transfer at the A-type antiferromagnetic (0 0
1) reflection around the Mn LII, III-edges with incident linear σ and π polarizations show strong resonant enhancements. The
splitting of the energy spectra around the Mn LII, III-edges may indicate the presence of a mixed valence state, e.g., Mn3+/Mn4+.
The relative intensities of the resonance and the clear shoulder-feature as well as the strong incident σ and π polarization
dependences
strongly indicate its complex electronic origin. Unexpected enhancement of the charge Bragg (0 0 2) reflection at the La MIV, V-edges with
σ polarization has been observed up to 300 K, with an anomaly appearing around the orbital-ordering transition temperature,
TOO ≈
220 K, suggesting a strong coupling (competition) between them. 相似文献
9.
N. G. Zamkova S. N. Sofronova V. I. Zinenko 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(2):224-227
Ferroelectric phase transitions and thermodynamic properties of disordered PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3 solid solutions have been investigated by the Monte Carlo method. The parameters of the effective Hamiltonian were calculated within the generalized Gordon-Kim model. The obtained values of the phase-transition temperatures and spontaneous polarization are in satisfactory agreement with the experimental data. 相似文献
10.
V. I. Zinenko N. G. Zamkova E. G. Maksimov S. N. Sofronova 《Journal of Experimental and Theoretical Physics》2007,105(3):617-625
The dynamic Born charges and the frequency spectra of lattice oscillations in the crystals of ordered and disordered PbSc1/2Ta1/2O3 (PST) and PbSc1/2Nb1/2O3 (PSN) solid solutions have been calculated within the framework of the generalized Gordon-Kim model with allowance for the dipole and quadrupole polarizabilities. The phonon spectra of both compounds contain ferroelectric soft modes. The influence of various interactions on the magnitude of dynamic charges and ferroelectric instability in PSN and PST solid solutions has been studied and it is shown that both these charges and the ferroelectric instability are determined by the competition between long-range dipole-dipole interactions and short-range dipole-charge interactions, the determining role played by the interaction of Nb (Ta) cations and oxygen anions in the Nb-O (Ta-O) bond direction. 相似文献
11.
High-frequency losses in the strongly anisotropic layered superconductor Bi2Sr2CaCu2O8 are measured at 600 MHz under a magnetic field rocking about the ab plane. Anomalies in losses and hysteretic phenomena are found while performing periodic rocking, i.e., cycling the magnetic field component normal to the sample surface. Based on these observations, conclusions are drawn about the nature of magnetic-flux penetration into the superconductor. It is found that, in the range between 60 K and T c , the dynamics of magnetic-flux vortex lines normal to the ab plane in the presence of a constant magnetic field applied parallel to this plane is governed by the critical penetration field H c ⊥* and the surface barrier in the presence of thermally activated vortex motion (giant flux creep). The dependences of H c1 ⊥* and the characteristic field of the surface barrier on the magnitude of the parallel magnetic field are measured. 相似文献
12.
Hierarchical Na2FeP2O7 spheres with nanoparticles were successfully fabricated by a facile spray drying method. A relatively low drying temperature was introduced in order to form a carbon layer on the surface. As a cathode material for sodium-ion batteries, it delivered a reversible capacity of 84.4 mAh g?1 at 0.1 C and showed excellent cycling and rate performance (64.7 mAh g?1 at 5 C). Furthermore, a full sodium battery was fabricated using SP-Na2FeP2O7 as the cathode and hard carbon as the anode, suffering almost no capacity loss after 400 cycles at 1 C. Due to its superior electrochemical property and the low materials cost, Na2FeP2O7 is becoming a promising cathode material for large-scale energy storage systems. 相似文献
13.
The temperature dependences of the velocity of longitudinal sound and internal friction in the ferromagnetic La0.5Pr0.2Ca0.3MnO3 single crystal with magnetic first-order phase transition were studied. It was found that the sound velocity decreases by ≈20% in transition from the ferromagnetic to paramagnetic state. In the paramagnetic region, the extended temperature hysteresis of the sound velocity and the internal friction was observed. It was shown that La0.5Pr0.2Ca0.3MnO3 has two paramagnetic phases with different sound velocities. 相似文献
14.
M. O. Eremin 《Physical Mesomechanics》2016,19(4):452-458
The regular grid generation method was generalized for a 3D region based on the solid mechanics equations that describe deformation of a finite volume. Test calculations of fracture of ceramic composites with inclusions are represented which are based on the developed model of quasi-brittle media with regard to damage accumulation. 相似文献
15.
16.
Two sets of samples of SnO2/In2O3/TiO2 system have been fabricated with different concentrations of component materials. In the first set TiO2 with rutile structure was used, while in the second set it has the structure of anatase. Thin films (up to 50 nm) of obtained
mixtures were deposited. Their sensitivity and selectivity with respect to methane (CH4) were studied. Nanostructure on the
basis of 70%SnO2 — 10%In2O3 — 20%TiO2(anatase) exhibits sufficient sensitivity to methane. 相似文献
17.
18.
A. I. Burkhanov Yu. V. Kochergin K. Bormanis A. Kalvane 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1264-1266
The dielectric nonlinearity in BaBi2Nb2O9 and SrBi2Ta2O9 layered ceramics was studied by measuring their polarization loops and reverse dependences of permittivity. It was shown
that the features of the dielectric response of BaBi2Nb2O9 and SrBi2Ta2O9 in strong fields can be explained by glass-like properties and the contribution of the domain structure of the ferroelectric
material to repolarization processes, respectively. 相似文献
19.
H. Cherkani-Hassani D. S. Belic J. J. Jureta J. Lecointre P. Defrance 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,58(1):85-94
Absolute cross-sections for electron-impact dissociative ionization of C2
H2+ and C2 D2+ to CH+, C+, C2+ , H+, CH2+
and C2D+ fragments are determined for electron energies ranging
from the corresponding threshold to 2.5 keV. Results obtained in a crossed
beams experiment are analyzed to estimate the contribution of dissociative
ionization to each fragment formation. The dissociative ionization cross
sections are seen to decrease for more than an order of magnitude, from
CH+ (5.37±0.10) × 10-17 cm2 over C+ (4.19±
0.16) × 10-17 cm2, C2D+ (3.94±0.38) ×
10-17 cm2, C2+ (3.82±0.15) × 10-17 cm2
and H+ (3.37±0.21) × 10-17 cm2 to CH2+
(2.66±0.14) × 10-18 cm2. Kinetic energy release
distributions of fragment ions are also determined from the analysis of the
product velocity distribution. Cross section values, threshold energies and
kinetic energies are compared with the data available from the literature.
Conforming to the scheme used in the study of the dissociative excitation of
C2H2+
( C2 D2+ )\left( {\rm C}_2 {\rm D}_2^+ \right), the cross-sections are presented in
a format suitable for their implementation in plasma simulation codes. 相似文献
20.
A. D. Gorlov 《Physics of the Solid State》2004,46(11):2030-2034
This paper reports on the results of ligand electron-nuclear double resonance (ENDOR) investigations of T1 trigonal 157Gd3+ centers in the CaF2 compound. It is experimentally found that the nearest environment of an impurity center contains only one 19F ion. Anions in the other coordination shells are identical to those in the pure CaF2 crystal. However, 19F ions in these shells are displaced from their ideal positions in the lattice. The parameters of the ligand hyperfine interaction (LHFI) for 19F nuclei and their coordinates and displacements with respect to the positions in the lattice of the pure CaF2 crystal are determined. It is demonstrated that the unusual isotropic LHFI constant A s >0 for Gd3+ ions in the lattice with a mixed oxygen-fluorine nearest environment can be associated with the strong polarization of impurity centers in accordance with the empirical model proposed in [1], provided the structural model of the nearest environment of impurities in the T1 centers [2] is correct. This structural model is confirmed by the analysis of the isotropic hyperfine constant A(s) for 157Gd3+ centers. 相似文献