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First principle calculations have been employed to investigate the effects of Y concentration, pressure and temperature on various properties of Gd1?xYxAuPb (x=0,0.25,0.5,0.75,1) alloys using density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) is used to perform the calculated results of this paper. Phase stability of Gd1?xYxAuPb alloys is studied using the total energy versus unit cell volume calculations. The equilibrium lattice parameters of these alloys are in good agreement with the available experimental results. The mechanical stability of Gd1?xYxAuPb alloys is proved using elastic constants calculations. Also, the influence of Y concentration on elastic properties of Gd1?xYxAuPb alloys such as Young's modulus, shear modulus, Poisson's ratio and anisotropy factor are investigated and analyzed. By considering both Pugh's ratio and Poisson's ratio, the ductility and brittleness of these alloys are studied. In addition, the total density of states and orbital's hybridizations of different atoms are investigated and discussed. Moreover, the effect of pressure and temperature on some important thermodynamic properties is investigated.  相似文献   

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An investigation into the superconducting order parameter thermodynamic fluctuations and their manifestations on paraconductivity in cuprate superconductors is done using a renormalized Gaussian approach based on the Ginzburg–Landau theory. The temperature dependence of paraconductivity is affected by repulsive interactions between Cooper pairs and does not follow the universal power laws predicted by the conventional Aslamazov–Larkin theory. In addition to the well known Lawrence–Doniach crossover from three to two dimensions, we also highlight the crossover from one-dimensional to two-dimensional behavior and the crossover from weak two-dimensional to strong two-dimensional critical behavior in the vicinity of the critical temperature. These dimensional crossovers result from the resistance between Cooper pairs due to critical and thermal fluctuations which cause a transition from a metastable state to one with a smaller current. Two illustrative examples (the cases of YBa2Cu3O6.9 and Bi2Sr2CaCu30x compounds) are provided in support of the analysis, so as to demonstrate the usefulness of the approach.  相似文献   

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Nanoparticles of CdxMg0.12?xZn0.88O (0x0.02) were synthesized by a simple sol gel route with the combination of chelating agents. Effect of cadmium on the phase, structural, morphological and optical properties of the synthesized nanoparticles has been studied and reported by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR) and UV–Vis diffuse reflectance spectroscopy (UV–vis DRS). The crystal size, lattice parameters, unit cell volume, X-ray density, inter-planar distances and bond length were obtained and analyzed from the XRD data. The X-ray analysis reveals the formation of a single phase with a hexagonal wurtzite structure, where an increase of the cell volume was achieved as the Cd content was increased as well. Synthesized nanoparticle were nearly spherical at nano-size regime and are loosely agglomerated as observed from the SEM analysis. EDX spectra of the composition confirmed the appropriate stoichiometric ratio. A fundamental absorption peak centered at 375 nm was observed from the UV–visible absorption spectra which shifted towards a higher wavelength correlating the narrowing of the energy band gap due to increase in Cd content. The structural adjustment from the IR spectra confirmed the stretching vibration of Zn–O in the CdxMg0.12?xZn0.88O lattice with Cd content.  相似文献   

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In this paper, we discuss a method based on wavelet analysis for the study of the q-index of the Gaussian distribution. We derive q-index from the scale index, iscale, using the expression; q1+2iscale where iscale is a wavelet based tool for measuring the degree of aperiodicity of a dynamical system in the range of 0iscale1. We show that this expression gives consistent results with the numerical approach of q-Gaussian distribution which determines the degree of non-extensivity of a dynamical system in the range of 1<q<3. We also suggest a new entropy calculation method based on the normalized inner scalogram for studying the chaotic characteristics of nonlinear dynamical systems.  相似文献   

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《Physics letters. A》2019,383(17):2114-2119
We provide a detailed analysis of a topological structure of a fermion spectrum in the Hofstadter model with different hopping integrals along the x,y,z-links (tx=t,ty=tz=1), defined on a honeycomb lattice. We have shown that the chiral gapless edge modes are described in the framework of the generalized Kitaev chain formalism, which makes it possible to calculate the Hall conductance of subbands for different filling and an arbitrary magnetic flux ϕ. At half-filling the gap in the center of the fermion spectrum opens for t>tc=2ϕ, a quantum phase transition in the 2D-topological insulator state is realized at tc. The phase state is characterized by zero energy Majorana states localized at the boundaries. Taking into account the on-site Coulomb repulsion U (where U<<1), the criterion for the stability of a topological insulator state is calculated at t<<1, tU. Thus, in the case of U>4Δ, the topological insulator state, which is determined by chiral gapless edge modes in the gap Δ, is destroyed.  相似文献   

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《Physics letters. A》2019,383(18):2229-2234
In this work, the exchange bias behavior and magnetocaloric effect have been studied in Mn7Sn4 alloy. The X-ray powder diffraction pattern recorded at room temperature indicates that the sample crystallizes in a single phase with Ni2In-type hexagonal structure (space group P63/mmc). The maximum magnetic entropy change value across paramagnetic/ferrimagnetic transition is about 3.3 J kg−1 K−1 under the magnetic field change of μ0ΔH=0-5T. With further cooling, the reentrant spin-glass-like state is obtained below 150 K, for which the exchange bias effect has been observed. The exchange bias field is ∼7.8 mT and ∼6.7 mT at T=10K when the cooling field is μ0HCF=0.1T and 0.5 T, respectively. The magnetic behavior and the origin of exchange bias in Mn7Sn4 are discussed.  相似文献   

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