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The intermetallic compound YMnAl, crystallizing in the cubic C-15 (MgCu 2 -type) structure, was prepared using arc-melting and annealing. Rietveld refinement of the XRD pattern yields a lattice parameter of a = 7.816(1) Å. The system exhibits antiferromagnetic order with a transition temperature of approximately 38 K, along with indications of a spin-glass–like phase. The effective magnetic moment, estimated from Curie–Weiss fitting of the susceptibility versus temperature curve, is 6.06 μ B /f.u. and the Curie–Weiss temperature of −79 K confirming the antiferromagnetic nature. Isothermal magnetization measurements below and above the Néel temperature show no saturation, with a maximum magnetization of 0.09 μ B /f.u observed at an applied field of 9 T. The temperature dependence of resistivity exhibits a negative temperature coefficient, characteristic of dirty metals. Hall effect measurements indicate the absence of an anomalous Hall contribution. The Hall coefficient RH, carrier concentration n, and mobility μ estimated from R XY (H) are -1.05×10 -8 m 3 /C, 5.92×10 26 m -3 and 1.05×10 -3 m 2 /V.s, respectively. Our first-principles calculations indicate that YMnAl in the orthorhombic (Imma) structure has the lowest energy; however, the substitutional disorder occurring during experimental synthesis may favor the formation of the cubic Laves phase.
Ionization fraction as independent variable in plasma transport correlation, noting role in pressure effect increase
A self-consistent set of equilibrium air values were computed for enthalpy, total specific heat at constant pressure, compressibility factor, viscosity, total thermal conductivity, and total Prandtl number from 500 to 30,000 K over a range of 10(exp -4) atm to 10(exp 2) atm. The mixture values are calculated from the transport and thermodynamic properties of the individual species provided in a recent study by the authors. The concentrations of the individual species, required in the mixture relations, are obtained from a free energy minimization calculation procedure. Present calculations are based on an 11-species air model. For pressures less than 10(exp -2) atm and temperatures of about 15,000 K and greater, the concentrations of N(++) and O(++) become important, and consequently, they are included in the calculations determining the various properties. The computed properties are curve fitted as a function of temperature at a constant value of pressure. These curve fits reproduce the computed values within 5 percent for the entire temperature range considered here at specific pressures and provide an efficient means for computing the flowfield properties of equilibrium air, provided the elemental composition remains constant at 0.24 for oxygen and 0.76 for nitrogen by mass.
Radiation damage and transport damage in solar cells
The paper describes the processing and electrical transport measurements for achieving reproducible high-Tc and high-Jc sputtered TlCaBaCuO thin films on LaAlO3 substrates, for microelectronic applications. The microwave properties of TlCaBaCuO thin films were investigated by designing, fabricating, and characterizing microstrip ring resonators with a fundamental resonance frequency of 12 GHz on 10-mil-thick LaAlO3 substrates. Typical unloaded quality factors for a ring resonator with a superconducting ground plane of 0.3 micron-thickness and a gold ground plane of 1-micron-thickness were above 1500 at 65 K. Typical values of penetration depth at 0 K in the TlCaBaCuO thin films were between 7000 and 8000 A.
First and second order density corrections to transport coefficients of moderately dense gas
Single crystal p-type zinc antimonide in thermoelectric, thermoconductivity and electronic transport measurements
Previous work on the mass transport rate of the GeSe-GeI4 system has been reevaluated using the mass spectrometric results of Buchan and Rosenberger (1987), and considering the presence of GeSe(s) and GeSe2(s) phases in the source material. The present transport rate study confirms the previously derived dominance of the sublimation of GeSe at lower pressures of GeI4, and of chemical vapor transport at higher pressures of GeI4. It is noted that experimentally observed flux anomalies are model-independent.
The comparative investigation of transport phenomena in Y(1-x)Ca(x)Ba2Cu3O(y) (0 is less than x is less than 0.25; 6.96 is greater than y is greater than 6.87 and 6.73 is less than x is less than 6.53); Y(1-x)Ca(x)Ba(1.5)La(0.5)Cu3O(y) (0 is less than x is less than 0.5; 7.12 is greater than y is greater than 6.96) and YBa(2-x)La(x)Cu3O(y) (0 is less than x is less than 0.5; 6.95 is less than y is less than 7.21) systems have been carried out. The temperature dependencies of resistivity and thermopower have been measured. It was found that the S(T) dependencies take some additional features with Ca content increase. The results obtained have been analyzed on the basis of the phenomenological theory of electron transport in the case of the narrow conductive band. The main parameters of the band spectrum (the band filling with electrons degree and the total effective band width) have been determined. The dependencies of these from contents of substituting elements are discussed. Analyzing the results obtained simultaneously with the tendencies in oxygen content and critical temperature change we have confirmed the conclusion that the oxygen sublattice disordering has a determinant effect on band structure parameters and superconductive properties of YBa2Cu3O(y). The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.
Device-quality tensile-strained Ge (ε-Ge) grown on a large bandgap semiconductor with superior electrical and optical carrier confinement is essential for group-IV-based optoelectronics. Properties of ε-Ge active layers synthesized on In 0.24 Ga 0.76 As buffers with two different surface terminations─arsenic-rich and indium-rich─were experimentally demonstrated, highlighting the factors not considered in theoretical calculations. High-resolution X-ray diffraction and Raman spectroscopy analyses of these ε-Ge/In 0.24 Ga 0.76 As heterostructures confirmed the fully strained (1.6%) and partially relaxed (0.82%) nature of the ε-Ge bonded with arsenic-terminated (Ge As-terminated ) and indium-terminated (Ge In-terminated ) In 0.24 Ga 0.76 As stressors, respectively. High-resolution cross-sectional transmission electron microscopy showed a coherent, sharp, and fully strained ε-Ge/In 0.24 Ga 0.76 As heterointerface in the Ge As-terminated heterostructure, whereas microtwin defects were present in the Ge In-terminated heterostructure. These heterostructures were further characterized by evaluating the minority carrier lifetimes, high for Ge As-terminated (525 ns) and low for Ge In-terminated (69 ns), using the photoconductive decay technique. Moreover, band alignment was constructed using X-ray photoelectron spectroscopy, where the Ge As-terminated heterostructure revealed that both holes and electrons were confined within the ε-Ge active layer as a type-I band alignment with ΔE V, As-terminated = 0.22 eV and ΔE C,As-terminated = 0.38 eV. On the other hand, the Ge In-terminated heterostructure exhibited a type-II band alignment with ΔE V,In-terminated = – 0.02 eV and ΔE C,In-terminated = 0.53 eV. Furthermore, the magnetotransport properties revealed high mobility (321 cm 2 /(V s)) with single-electron transport in Ge As-terminated heterostructure and low mobility (3.34 cm 2 /(V s)) with multihole transport in the Ge In-terminated heterostructure. Therefore, preferring the ε-Ge on the arsenic-rich surface of In 0.24 Ga 0.76 As stressor over the indium-rich surface during material synthesis offers device-quality materials with high carrier lifetime and superior carrier confinement, which can provide an opportunity to fabricate efficient group-IV-based optoelectronic devices.
Sulfonated polysulfone is a promising membrane material for separation and energy generation processes that rely on membranes to control the rates of small-molecule (e.g., water and ions) transport. The interactions among water molecules, ions, and the sulfonate groups in these polymers play a key role in controlling these rates of transport, but much remains unknown about these fundamental interactions in sulfonated polymers. In this study, we used dielectric relaxation spectroscopy to characterize water molecule dynamics in sulfonated polysulfone and Nafion. We found that the charged sulfonate groups contribute to a restriction of water molecule dynamics (i.e., a reduction in the characteristic time scale of dipolar motions) in a manner that is governed by the concentration and nature (i.e., conjugate base strength) of the sulfonate group. Additionally, we develop strategies to use these data to aid in modeling ion transport in sulfonated polysulfone. These results may be useful to guide engineering strategies for polymeric membranes.
Numerical evaluation of first and second order density corrections for transport coefficients of gas of Lennard-Jones molecules
A general computer code was developed to allow calculation of atom-atom and ion-atom transport collision integrals from accurate potential energy curves described by a set of discrete data points for a broad range of scattering conditions. This code is based upon semiclassical approximations that properly account for quantum mechanical behavior such as tunneling effects near a barrier maximum, resonance charge exchange, and nuclear symmetry effects. Transport collision integrals were determined for N-N, O-O, N(+)-N, and O(+)-O interactions from complete sets of accurate potential functions derived from combined experimental and ab initio structure calculations. For the O-O case, this includes results for excited states. The calculated values of the N(+)-N and O(+)-O resonance charge exchange cross section Q(ex) agree well with measurements from beam experiment that are available at high energies where the diffusion cross section Q(d) satisfies Q(d) approximately equal to 2Q(ex).
Estimates of potential energy curves for interaction of ground-state alkali metal atoms used to calculate transport collision integrals
Here, we report a systematic investigation of the physical properties and Fermi-surface topology of layered single-crystal SrCu 4 As 2 using electrical transport, magnetotransport, and quantum-oscillation experiments plus band-structure calculations. The temperature-dependent electrical resistivity reveals a hysteretic phase transition at 𝑇 𝑃 =59 K, most likely associated with a structural change. Hall resistivity data suggest a marked change in the average hole density resulting from the latter phase transition near 𝑇 𝑃 . A large, linear, and nonsaturating magnetoresistance is observed at low temperatures in SrCu 4 As 2 , likely attributable to the multipocket Fermi surface. Quantum-oscillation data measured in magnetic fields of up to 60 T show several oscillation frequencies exhibiting low effective masses, indicating the presence of Dirac-like band dispersion in SrCu 4 As 2 , as suggested by the band structure calculations.
One of the most compelling reasons for performing data assimilation in the middle atmosphere is to obtain global, balanced datasets for studies of trace gas transport and chemistry. This is a major motivation behind the Goddard Earth observation System-Data Assimilation System (GEOS-DAS). Previous studies have shown that while this and other data assimilation systems can generally obtain good estimates of the extratropical rotational velocity field, the divergent part of the dynamical field is deficient; this impacts the "residual circulation" and leads to spurious trace gas transport on seasonal and interannual timescales. These problems are impacted by the quality and the method of use of the observational data and by deficiencies in the atmospheric general circulation model. Whichever the cause at any place and time, the "solution" is to introduce non-physical forcing terms into the system (the so-called incremental analysis updates); these can directly (thermal) or indirectly (mechanical) affect the residual circulation. This paper will illustrate how the divergent circulation is affected by deficiencies in both observations and models. Theoretical considerations will be illustrated with examples from the GEOS-DAS and from simplified numerical experiments. These are designed to isolate known problems, such as the inability of models to sustain a quasi-biennial oscillation and sparse observational constraints on tropical dynamics, or radiative inconsistencies in the presence of volcanic aerosols.
One of the most compelling reasons for performing data assimilation in the middle atmosphere is to obtain global, balanced datasets for studies of trace gas transport and chemistry. This is a major motivation behind the Goddard Earth observation System-Data Assimilation System (GEOS-DAS). Previous studies have shown that while this and other data assimilation systems can generally obtain good estimates of the extratropical rotational velocity field, the divergent part of the dynamical field is deficient; this impacts the "residual circulation" and leads to spurious trace gas transport on seasonal and interannual timescales. These problems are impacted by the quality and the method of use of the observational data and by deficiencies in the atmospheric general circulation model. Whichever the cause at any place and time, the "solution" is to introduce non-physical forcing terms into the system (the so-called incremental analysis updates); these can directly (thermal) or indirectly (mechanical) affect the residual circulation. This paper will illustrate how the divergent circulation is affected by deficiencies in both observations and models. Theoretical considerations will be illustrated with examples from the GEOS-DAS and from simplified numerical experiments. These are designed to isolate known problems, such as the inability of models to sustain a quasi-biennial oscillation and sparse observational constraints on tropical dynamics, or radiative inconsistencies in the presence of volcanic aerosols.