Showing papers by "Argonne National Laboratory published in 1980"
TL;DR: In this paper, it was shown that different pair potentials lead to different crystal structures, with the use of a Lagrangian which allows for the variation of the shape and size of the periodically repeating molecular-dynamics cell.
Abstract: With use of a Lagrangian which allows for the variation of the shape and size of the periodically repeating molecular-dynamics cell, it is shown that different pair potentials lead to different crystal structures.
2,630 citations
01 Jan 1980
455 citations
437 citations
TL;DR: In this paper, a new class of layered materials has been prepared by alternate deposition of two dissimilar metals, and strong experimental evidence is shown that coherent structures with layer thicknesses approaching interatomic spacing can be prepared in this fashion.
Abstract: A new class of layered materials has been prepared by alternate deposition of two dissimilar metals. Strong experimental evidence is shown that coherent structures with layer thicknesses approaching interatomic spacing can be prepared in this fashion. The experimental x-ray measurements are found to be in good qualitative and quantitative agreement with model calculations.
427 citations
TL;DR: In this paper, the authors describe a fully relativistic augmented plane wave (APW) method where the basis functions are pure spin functions in the large component, which allows spin-mixing interactions to be separated and treated more efficiently than in the standard APW method.
Abstract: The authors describe a fully relativistic augmented-plane-wave (APW) method where the basis functions are pure spin functions in the large component. This feature allows spin-mixing interactions to be separated and treated more efficiently than in the standard relativistic APW method. These basis functions are constructed by solving an approximate relativistic radial equation. In addition, the energy derivative is used in the construction of the basis functions so that one obtains adequate variational freedom solving a linear secular equation. Both the utility and the limitations of the technique are discussed.
409 citations
TL;DR: An iterative, self-consistent procedure for the Kramers-Kronig analysis of data from reflectance, ellipsometric, transmission, and electron-energy-loss measurements is presented in this paper.
Abstract: An iterative, self-consistent procedure for the Kramers-Kronig analysis of data from reflectance, ellipsometric, transmission, and electron-energy-loss measurements is presented. This procedure has been developed for practical dispersion analysis since experimentally no single optical function can be readily measured over the entire range of frequencies as required by the Kramers-Kronig relations. The present technique is applied to metallic aluminum as an example. The results are then examined for internal consistency and for systematic errors by various optical sum rules. The present procedure affords a systematic means of preparing a self-consistent set of optical functions provided some optical or energy-loss data are available in all important spectral regions. The analysis of aluminum discloses that currently available data exhibit an excess oscillator strength, apparently in the vicinity of the L edge. A possible explanation is a systematic experimental error in the absorption-coefficient measurements resulting from surface layers: possibly oxides: present in thin-film transmission samples. A revised set of optical functions has been prepared by an ad hoc reduction of the reported absorption coefficient above the L edge by 14%. These revised data lead to a total oscillator strength consistent with the known electron density and are in agreement with dc-conductivity and stopping-power measurementsmore » as well as with absorption coefficients inferred from the cross sections of neighboring elements in the periodic table. The optical functions resulting from this study show evidence for both the redistribution of oscillator strength between energy levels and the effects on real transitions of the shielding of conduction electrons by virtual processes in the core states.« less
325 citations
TL;DR: In this article, the activation enthalpies for diffusion of the major constituents in any one alloy are quite close to each other, and no correlation is found between swelling under irradiation and the diffusion behavior of major constituents.
Abstract: The simultaneous lattice diffusion of 59Fe, 51Cr and 57Ni tracers has been measured in the alloys Fe-15Cr-20Ni, Fe-15Cr-45Ni, Fe-22Cr-45Ni and Fe-15Cr-20Ni-1.4Si between 960 and 1400 degrees C. In all four alloys at all temperatures, DCr>DFe>DNi, with DCr/DNi approximately=2.5 and DFe/DNi approximately=1.8. The activation enthalpies for diffusion of the major constituents in any one alloy are quite close to each other. No correlation is found between swelling under irradiation and the diffusion behaviour of the major constituents. The results are discussed on the basis of the random-alloy model. Grain-boundary diffusion is found in these alloys at surprisingly high temperatures.
246 citations
TL;DR: Investigation of the breath 13CO2 response to individual 13C-labeled dietary constituents demonstrated that amino acids produced the earliest 13 CO2 response followed in order by medium chain triglyceride, carbohydrates, and long chain triglycerides.
219 citations
TL;DR: In this paper, the identity of the pentaiodide (I(5-1)) anion has been determined by resonance Raman and I -129 Mossbauer spectroscopy.
Abstract: : The structure of the blue-black iodine complex of amylose (the linear, helical component of starch) prepared either from iodine and iodide in aqueous solution or from crystalline amylose and iodine vapor, has been studied by resonance Raman and iodine -129 Mossbauer spectroscopy. In both cases it is concluded that the identity of the major chromophore is essentially the same: the pentaiodide (I(5-1)) anion. For the material prepared from iodine vapor, the iodide required for (I(5-1)) formation is produced by hydrolysis or alcoholysis of iodine. The other product of this reaction, a hypoiodite, has been assigned in the iodine Mossbauer spectrum. (Author)
165 citations
TL;DR: In this paper, the wave deformation limit and the most dangerous wave concept were introduced in the stability analysis of a slug flow in a horizontal duct, and a potential flow analysis was carried out by considering waves of finite amplitude.
Abstract: A criterion for the onset of a slug flow in a horizontal duct is derived theoretically. A potential flow analysis is carried out by considering waves of finite amplitude. The stability criterion is obtained by introducing the wave deformation limit and the “most dangerous wave” concept in the stability analysis. The present theoretical criterion for slug formation shows very good agreement with a large number of experimental data and with some empirical correlations.
158 citations
TL;DR: Ohnishi et al. as mentioned in this paper showed that the same slab geometry with a 6% surface layer contraction does not bring any significant difference in the surface electronic structure; in particular, spectral properties and work function are insensitive to this lattice parameter difference.
Abstract: The low-temperature value of the tungsten bulk lattice parameter is 5.973 a.u. [N. E. Christensen and B. Feuerbacher, Phys. Rev. B 10, 2349 (1974)]. In our calculation, we used by mistake the value of 5.793 a.u. Our conclusions, however, are insensitive to this 3% difference, as confirmed by the following: (i) The same slab geometry, with a 6% surface layer contraction does not bring any significant difference in the surface electronic structure [M. Posternak, H. Krakauer, and A. J. Freeman, Phys. Rev. B 25, 755 (1982)](ii) Subsequent calculations by Ohnishi et al. [Phys. Rev. B 29, 5267 (1984)] and Mattheiss and Hamann [Phys. Rev. B 29, 5372 (1984)] give results in good agreement with ours; in particular, spectral properties and work function are insensitive to this lattice parameter difference.
TL;DR: In this paper, the authors have shown that the equilibrium vacancy concentration at the melting point is Cv(Tm=3695 K) ≃ 1 × 10−4 using this value, the vacancy resistivity and formation entropy, pIV=6·3 × 10 −4 Ω cm and SIV F=2·3k respectively, were deduced.
Abstract: Resistivity and transmission-electron-microscopy investigations have been carried out on high-purity quenched tungsten These have yielded values for the monovacancy formation and migration enthalpies of HIV F=3·67±0·2 eV and HIVM=1·78 ± 01 eV respectively, Direct observations of voids formed by vacancy precipitation during quenching and subsequent annealing have led to the conclusion that the equilibrium vacancy concentration at the melting point is Cv(Tm=3695 K) ≃ 1 × 10−4 Using this value, the vacancy resistivity and formation entropy, pIV=6·3 × 10−4 Ω cm and SIV F=2·3k respectively, were deduced The results are discussed in relation to self-diffusion in tungsten and difficulties encountered in earlier work on quenched tungsten
TL;DR: In this paper, the average fluctuation cross sections were computed numerically from a unitary analytic K -matrix with normally distributed pole residue amplitudes and pole spacings having the Wigner distribution.
TL;DR: In this article, an unexpected electron spin echo phase shift was observed for one of the electron spin polarized EPR signals which was detected within 30-40 ns of laser excitation of photosynthetic algae.
TL;DR: In this article, Doubledly charged ion abundances and photoionization mass spectra produced by He(I)α and He(Il)α radiation are reported for molecules from several classes of compound, and are compared to data from previous electron and photon impact investigations.
TL;DR: In this article, the interstitial hole size and H-H interatomic distance were used to predict the stoichiometries and the hydrogen occupied sites in hydrides of the intermetallic compound ZrNi and other isostructural compounds.
Abstract: Criteria of interstitial hole size and H-H interatomic distance were used to predict the stoichiometries and the hydrogen-occupied sites in hydrides of the intermetallic compound ZrNi and other isostructural compounds. With only these simple considerations of geometry it was possible to rationalize most of the experimental observations available for such compounds. A number of neutron diffraction experiments are recommended to test some of the predictions presented.
TL;DR: An experimental investigation of the deleterious effect of microbial slime layers on the hydraulic performance of water conduits is presented in this paper, where the underlying mechanisms that lead to an increase of frictional losses in the conduit are explored and their relative importance is discussed.
Abstract: An experimental investigation of the deleterious effect of microbial slime layers on the hydraulic performance of water conduits is presented. The underlying mechanisms that lead to an increase of frictional losses in the conduit are explored and their relative importance is discussed. It is shown that although the slime layer is viscoelastic and filamentous, its effect on frictional resistance can be adequately represented through an increase in rigid equivalent sand roughness of the conduit wall.
TL;DR: In this paper, the authors present a unified survey of the analysis of uniaxial tensile tensile instabilities and their relation to fracture strain sensitivity, and compare the results of the more recent analyses with Hart's theory, although this author has been either misinterpreted or totally overlooked.
TL;DR: The first ab initio self-consistent spin-polarized energy-band study of a ferromagnetic transition-metal film [Ni(001) was performed by as discussed by the authors.
Abstract: Results are presented of the first ab initio self-consistent spin-polarized energy-band study of a ferromagnetic transition-metal film [Ni(001)] that is thick enough (nine layers) to accurately determine the energy dispersion and spatial character of surface states and their effects on the surface spin polarization, surface magnetic moments, and average exchange splittings. Band structures and surface states, layer density of states, and charge and spin densities are presented and used to discuss a number of experiments. We find no evidence for magnetically "dead layers" on Ni(001) surfaces. The surface-layer magnetic spin moment is reduced by 20% from the center-layer magnetic moment (which has the bulk value) due to a majority-spin $d$-hole surface state at $\overline{M}$ which lies just above the Fermi energy.
TL;DR: The relativistic random phase approximation (RRPA) as discussed by the authors was developed from linearized time-dependent Hartree-Fock theory and applied to determine excitation energies and oscillator strengths along the He, Be, Mg, Zn and Ne isoelectronic sequences.
Abstract: The relativistic random phase approximation RRPA is developed from linearized time-dependent Hartree-Fock theory. Applications of the resulting relativistic many-body equations to determine excitation energies and oscillator strengths along the He, Be, Mg, Zn and Ne isoelectronic sequences are discussed and compared with other recent experimental and theoretical work. The multi-channel RRPA treatment of photoionization is described and applications are given to total cross sections, branching ratios, angular distributions and to autoionizing resonances.
TL;DR: In this article, the problem of vapor/liquid interaction and entrainment in falling film evaporators is analyzed, focusing primarily on horizontal tube falling film evaporation where liquid falls from one tube to the next in either a droplet or column mode.
Abstract: The problem of vapor/liquid interaction and entrainment in falling film evaporators is analyzed. Attention is focused primarily on horizontal tube falling film evaporators where liquid falls from one tube to the next in either a droplet or column mode. A criterion is presented for the onset of column formation, and equations are derived for the deflection of droplets and columns due to vapor crossflow. Based on an experimental study of drop detachment and breakup, a correlation is established for the resulting droplet sizes. For high vapor crossflow velocities, a criterion is presented for the inception of liquid entrainment by a process known as stripping. Based on the foregoing models, conditions are defined under which vapor/liquid interaction and entrainment are important for falling film evaporators.
TL;DR: The Beutler-Fano autoionizing resonances in the rare-gas atoms argon, krypton, and xenon are studied using the relativistic multichannel quantum-defect theory (MQDT).
Abstract: The Beutler-Fano autoionizing resonances in the rare-gas atoms argon, krypton, and xenon are studied using the relativistic multichannel quantum-defect theory (MQDT). Dynamical parameters for the MQDT analyses are obtained from an ab initio relativistic-random-phase-approximation calculation. The position and profile of these resonances are in good agreement with experimental measurements. Angular distribution and spin polarization of photoelectrons in the resonance regions are also studied and are in close agreement with recent measurements.
TL;DR: In this article, all-atom-all-electron self-consistent semirelativistic linear muffin-tin orbital energy-band studies are reported for Ti${\mathrm{Be}} and Zr${Zn} at ambient and high pressures.
Abstract: All-atom---all-electron self-consistent semirelativistic linear muffin-tin orbital energy-band studies are reported for Ti${\mathrm{Be}}_{2}$, Zr${\mathrm{Zn}}_{2}$ (at ambient and high pressures), the high-${T}_{c}$ superconductor Zr${\mathrm{V}}_{2}$, and the ultralow-${T}_{c}$ superconductor Y${\mathrm{Al}}_{2}$. Total and partial (by atom type and $l$ values) density of states, Stoner-like parameters, electron-phonon coupling parameter $\ensuremath{\lambda}$ and superconducting transition temperatures ${T}_{c}$ (determined within the rigid muffin-tin approximation and McMillan's strong coupling theory with and without paramagnon contributions), and their behavior under applied pressure are used to discuss the origin of their observed magnetism and/or superconductivity. From an analysis of the results, we suggest possible high-${T}_{c}$ superconductivity at high pressure for Zr${\mathrm{Zn}}_{2}$, and its unlikely occurrence for Ti${\mathrm{Be}}_{2}$ unless dominant soft phonon modes exist.
TL;DR: In this paper, the systematics of the electronic structure of perovskite oxides, where the $B$ element scans the $3d$ transition-metal series from Ti to Co, are examined.
Abstract: The systematics of the electronic structure of $\mathrm{La}B{\mathrm{O}}_{3}$ perovskite oxides, where the $B$ element scans the $3d$ transition-metal series from Ti to Co, are examined. X-ray photoelectron spectra of valence bands and shallow core states are presented and compared with theoretical molecular cluster and free-ion multiplet models. Self-consistent ionic configurations are obtained from the embedded cluster calculations, which differ from the assumptions of crystal-field theory due to metal-oxygen covalency. The prospect for more rigorous many-electron models is discussed.
TL;DR: In this paper, the electronic structures of lanthanum chromites, pure and doped with magnesium and strontium, have been studied in comparison with Cr2O3 and LaCrO3 using X-ray photo-electron spectroscopy.
TL;DR: In this paper, LaNi5 was compacted to form solid porous metallic-matrix hydrides (PMHs), and the PMHs were cycled for preliminary testing and the thermal conductivity was found to be 32.5 W m−1 K−1.
Abstract: Hydrides of LaNi5 were compacted to form solid porous metallic-matrix hydrides (PMHs). Pellets were obtained and were cycled for preliminary testing. The metal matrix was formed from aluminum, copper, nickel etc.; only PMHs using aluminum were tested. The method of preparation yielded pellets that did not disintegrate after repeated cycling. The pellets rapidly absorbed hydrogen from the first cycle, eliminating the need for activation. The kinetics were very fast and the hydrogen capacity was high. Preliminary metallographical analyses showed the microstructure actually obtained. The thermal conductivity was found to be 32.5 W m−1 K−1.
TL;DR: In this paper, the authors outline a view of the mechanism by which cell walls form during the course of strain hardening and dynamic recovery, and explain inconsistencies between x-ray and TEM observations of misorientations, and contribute to a theory of nucleation for recrystallization.
TL;DR: Gibb's isotherm curves were run for a series of dialkyl phosphoric, phosphonic, and phosphinic acids, most in dodecane against 1 M HNO3 at 25°C as discussed by the authors.
TL;DR: In this paper, the experimental results from the polarized-beam program at the Argonne ZGS are reviewed and the main emphasis is placed on the elastic-scattering and total cross-section measurements.