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1 Dec 1981

Volume 52, Issue 12, pp. 7027-7460

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High‐current D− production by charge exchange in sodium

E. B. Hooper, P. Poulsen, and P. A. Pincosy

J. Appl. Phys. 52, 7027 (1981); http://dx.doi.org/10.1063/1.328697 (12 pages) | Cited 3 times

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A beam of D− ions has been produced at 7–13 keV, with currents up to 2.2 A, using charge exchange in sodium vapor. The beam profile is bi‐Gaussian with angular divergence 0.7°×2.8° and peak current density 15 mA/cm2. The characteristics of the beam are in excellent agreement with predictions based on atomic cross sections. The sodium vapor target is formed by a jet directed across the beam. The sodium density drops rapidly in the beamline downstream from the charge exchange region, decreasing three orders of magnitude in 15 cm. Measurement and analysis of the plasma accompanying the beam demonstrate that plasma densities nearly equal to the beam density are obtained 1 m from the charge exchange medium. The plasma produced in the sodium is thus well confined to the charge exchange region and does not propagate along the beam.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
34.70.+e Charge transfer
52.30.-q Plasma dynamics and flow
29.27.Eg Beam handling; beam transport

Measurements and calculations of the anomalous energy broadening of a 300‐eV electron beam

J. J. McClelland, J. M. Ratliff, and M. Fink

J. Appl. Phys. 52, 7039 (1981); http://dx.doi.org/10.1063/1.328698 (5 pages) | Cited 5 times

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Measurements and calculations of the energy full width at half maximum (FWHM) of a 300‐eV electron beam are presented as a function of current. The measurements utilize a low‐energy telefocus electron gun and a 127° cylindrical energy analyzer. The calculations combine theories of Knauer and Zimmermann with beam envelope determinations obtained from a combination of electron ray tracing and measurements on the beam. The energy width is numerically integrated along the beam envelope, and the FWHM is calculated. The calculations agree in magnitude with the measurements, but there is a discrepancy in the current dependence.
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41.75.Fr Electron and positron beams
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
84.47.+w Vacuum tubes

A helical transversely excited copper bromide laser

K.‐H. Krahn

J. Appl. Phys. 52, 7044 (1981); http://dx.doi.org/10.1063/1.328699 (3 pages)

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The construction and successful operation of a helical transversely excited copper bromide laser is reported. Satisfactory laser performance has been obtained over a wide range of discharge parameters. As a consequence of the helical electrode geometry, the copper laser‐beam cross section is circular symmetric and exhibits a radial energy profile that is near to Gaussian.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems

Relative influence of hydrogen/deuterium donors and driving circuit parameters on the performance of a uv preionized pulsed HF/DF laser

R. Marchetti, E. Penco, and G. Salvetti

J. Appl. Phys. 52, 7047 (1981); http://dx.doi.org/10.1063/1.328700 (5 pages) | Cited 1 time

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The influence of the preionizer and initiating discharge circuit parameters on the performance of a UV preionized pulsed HF/DF chemical laser with relatively low active volume (about 20 cm3) has been investigated. The laser has been operated with gas mixtures of SF6 and H2, C2H6, and D2 at pressures ?90 Torr, giving laser output energies up to ∼70 mJ with a maximum efficiency of about 2.2%. We observed that the insertion of a peaking capacitor bank across the main discharge gap strongly affected the laser output characteristics. The laser output energy was seen to vary with the capacitance of the peaking capacitor bank, whose influence is a function of the SF6 partner in the laser mixture, the gas pressure, and the input energy density into the discharge.
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42.55.Ks Chemical lasers
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Theory of lossless suppression of filamentation in high‐power laser beams

F. S. Felber and D. P. Chernin

J. Appl. Phys. 52, 7052 (1981); http://dx.doi.org/10.1063/1.328701 (9 pages) | Cited 4 times

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This paper supports an earlier suggestion that saturation of the optical nonlinearity of a medium by a plane wave will suppress filamentation of the wave. A variational approach and exact solutions of the slowly‐varying‐envelope approximation of the linearized wave equation describe the growth of localized filaments on plane waves. The solutions show that a wave will be stable against filamentation if the wave is weak or if it is intense enough to saturate the nonlinearity of the medium. Experiments are proposed to demonstrate suppression of filamentation of CO2 laser beams exceeding 1010 W and Nd laser beams exceeding 1012 W in fully ionized hydrogen plasmas. The beams saturate the nonlinearity of the plasma by ponderomotive forces; absorption is negligible in the rarefied channel produced by the laser. Applications may include lossless filters that remove intensity hot spots from beams or convert mulitmode beams to nearly single mode.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
42.79.Ci Filters, zone plates, and polarizers
52.35.Mw Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.)

Low‐loss polystyrene core‐optical fibers

Toshikuni Kaino, Michiya Fujiki, and Shigeo Nara

J. Appl. Phys. 52, 7061 (1981); http://dx.doi.org/10.1063/1.328702 (3 pages) | Cited 20 times

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Low‐loss plastic optical fibers (POF) have been prepared with the attenuation loss of 114 dB/km at the wavelength of 670 nm employing polystylene core and ethylene‐vinylacetate copolymer cladding. The POF can allow the use for short‐distance optical signal transmission. The theoretical loss limit of polystylene core POF is calculated to be 70 dB/km at 670 nm.
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42.79.Gn Optical waveguides and couplers
42.25.Lc Birefringence
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Ion response to plasma excitation frequency

R. H. Bruce

J. Appl. Phys. 52, 7064 (1981); http://dx.doi.org/10.1063/1.328703 (3 pages) | Cited 60 times

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The time dependence of the potential distribution in a parallel plate discharge is discussed in terms of a model which indicates the plasma potential oscillates with the applied voltage only over the positive part of the cycle. Measurements of this oscillation have been made, and the response of the ions to the oscillating field has been studied as a function of excitation frequency.
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52.35.Hr Electromagnetic waves (e.g., electron-cyclotron, Whistler, Bernstein, upper hybrid, lower hybrid)

Mixed slow‐wave operation of a wide‐band dielectric gyrotron

Joon Y. Choe, Han S. Uhm, and Saeyoung Ahn

J. Appl. Phys. 52, 7067 (1981); http://dx.doi.org/10.1063/1.328422 (8 pages) | Cited 12 times

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The bandwidth broadening effect of mixing two slow‐wave modes in a dielectric loaded gyrotron is investigated for a small axial momentum spread. The usual intermediate wavelength mode (IWM) integrates with the short wavelength mode (SWM) by reducing the electron beam radius, and creates a mixed slow wave. The resulting bandwidth for the mixed mode gyrotron becomes at least twice broader than that for the pure IWM at the small velocity spread (≲1%) with a substantial contribution of the SWM. Moreover, the presence of the SWM reduces considerably the troublesome heat dissipation in the dielectric layer. Therefore, the mixed mode operation can allow up to several times more power than the usual IWM mode operation.
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52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
84.30.Le Amplifiers
52.75.-d Plasma devices
84.47.+w Vacuum tubes

Kα satellite spectra as diagnostics for particle beam‐target interaction

E. Nardi and Z. Zinamon

J. Appl. Phys. 52, 7075 (1981); http://dx.doi.org/10.1063/1.328415 (5 pages) | Cited 15 times

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Spectrometry of Kα radiation emitted during the interaction of an intense particle beam with matter is proposed as a diagnostic. Temperature measurement is possible through the detailed analysis of the Kα satellite spectrum. The role of line self‐absorption for this and other Kα measurements is discussed. The feasibility of such measurements is demonstrated in an electron beam‐target interaction experiment.
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52.40.Mj Particle beam interactions in plasmas
52.25.Kn Thermodynamics of plasmas
52.70.-m Plasma diagnostic techniques and instrumentation

The influence of a background plasma on the diocotron instability of a relativistic hollow electron beam

Henry J. Bilow and Han S. Uhm

J. Appl. Phys. 52, 7080 (1981); http://dx.doi.org/10.1063/1.328416 (6 pages) | Cited 2 times

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The influence of a background plasma on the diocotron instability of a relativistic hollow electron beam is investigated within the framework of a cold fluid model. The background plasma is taken to have a uniform density except at the mean radius of the electron beam where the density is assumed to be discontinuous. Of the charged species comprising the plasma, only the electrons influence the dynamics of the beam‐plasma system; the effect of the ions is negligible because of their small plasma frequency. A dispersion relation for the eigenfrequencies of the system is derived and employed to examine instabilities. It is found that the fundamental (l = 1) mode, which is unconditionally stable for a hollow electron beam in a vacuum, is now unstable for certain parameter regimes. The appearance or growth of instabilities with increases in the plasma density discontinuity is observed, while increases in the relativistic factor γb are seen to exert a stabilizing influence. It is also found that thin beams are generally more unstable than thick ones.
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52.40.Mj Particle beam interactions in plasmas
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.27.Ny Relativistic plasmas

Towards a high‐temperature solar electric converter

G. J. Dunning and A. J. Palmer

J. Appl. Phys. 52, 7086 (1981); http://dx.doi.org/10.1063/1.328417 (6 pages) | Cited 4 times

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The results of an experimental and theoretical study aimed at developing a novel high‐temperature solar electric converter are reported. The converter concept is based on the use of an alkali plasma to serve as both an efficient high‐temperature collector of solar radiation as well as the working fluid for a high‐temperature working cycle. The envisioned working cycle is a simple magnetohydrodynamic Rankine cycle. The motivation for developing this type of solar electric converter is based primarily on the cost and weight reduction premiums for operating a space solar electric generator at the maximum possible temperature. We report on the construction of a theoretical model for coupling sunlight into a cesium plasma and on the experimental demonstration of cesium heating with a solar simulator that is in good agreement with the theory.
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52.50.Gj Plasma heating by particle beams
84.60.Rb Thermoelectric, electrogasdynamic and other direct energy conversion

Numerical simulation of sheath structure and current‐voltage characteristics of a conductor‐dielectric disk in a plasma

R. C. Chaky, J. H. Nonnast, and J. Enoch

J. Appl. Phys. 52, 7092 (1981); http://dx.doi.org/10.1063/1.328744 (7 pages) | Cited 8 times

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We present results of a calculation of current‐voltage characteristic curves and voltage profiles for an idealized spacecraft charging configuration. We model a plasma interacting with a conducting disk covered by a charged dielectric, with a portion of the conductor exposed to the ambient magnetospheric plasma. We also model the electrostatics of a conducting ’’button’’ resting on the center of a dielectric disk. The calculation uses a cylindrical particle‐in‐cell (PIC) particle mover with variable particle number, and the potential is calculated self‐consistently using successive over relaxation (SOR). Results of this electrostatic plasma simulation are presented both with and without secondary electron emission from the dielectric.
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52.65.-y Plasma simulation
52.40.Hf Plasma-material interactions; boundary layer effects
84.60.Jt Photoelectric conversion
41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems

Heterodyne measurements of electron cyclotron emission from Alcator A and absolute submillimeter receiver calibration

P. Woskoboinikow, H. C. Praddaude, I. S. Falconer, and W. J. Mulligan

J. Appl. Phys. 52, 7099 (1981); http://dx.doi.org/10.1063/1.328418 (8 pages) | Cited 2 times

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Electron cyclotron emission (ECE) from thermal plasmas in the Alcator A tokamak for harmonics from 2nd through 5th and up to the 7th harmonic for nonthermal plasmas have been observed in the frequency range of 400–800 GHz using a sensitive, low‐noise submillimeter heterodyne receiver. The sensitivity of the receiver (∼10−20 W Hz−1) allowed for the measurement of 4th and 5th harmonic ECE from thermal plasmas with Te≊800 eV. The receiver was absolutely calibrated and its field of view was experimentally determined. A careful analysis has been made to relate the receiver calibration to the plasma‐emitting volume, taking into account radiation coherence time, wall reflections, polarization scrambling, window losses, and aperture restrictions.
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52.70.Gw Radio-frequency and microwave measurements
52.55.Fa Tokamaks, spherical tokamaks
52.55.Hc Stellarators, torsatrons, heliacs, bumpy tori, and other toroidal confinement devices
52.25.Kn Thermodynamics of plasmas
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Small energy loss rate of an electron and deexcitation of metastable molecules by superelastic collisions in high‐pressure oxygen glow discharge

Kanehiro Nobata and Soji Yamamoto

J. Appl. Phys. 52, 7107 (1981); http://dx.doi.org/10.1063/1.328419 (7 pages) | Cited 1 time

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Very small values of an electric field divided by pressure (E/P) were experimentally obtained in the positive column of the oxygen glow discharge at higher pressure where the positive column contracts. E/P was also measured in the nitrogen positive column for comparison. From both measured values of the electron temperature and E/P we find that the average fraction of the energy of an electron lost at each collision with an oxygen molecule becomes extremely small at higher pressures. The reason for this is investigated. The average fraction of electron energy lost by the inelastic collision for excitation to low lying metastable states is calculated. In this calculation the superelastic collision of an electron with a metastable molecule and the diffusion of the metastable molecules are both taken into account.
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52.80.Hc Glow; corona
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)

Lightning leader laboratory simulation by means of rectilinear surface discharges

S. Larigaldie, G. Labaune, and J. P. Moreau

J. Appl. Phys. 52, 7114 (1981); http://dx.doi.org/10.1063/1.328420 (7 pages) | Cited 8 times

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Gliding discharges over dielectric slabs can be made quasirectilinear by using a correctly shaped guiding electrode located behind the slab. Such guided discharges are characterized by the accessibility of their parameters to various diagnostic techniques, such as velocity, current, and voltage measurements, spectroscopy, and fast photography. In this paper the behavior of negative gliding‐surface discharges is studied with a view of understanding the behavior of the lightning leader. Theoretical predictions obtained by computation from a simplified model are compared with experimental data, and the result of this comparison is discussed.
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52.80.Pi High-frequency and RF discharges

Melting phenomena and pulsed‐laser annealing in semiconductors

J. Narayan, J. Fletcher, C. W. White, and W. H. Christie

J. Appl. Phys. 52, 7121 (1981); http://dx.doi.org/10.1063/1.328685 (8 pages) | Cited 21 times

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Annealing of displacement damage (amorphous as well as layers containing only dislocation loops), dissolution of boron precipitates, broadening of dopant profiles, and the formation of constitutional supercooling cells have been studied in laser annealed silicon. These samples were irradiated with laser pulses (λ = 0.485 μm, E = 0.7–1.25 J cm−2, τ = 9 ns), the same as those used by Compaan and coworkers for Raman temperature measurements. In contrast to their conclusion, present results can be interpreted only on the basis of a melting model.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
66.10.C- Diffusion and thermal diffusion
61.72.S- Impurities in crystals
61.72.U- Doping and impurity implantation

Asymmetric crystal topography of diacetylene and polydiacetylene macroscopic single crystals

Ronald G. Rosemeier, Robert E. Green, and Ray H. Baughman

J. Appl. Phys. 52, 7129 (1981); http://dx.doi.org/10.1063/1.328686 (7 pages) | Cited 5 times

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X‐ray transmission asymmetric crystal topography was used to investigate the changes in defect structure which occur during the solid‐state polymerization of macroscopic single crystals of a diacetylene. Comparison of x‐ray topographs made before and after gamma‐ray‐induced polymerization indicate that lattice strain increases during polymerization, but important defect structures present in monomer crystals are retained in the polymer crystals. A cross‐pattern defect structure along 〈201〉 crystallographic directions is typically observed in both monomer and polymer single crystals.
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81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Temperature dependence of amplitude‐dependent dislocation damping

A. V. Granato and Kurt Lücke

J. Appl. Phys. 52, 7136 (1981); http://dx.doi.org/10.1063/1.328687 (7 pages) | Cited 54 times

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A theory of the damping due to the break‐away of dislocations from pinning points given by the authors for low temperatures has been extended into the high‐temperature range by taking into account thermal activation during break‐away. It has been found that in the high‐temperature range the amplitude dependence is described by the same formula as in the low‐temperature range (Granato‐Lücke formula) but the parameters have a different meaning.
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61.72.Lk Linear defects: dislocations, disclinations
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)

Displacement criterion for amorphization of silicon during ion implantation

L. A. Christel, J. F. Gibbons, and T. W. Sigmon

J. Appl. Phys. 52, 7143 (1981); http://dx.doi.org/10.1063/1.328688 (4 pages) | Cited 58 times

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Results of Boltzmann transport equation calculations are used to estimate what fraction of a crystalline silicon lattice must be displaced to cause a crystalline‐to‐amorphous transition during ion implantation. Comparison of these calculations with experimental MeV He channeling and backscattering results for 150‐keV boron implantation at 77 °K indicates that the displacement of about 10% of the lattice will cause amorphization provided the substrate is at a temperature which inhibits self‐annealing processes and defect diffusion. The calculations also indicate that the number of atoms displaced is proportional to the deposited energy density, one displacement occurring on average for each 200 eV of deposited energy. Experimental results for room‐temperature silicon implantation confirm the fact that higher temperature substrates require a greater fractional displacement of the lattice before amorphization occurs.
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61.72.U- Doping and impurity implantation
64.70.K- Solid-solid transitions
63.70.+h Statistical mechanics of lattice vibrations and displacive phase transitions
61.80.Jh Ion radiation effects

Internal friction background and peaking effect

J. A. Caro and M. Mondino

J. Appl. Phys. 52, 7147 (1981); http://dx.doi.org/10.1063/1.328689 (8 pages) | Cited 10 times

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Internal friction results on poly‐ and single‐crystalline samples of 5 N Cu during irradiation at 350 K with 1.5 MeV electrons are presented. It is found that the peaking effect is a function of the total number of point defects created in the lattice and that it is independent of the frequency in the range 102–105 Hz. The amplitude dependence of peaking is shown to be related to the background amplitude dependence. Pulsed irradiation experiments indicate that no diffusion mechanism is involved in the initial increase of internal friction. It is then concluded that peaking is due to two effects, one from the bulk, responsible for the increase and the second, associated to the arrival of point defects at the dislocations and reducing their contribution to damping. The observation of peaking in single crystals at ϵ?10−6 indicates that sample structure only influences the strain amplitude level at which peaking appears but not its presence. A comparison with existing models allows one to conclude that a lattice dynamics approach provides the most satisfactory description of present results.
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61.80.Fe Electron and positron radiation effects
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
61.72.jd Vacancies
61.72.jj Interstitials

Characteristics of submicron pores obtained by chemical etching of nuclear tracks in polycarbonate films

G. Guillot and F. Rondelez

J. Appl. Phys. 52, 7155 (1981); http://dx.doi.org/10.1063/1.328690 (10 pages) | Cited 12 times

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Calibrated pores in the range 102–2×103 Å have been obtained by chemical etching of polycarbonate thin films irradiated with high energy krypton ions (500 MeV, Kr25+). Both the amorphous and the crystalline forms of polycarbonate (Makrofol, Bayer), further designated by their respective trade names N and KG, have been investigated up to thicknesses of 60 μm, close to the theoretical ion range of 77 μm. From conductivity studies, three different domains have been separated around the ion track: A highly damaged core of radius ?50 Å with a fast etching rate vT ≊104 Å/min, an intermediate zone of radius ?500 Å with an etching rate vI = 0.9 Å/min, an outer region with an etching rate equal to that of the undamaged material, vG = 0.47 Å/min. These observations are compatible with the delta ray model for track formation in plastic materials. Scanning electron microscope investigations have revealed that the pores formed in the N material are straight cylinders with a narrow distribution of the pore entrance diameters. On the other hand, the pores for the KG type are much less uniform and appear to be tapered, the difference between the two sides of the membrane being as much as 50%. These characteristics could be related to inhomogeneities in the morphological structure due to (i) the finite size of the crystalline domains and (ii) an asymetric manufacturer’s processing of the film surfaces.
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61.80.Jh Ion radiation effects
66.10.Ed Ionic conduction

Distribution of interatomic spacings in random alloys

Sverre Froyen and Conyers Herring

J. Appl. Phys. 52, 7165 (1981); http://dx.doi.org/10.1063/1.328691 (9 pages) | Cited 33 times

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In a disordered solid solution the interatomic spacings will vary because of fluctuations in the local environment. This paper extends previous theories of these variations for a system in which A and B atoms are distributed at random over the sites of a simple lattice, with atomic fractions x and (1−x), respectively, and for which the differences between A and B in regard to size and interaction characteristics are small enough to be treated in first order only. To this order exact results are derived regarding the statistics of relative positions of AA, AB, and BB near‐neighbor pairs: expressions are given especially for the departures for the average spacing of each of these three types of pairs from the corresponding spacing of the mean lattice, and for the mean‐square fluctuations of these relative positions about their means. The expressions can be evaluated from the elastic spectrum of the crystal and da/dx, the variation of the lattice constant with composition. For the common cubic lattices, graphs are given for their approximate numerical evaluation from da/dx and the three elastic constants. The elastic‐relaxation contribution to the configuration‐dependent energy can be evaluated from the same expressions.
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61.90.+d Other topics in structure of solids and liquids; crystallography (restricted to new topics in section 61)
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
61.72.Yx Interaction between different crystal defects; gettering effect

Dislocation‐free zone model of fracture

S.‐J. Chang and S. M. Ohr

J. Appl. Phys. 52, 7174 (1981); http://dx.doi.org/10.1063/1.328692 (8 pages) | Cited 79 times

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Recent observations by electron microscopy have shown that a dislocation‐free zone (DFZ) is present between the crack tip and the linear pileup of dislocations in the plastic zone. A singular integral equation is formulated to describe the equilibrium configuration of the dislocations. The distribution function of the dislocations is obtained in terms of elliptic integrals. The condition of compatibility and the elastic stress intensity factor at the crack tip are also derived. At the crack tip the stress varies as 1/√r. It is found that the stress intensity factor K is approximately a function of the length of the DFZ, whereas the externally applied stress approximately determines the length of the plastic zone. Based on the mechanism of dislocation generation at the crack tip proposed by Rice and Thomson, it is shown that the formation of the DFZ is anticipated when the stress intensity factor K is less than a critical stress intensity factor Kg defined for a spontaneous generation of dislocations. The magnitude of Kg relative to the critical stress intensity factor for brittle fracture Kc determines the brittle‐ductile nature of a material.
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62.20.M- Structural failure of materials
46.50.+a Fracture mechanics, fatigue and cracks
61.72.Lk Linear defects: dislocations, disclinations
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
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Polymorphic transitions in single crystals: A new molecular dynamics method

M. Parrinello and A. Rahman

J. Appl. Phys. 52, 7182 (1981); http://dx.doi.org/10.1063/1.328693 (9 pages) | Cited 1433 times

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A new Lagrangian formulation is introduced. It can be used to make molecular dynamics (MD) calculations on systems under the most general, externally applied, conditions of stress. In this formulation the MD cell shape and size can change according to dynamical equations given by this Lagrangian. This new MD technique is well suited to the study of structural transformations in solids under external stress and at finite temperature. As an example of the use of this technique we show how a single crystal of Ni behaves under uniform uniaxial compressive and tensile loads. This work confirms some of the results of static (i.e., zero temperature) calculations reported in the literature. We also show that some results regarding the stress‐strain relation obtained by static calculations are invalid at finite temperature. We find that, under compressive loading, our model of Ni shows a bifurcation in its stress‐strain relation; this bifurcation provides a link in configuration space between cubic and hexagonal close packing. It is suggested that such a transformation could perhaps be observed experimentally under extreme conditions of shock.
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64.70.K- Solid-solid transitions
61.50.Ks Crystallographic aspects of phase transformations; pressure effects

Reactivity of magnesium to hydrogen: A high‐pressure analysis of the dissolution enthalpy

R. Fromageau, J. Hillairet, E. Ligeon, C. Mairy, G. Revel, and P. Tzanétakis

J. Appl. Phys. 52, 7191 (1981); http://dx.doi.org/10.1063/1.328694 (5 pages) | Cited 4 times

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The temperature variation of the hydrogen solubility in magnesium in equilibrium with H2 gas has been measured mostly with use of a resistometric method, for pressures ranging between 0.1 and 12 MPa. The relative partial enthalpy per gram atom of the interstitially dissolved gas was inferred to be 58±5 kJ mol−1 (0.60±0.05 eV). This experimental finding is compared with previous data. The reaction of magnesium with traces of oxygen or moisture and the possible influence of this effect on the result are discussed also. A further point of discussion deals with the proper separation between hydrogen dissolution and hydride formation.
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64.75.-g Phase equilibria
66.30.J- Diffusion of impurities
61.72.S- Impurities in crystals
65.20.-w Thermal properties of liquids
65.40.gd Entropy
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