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Articles 31  60 of 342
FullText Articles in Physics
Aligned TwoPhase Magnets: Permanent Magnetism Of The Future? (Invited), Ralph Skomski
Aligned TwoPhase Magnets: Permanent Magnetism Of The Future? (Invited), Ralph Skomski
Ralph Skomski Publications
Micromagnetic calculations are used to investigate coercivity and energy products of magnets consisting of an aligned hardmagnetic skeleton phase and a softmagnetic phase with high saturation magnetization. Compared to the presentday theoretical limit of 516 W/m^{3} for singlephase Nd_{2}Fe_{14}B, the energy product in suitable nanostructured Sm_{2}Fe_{2}N_{3}/Fe_{65}Co_{35} composites is predicted to be as high as 1090 kJ/m3. The influence of the skeleton’s texture and shape is discussed, and aligned nanocrystalline twophase magnets are compared with remanenceenhanced isotropic magnets. In particular, it is shown how ...
Recent Developments In Modeling Of The Stress Derivative Of Magnetization In Ferromagnetic Materials, David C. Jiles, Michael K. Devine
Recent Developments In Modeling Of The Stress Derivative Of Magnetization In Ferromagnetic Materials, David C. Jiles, Michael K. Devine
Ames Laboratory Publications
The effect of changing stress on the magnetization of ferromagnetic materials leads to behavior in which the magnetization may increase, or decrease, when exposed to the same stress under the same external conditions. A simple empirical law seems to govern the behavior when the magnetization begins from a major hysteresis loop. The application of the law of approach, in which the derivative of the magnetization with respect to the elastic energy supplied dM/dW is proportional to the magnetization displacement M _{an}−M, is discussed.
Frequency Dependence Of Hysteresis Curves In Conducting Magnetic Materials, David C. Jiles
Frequency Dependence Of Hysteresis Curves In Conducting Magnetic Materials, David C. Jiles
Ames Laboratory Publications
An extension of the hysteresis model has been developed that takes into account the effects on the hysteresis curves of eddycurrents in electrically conducting media. In the derivation presented it is assumed that the frequency of the applied field is low enough (or the thickness of the material medium small enough) that the skin effect can be ignored so that the magnetic field penetrates uniformly throughout the material. In this case, the dc hysteresis equation is extended by the addition of a classical eddy‐current‐loss term depending on (i) the rate of change of magnetization with time, (ii) the ...
Iron Core Formation In Horse Spleen Ferritin: Magnetic Susceptibility, Ph, And Compositional Studies, S. Hilty, B. Webb, Richard B. Frankel, G. D. Watt
Iron Core Formation In Horse Spleen Ferritin: Magnetic Susceptibility, Ph, And Compositional Studies, S. Hilty, B. Webb, Richard B. Frankel, G. D. Watt
Physics
Horse spleen ferritin (HoSF) reconstituted with small iron cores ranging in size from 8 to 500 iron atoms was studied by magnetic susceptibility and pH measurements to determine when the added Fe^{3+} begins to aggregate and form antiferromagnetically coupled clusters and also to determine the hydrolytic state of the iron at low iron loading. The Evans NMR magnetic susceptibility measurements showed that at iron loadings as low as 8 Fe^{3+}/HoSF, at least half of the added iron atoms were involved in antiferromagnetic exchange interactions and the other half were present as isolated iron atoms with S = 5 ...
Electron Energy Loss In Oxygen Plasmas, G. A. Victor, John C. Raymond, Jane L. Fox
Electron Energy Loss In Oxygen Plasmas, G. A. Victor, John C. Raymond, Jane L. Fox
Jane L. Fox
The results of calculations of the energy deposition of energetic electrons in oxygen plasmas are given. In a pure oxygen plasma even with large fractional ionization, much of the electron energy results in the production of additional ionization and excited electronic states. Results are given for separate calculations using theoretical and experimental cross sections for the important O I excitations of ^{1}S and ^{1}D because the theoretical and experimental data are not in agreement. These results are useful for understanding the spectra of oxygenrich supernova remnants.
Matched Optical Solitary Waves For 3Level And 5Level Systems, Foek T. Hioe, R. Grobe
Matched Optical Solitary Waves For 3Level And 5Level Systems, Foek T. Hioe, R. Grobe
Physics Faculty/Staff Publications
Exact analytic results are presented that give a general solution for a pair of solitary waves which can propagate through a three and a fivelevel system with their shapes invariant. These solitary waves vary widely in shape and form: from ones for which the pulses have similar shape to ones which have very different but ''complementary'' shapes. A general type of solitarywave pair which is insensitive to small perturbations is identified.
Nanostructures Of SmCo On Cr Thin Films, Yi Liu, B. W. Robertson, Z.S. Shan, S. Malhotra, M.J. Yu, S.K. Renukunta, Sy_Hwang Liou, David J. Sellmyer
Nanostructures Of SmCo On Cr Thin Films, Yi Liu, B. W. Robertson, Z.S. Shan, S. Malhotra, M.J. Yu, S.K. Renukunta, Sy_Hwang Liou, David J. Sellmyer
SiHwang Liou Publications
The nanostructures of SmCo on Cr thin films prepared by dc magnetron sputtering were investigated by high resolution transmission electron microscopy (HRTEM) and diffraction techniques. HRTEM micrographs show that the crystallites in the SmCo films, as revealed by the lattice fringes, are distributed discontinuously in the matrix. The matrix is amorphous as indicated by the microdiffraction study. The size of the crystallites is in the range of 2~5 nanometers. The volume fraction of the crystallites in the film decreases from 91% to 54% as the argon pressure is increased from 5 mTorr to 30 mTorr. Micrographs recorded in a ...
BinaryEncounterDipole Model For ElectronImpact Ionization, YongKi Kim, M. Eugene Rudd
BinaryEncounterDipole Model For ElectronImpact Ionization, YongKi Kim, M. Eugene Rudd
M. Eugene Rudd Publications
A theoretical model, which is free of adjustable or fitted parameters, for calculating electron impact ionization cross sections for atoms and molecules is presented. This model combines the binaryencounter theory with the dipole interaction of the Bethe theory for fast incident electrons. The ratios of the contributions from distant and close collisions and interference between the direct and exchange terms are determined by using the asymptotic behaviors predicted by the Bethe theory for ionization and for stopping cross sections. Our model prescribes procedures to calculate the singly differential cross section (energy distribution) for each subshell using the binding energy, average ...
Mössbauer, Magnetic, And ElectronicStructure Studies Of Yfe_{12X}Mo_{X} Compounds, I.A. AlOmari, Sitaram Jaswal, A.S. Fernando, David J. Sellmyer, H.H. Hamdeh
Mössbauer, Magnetic, And ElectronicStructure Studies Of Yfe12XMoX Compounds, I.A. AlOmari, Sitaram Jaswal, A.S. Fernando, David J. Sellmyer, H.H. Hamdeh
David Sellmyer Publications
Mössbauer spectra, magnetization measurements, and selfconsistent spinpolarized electronic structures of YFe_{12x}Mo_{x}, where x=0.5, 1.0, 2.0, 3.0, and 4.0, are reported. The ternary compounds YFe_{12x}Mo_{x} have the crystalline tetragonal ThMn_{12} structure. Analyses of the Mössbauer spectra show that Mo atoms occupy the 8i Fe sites of the ThMn_{12} structure, in agreement with previous observations. Roomtemperature magnetic and Mössbauer measurements show that the compounds with x≤2.0 are ferromagnetic and with x≥3.0 are paramagnetic. Measurements at 25 K show that all the samples are magnetically ...
Measurements Of The (E,E’Pπ) Reaction On Nuclei In The Nucleon Resonance Region, L Elouadrhiri, R A. Miskimen, J ButtonShafer, P Degtyarenko,, Gerald Alvin Peterson, S Shuvalov, K Wang
Measurements Of The (E,E’Pπ) Reaction On Nuclei In The Nucleon Resonance Region, L Elouadrhiri, R A. Miskimen, J ButtonShafer, P Degtyarenko,, Gerald Alvin Peterson, S Shuvalov, K Wang
Gerald Alvin Peterson
Nucleon resonances beyond the Δ(1232) have been observed in complex nuclei. Measurements of the (e,e’pπ) reaction, at an incident energy of 14.5 GeV with 1.1 GeV
Measurements Of The Electric And Magnetic Form Factors Of The Proton From Q2=1.75 To 8.83 (Gev/C)2, L Andivahis, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson, S Rokni
Measurements Of The Electric And Magnetic Form Factors Of The Proton From Q2=1.75 To 8.83 (Gev/C)2, L Andivahis, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson, S Rokni
Gerald Alvin Peterson
The proton elastic form factors GEp(Q2) and GMp(Q2) have been extracted for Q2=1.75 to 8.83 (GeV/c)2 via a Rosenbluth separation to ep elastic cross section measurements in the angular range 13°≤θ≤90°. The Q2 range covered more than doubles that of the existing data. For Q2<4 >(GeV/c)2, where the data overlap with previous measurements, the total uncertainties have been reduced to < 14% in GEp and < 1.5% in GMp. Results for GEp(Q2) are consistent with the dipole fit GD(Q2)=(1+Q2/0.71)2, while those for GMp(Q2)/μpGD(Q2) decrease smoothly from 1.05 to 0.92. Deviations from form factor scaling are observed up to 20%. The ratio Q2F2/F1 is observed to approach a constant value for Q2>3 (GeV/c)2. Comparisons are made to vector meson dominance, dimensional scaling, QCD sum rule, diquark, and constituent quark models, none of which fully characterize all the new ...
Anisotropy And MagnetoOptical Properties Of Sputtered Co/Ni Multilayer Thin Films, Y.B. Zhang, John A. Woollam, Z.S. Shan, J.X. Shen, David J. Sellmyer
Anisotropy And MagnetoOptical Properties Of Sputtered Co/Ni Multilayer Thin Films, Y.B. Zhang, John A. Woollam, Z.S. Shan, J.X. Shen, David J. Sellmyer
David Sellmyer Publications
Several series of sputtered Co/Ni multilayer thin films have been investigated. The volume and interface contributions to the magnetic anisotropy were determined from magnetization measurements, and the interface anisotropy, K_{i}= 0.23 ± 0.03 erg/cm^{2}, was found to support perpendicular magnetic anisotropy. The anisotropy constant, K, increased with the Au buffer layer thickness, indicating the buffer layer was crucial to the perpendicular magnetic anisotropy. The polar Kerr rotation and coercivity as a function of temperature, and room temperature magnetooptical figure of merit are presented in this paper.
MeanField Theory For AlkaliMetalDoped Polyacetylene, A. Brooks Harris
MeanField Theory For AlkaliMetalDoped Polyacetylene, A. Brooks Harris
Department of Physics Papers
The Landau theory used by Choi and Mele (CM) to treat their rotor model on a triangular lattice for the orientational ordering of polyacetylene chains in alkalimetaldoped polyacetylene is studied. A reanalysis of the higherorder terms in the Landau expansion indicates that cosine ordering can support a nonzero cubic term in the Landau expansion whereas the sineordered phase has no such term. To construct a phase diagram requires a numerical solution of the selfconsistent equations of meanfield theory. Although this analysis does not convincingly treat the incommensurate phases found by CM, it does identify an unusually rich variety of thermodynamically ...
Comment On "Critical Behavior Of The Coulomb Glass", Thomas Vojta, Michael Schreiber
Comment On "Critical Behavior Of The Coulomb Glass", Thomas Vojta, Michael Schreiber
Physics Faculty Research & Creative Works
No abstract provided.
Cosmological And Wormhole Solutions In LowEnergy Effective String Theory, Mariano Cadoni, Marco Cavaglia
Cosmological And Wormhole Solutions In LowEnergy Effective String Theory, Mariano Cadoni, Marco Cavaglia
Physics Faculty Research & Creative Works
We derive and study a class of cosmological and wormhole solutions of lowenergy effective string field theory. We consider a general fourdimensional string effective action where moduli of the compactified manifold and the electromagnetic field are present. The cosmological solutions of the twodimensional effective theory obtained by dimensional reduction of the former are discussed. In particular we demonstrate that the twodimensional theory possesses a scalefactor duality invariance. Eucidean fourdimensional instantons describing the nucleation of the baby universes are found and the probability amplitude for the nucleation process given.
Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓAlₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow
Neutron Diffraction And Mössbauer Effect Study Of Several Nd₂Fe₁₇₋ₓAlₓ Solid Solutions, William B. Yelon, H. Xie, Gary J. Long, Oran Allan Pringle, Fernande Grandjean, K. H. J. Buschow
Physics Faculty Research & Creative Works
Aluminumsubstituted Nd_{2}Fe_{17x}Al_{x} solid solutions with x=2.30, 4.44, 6.13, 8.00, and 9.40 have been studied by neutron diffraction and Mössbauer spectroscopy. A Rietveld analysis of the neutron scattering indicates that the aluminum atoms have a high initial affinity for the 18h site, show a high affinity for the 6c site at high aluminum concentrations, and are absent from the 9d site at all aluminum concentrations. The Mössbauer spectra show a maximum in both the maximum and weighted average hyperfine field for x≅2. This indicates that the lattice expansion which ...
Interaction Of A Group Of Dislocations Within The Framework Of The Continuum FrenkelKontorova Model, Naum I. Gershenzon
Interaction Of A Group Of Dislocations Within The Framework Of The Continuum FrenkelKontorova Model, Naum I. Gershenzon
Physics Faculty Publications
The FrenkelKontorova (FK) model of edge dislocation is analyzed. Solutions of the continuum limit of the FK model [the sineGordon (SG) equation] are obtained in a form convenient for investigation of dynamics of a large number of interacting dislocations. We consider, based on these solutions, some nonstationary processes: dislocation generation, diffusion of dislocations, and crackdislocation interaction. Simple relations connecting the velocity of plastic deformation, density and velocity of dislocations, and the force of interaction between dislocations are obtained. The nucleation of dislocations at a moving crack tip is described.
Driven Front And Interface Of A FluidFlow Model In 2+1Dimensions, Michael J. Leaseburg, Ras B. Pandey
Driven Front And Interface Of A FluidFlow Model In 2+1Dimensions, Michael J. Leaseburg, Ras B. Pandey
Faculty Publications
Computer simulations are performed to study the motion of the front and the growth of the interface width in a model of fluid flow driven by a biased field in 2+1 dimensions. The initial motion of the front is diffusive, which is followed by a nondiffusive powerlaw behavior in the longtime regime; the powerlaw exponent is nonuniversal, varying with the strength of the driven field. The growth of the interface width saturates in the asymptotic time regime. The saturated width W scales with both the driven field B as well as the transverse length L of the sample, leading ...
Estimation Of The FreeChargeCarrier Concentration In FastIon Conducting Na2sB2s3 Glasses From An Analysis Of The FrequencyDependent, Ernest F. Hairetdinov, Nikolai F. Uvarov, Hitendra K. Patel, Steve W. Martin
Estimation Of The FreeChargeCarrier Concentration In FastIon Conducting Na2sB2s3 Glasses From An Analysis Of The FrequencyDependent, Ernest F. Hairetdinov, Nikolai F. Uvarov, Hitendra K. Patel, Steve W. Martin
Materials Science and Engineering Publications
ac and dc conductivities of fastion conducting xNa2S+(1x)B2S3 glasses in the composition range 0.001≤x≤0.1 were analyzed using the AlmondWest formula σ(ν)=σdc[1+(ν/νH)α]. The hopping frequency for free charge carriers νH, the dc conductivity σdc, and their respective activation energies were determined. The concentration of free charge carriers evaluated from the conductivities and estimated mobilities is in good agreement with the overall content of sodium cations in the glasses and it is proposed that this supports the concept of a strong and not weak electrolyte model for these ...
ThreeBody Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra
ThreeBody Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra
Chemistry Faculty Publications
Large basis set ab initio calculations have been carried out for a dense grid of points on the He, potential energy surface. Threebody contributions were extracted at every point, and a number of concise functional representations for the threebody potential surface were then examined. Threebody multipolar dispersion terms and other radial and angular terms were used in the representations, and an assessment of relative importance of the different terms is presented. Combined with a twobody HeHe potential, the results of this work should offer a high quality interaction potential for simulations of aggregated helium.
A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of The Nd₂Fe₁₇₋ₓAlₓ Solid Solutions, Gary J. Long, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean
A Magnetic, Neutron Diffraction, And Mössbauer Spectral Study Of The Nd₂Fe₁₇₋ₓAlₓ Solid Solutions, Gary J. Long, Gaya Kanishka Marasinghe, Sanjay R. Mishra, Oran Allan Pringle, Zhongbo Hu, William B. Yelon, D. P. Middleton, K. H. J. Buschow, Fernande Grandjean
Chemistry Faculty Research & Creative Works
The magnetic properties of a series of Nd_{2}Fe_{17x}Al_{x} solid solutions, with x equal to 2.04, 4.01, 5.97, 7.94, and 9.06, have been studied by magnetic measurements, neutron diffraction, and Mössbauer spectroscopy. Magnetization studies indicate that the Curie temperature increases from 330 K in Nd_{2}Fe_{17} to a maximum of ~470 K at an x of 3.5. The compounds crystallize in the Th_{2}Zn_{17} structure with lattice parameters and unit cell volumes which increase linearly with increasing aluminum content. The neutron diffraction results indicate that aluminum ...
Subthreshold Channel Leakage Current In Gaas Mesfet's, Wei Long
Subthreshold Channel Leakage Current In Gaas Mesfet's, Wei Long
Theses
In this thesis, a physical model including the subthreshold conpensation properties is presented. The Poisson equation is solved analytically in one dimension for GaAs MESFET's with undoped substrates in the subthreshold region. The solution is then used to derive expressions for subthreshold drain current and subshreshold swing in MESFET's with undoped substrates. Very good agreement between experimental and analytical results is achieved.
Two key parameters (Nilo and Iso) that determine the subthreshold Characteristics have been analyzed as a function of residual acceptor concentration Na, deep level EL2 concentration Nt, channel doping concentration Nd and threshold voltage Vt. It ...
Measurement Of The Hall Coefficient And Electron Mobility Using Van Der Pauw Type Hall Effect Measurements, HongSheng Luo
Measurement Of The Hall Coefficient And Electron Mobility Using Van Der Pauw Type Hall Effect Measurements, HongSheng Luo
Theses
Hall effect measurement in the electrical characterization of semiconductor materials is very important. We set up the Hall effect measurement system and examined the system with a standard sample. The experimental results show that this Hall measurement system worked as well as expected. We also used this system to study the GaAs/GaAs and InGaAs/GaAs which grown by MBE. Finally, we disscussed and consided some common problems of Hall measurement. Some useful formulas and plots are presented.
Mbe Growth Of Inxga1Xas/Gaas/Si Heterostructure System, Jun Liu
Mbe Growth Of Inxga1Xas/Gaas/Si Heterostructure System, Jun Liu
Theses
In this work, we grew the In_{x}Ga_{1x}As/GaAs/Si (GaAs as buffer layer) by MBE technique. The surface of the buffer layer became microscopically rough as the thickness of the buffer layer increased and the growth mode of GaAs on Si underwent a change from threedimensional to twodimensional during the initial growth stage as indicated on the Reflection High Energy Electron Diffraction (RHEED) screen. The Scattering Electron Microscopy (SEM) observation of the etched surface of GaAs on Si showed that the structure of the buffer layer tended to be polycrystalline and it was possible that a ...
Resonant Photoemission Studies Of Thickness Dependence Of The Unoccupied Gd 5d Bands, Peter A. Dowben, Dongqi Li, Jiandi Zhang, M. Onellion
Resonant Photoemission Studies Of Thickness Dependence Of The Unoccupied Gd 5d Bands, Peter A. Dowben, Dongqi Li, Jiandi Zhang, M. Onellion
Peter Dowben Publications
Ultrathin Gd films have been studied with constant initialstate spectroscopy (CIS) of photoemission utilizing linearly polarized light of synchrotron radiation. The photoemission crosssection of the 5d surface state near EF shows strong photon energy dependence, i.e., sharp peaks in CIS spectra near the Gd 5p_{1/2} adsorption edge. These peaks originate from resonant photoemission processes involving the occupied 5p and unoccupied 5d levels of the surface atoms. The symmetry of the unoccupied states were determined experimentally by changing the polarization of light, where ppolarized light excites only to the unoccupied d_{z2} or d_{xz,yz} states ...
Particle Conjugation And The 1/N_C Corrections To G_A, Joseph Schechter, H. Weigel
Particle Conjugation And The 1/N_C Corrections To G_A, Joseph Schechter, H. Weigel
Physics
We impose the requirement that the isovector axial vector current for the soliton sector of the chiral quark model transforms correctly under particle conjugation. This forces us to choose an otherwise arbitrary ordering of collective space operators in such a way that the nexttoleading 1/N_C correction to g_A vanishes.
On The Discretized Light Cone Quantization Of Electrodynamics, Alex C. Kalloniatis, David G. Robertson
On The Discretized Light Cone Quantization Of Electrodynamics, Alex C. Kalloniatis, David G. Robertson
Physics Faculty Scholarship
Discretized lightcone quantization of (3+1)dimensional electrodynamics is discussed, with careful attention paid to the interplay between gauge choice and boundary conditions. In the zero longitudinal momentum sector of the theory a general gauge fixing is performed, and the corresponding relations that determine the zero modes of the gauge field are obtained. One particularly natural gauge choice in the zero mode sector is identified, for which the constraint relations are simplest and the fields may be taken to satisfy the usual canonical commutation relations. The constraints are solved in perturbation theory, and the Poincaré generators Pμ are constructed. The ...
Spontaneous Structure Formation In Driven Systems With Two Species: Exact Solutions In A MeanField Theory, I. Vilfan, R. K. P. Zia, Beate Schmittmann
Spontaneous Structure Formation In Driven Systems With Two Species: Exact Solutions In A MeanField Theory, I. Vilfan, R. K. P. Zia, Beate Schmittmann
Beate Schmittmann
A stochastic lattice gas of particles, subject to an excluded volume constraint and to a uniform external driving field, is investigated. Using a meanfield theory for a system with equal number of oppositely charged particles, exact results are obtained. Focusing on the currentvsdensity plot, we propose an explanation for the discontinuous transition found in earlier simulations. A critical value of the drive, below which this transition becomes continuous, is found. These results are supported by a bifurcation analysis, leading to an equation of motion for the amplitude of the soft mode.
Excited Heavy Baryons In The Bound State Picture, Joseph Schechter, Anand Subbaraman
Excited Heavy Baryons In The Bound State Picture, Joseph Schechter, Anand Subbaraman
Physics
The orbitally excited heavy quark baryons are studied in the Callan Klebanov bound state model with heavy spin symmetry. First, a compact description of the large N_c, infinite heavy quark mass bound state wavefunctions and the collective quantization is given. In order to study the kinematical corrections due to finite masses we motivate an approximate Schrodingerlike equation for the bound state. The effective potential in this equation is compared with the quadratic approximation (spherical harmonic oscillator) to it. This oscillator approximation is seen to be not very accurate. It is noted that the present experimental information cannot be even qualitatively ...
Crystallography And Magnetism Of The HeavyFermion Compound Ybbipt, R. A. Robinson, A. Purwanto, M. Kohgi, Paul C. Canfield, T. Kamiyama, T. Ishigaki, J. W. Lynn, R. Erwin, E. Peterson, R. Movshovich
Crystallography And Magnetism Of The HeavyFermion Compound Ybbipt, R. A. Robinson, A. Purwanto, M. Kohgi, Paul C. Canfield, T. Kamiyama, T. Ishigaki, J. W. Lynn, R. Erwin, E. Peterson, R. Movshovich
Physics and Astronomy Publications
The superheavyfermion compound YbBiPt has the largest known linear specificheat coefficient γ=8 J mol−1 K−2, and the source of this enormous ‘‘electronic’’ specific heat is of great current interest. Here we describe neutrondiffraction studies that indicate its previously reported crystallographic structure to be incorrect. We find that the Pt atom is on the unique site and can be thought of as an interstitial in a fictitious rocksalt structure YbBi, which can in turn be thought of as an ordered form of elemental bismuth. We find no evidence of disorder between sites, occupancy on the nominally vacant site ...