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Condensed Matter Physics

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Articles 2281 - 2310 of 2339

Full-Text Articles in Physical Sciences and Mathematics

Nife Invar Alloys: Theoretical Insights Into The Underlying Mechanisms Responsible For Their Physical Properties, Duane D. Johnson, F. J. Pinski, J. B. Staunton, B. L. Gyorffy, G. M. Stocks Jun 1989

Nife Invar Alloys: Theoretical Insights Into The Underlying Mechanisms Responsible For Their Physical Properties, Duane D. Johnson, F. J. Pinski, J. B. Staunton, B. L. Gyorffy, G. M. Stocks

Duane D. Johnson

What are the "driving forces" responsible for various physical properties of alloys? What causes alloy systems to order chemically and/or magnetically? To answer these questions, we have been using a quantum mechanical (QM) method to calculate cohesive energies, magnetic properties, and thermodynamic phase instability of alloys. This scheme directly incorporates the inherent disorder of the high-temperature solid solution and in this sense goes beyond traditional "band theory." Although approximations have been made at various steps in the thermodynamical averaging, and in the QM treatment of the electrons, adjustable parameters have not been used. Recently, for FCC NiFe (INVAR) alloys, we …

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Γ To X Transport Of Photoexcited Electrons In Type Ii Gaas/Alas Multiple Quantum Well Structures, Peter N. Saeta, John F. Federici, R. J. Fischer, Benjamin I. Greene, L. Pfeiffer, R. C. Spitzer, B. A. Wilson Apr 1989

Γ To X Transport Of Photoexcited Electrons In Type Ii Gaas/Alas Multiple Quantum Well Structures, Peter N. Saeta, John F. Federici, R. J. Fischer, Benjamin I. Greene, L. Pfeiffer, R. C. Spitzer, B. A. Wilson

All HMC Faculty Publications and Research

We report novel femtosecond time‐resolved measurements performed on staggered type II GaAs/AlAs multiple quantum well structures. Photoexcited electrons were determined to transfer from the Γ valley of the GaAs layers to the X valleys of the AlAs in 100 and 400 fs for 8‐ and 11‐monolayer‐thick GaAs samples, respectively.

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Continuum Model Of Thin-Film Deposition And Growth, Andrew J. Bernoff, Seth Lichter Jan 1989

Continuum Model Of Thin-Film Deposition And Growth, Andrew J. Bernoff, Seth Lichter

All HMC Faculty Publications and Research

A continuum theory for the deposition and growth of solid films is presented. The theory is developed in a coordinate-independent manner and so incorporates the fully nonlinear physics. The evolution of the film is modeled in three steps. First, the adsorption of atoms in the incident beam is modeled as a ballistic process. Second, the random motion of the adatoms is treated as a diffusive process. Finally, sticking of adatoms to the film occurs as a Poisson process. The resulting system of differential equations is examined in several parameter limits. The diffusively dominated limit appears similar to zone 1 of …

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Local Density Approximation Study Of Transition Andf-Electron Materials, Zhi Wei Lu Jan 1989

Local Density Approximation Study Of Transition Andf-Electron Materials, Zhi Wei Lu

Dissertations, Theses, and Masters Projects

The local density approximation (LDA) has been proved to be a powerful starting point for calculating electronic and structural properties for many real materials. We have studied the effects of particular forms of exchange-correlation potentials (the X{dollar}\alpha{dollar} and Hedin-Lundqvist form) upon the structural properties for the 3d Ti and 4d Zr using a highly accurate linearized augmented plane wave (LAPW) method. The calculated equilibrium volumes differ by 6-8% for these two forms (with X{dollar}\alpha{dollar} results in better agreement with experiment) with proportional differences in other structural properties, which we take to be an indication of the intrinsic reliability of the …

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Nmr On Single Crystals Of Potassium Cyanogen Bromide (A Measurement Of The Orientational Probability Distribution Function Of The Negatively Charged Cyanogen Ion), Jeffrey Howard Walton Jan 1989

Nmr On Single Crystals Of Potassium Cyanogen Bromide (A Measurement Of The Orientational Probability Distribution Function Of The Negatively Charged Cyanogen Ion), Jeffrey Howard Walton

Dissertations, Theses, and Masters Projects

Single crystals of K(CN)$\sb{\rm x}$/(Br)$\sb{\rm 1-x}$ enriched in $\sp{15}$N have been studied by $\sp{15}$N NMR. Because of the anisotropic chemical shift, the NMR frequency spectrum of the orientational glass state reflects the distribution of cyanide orientations. By studying the spectrum at many orientations of each crystal, the orientational probability distribution function P($\Omega$) has been determined for x = 0.50 and for x = 0.20. The probability function is largest along the (100) directions, intermediate in the (110) directions, and nearly 0 along the (111) directions. The NMR determined P($\Omega$) is presented graphically and in terms of the Kubic Harmonic functions. …

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Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson Dec 1988

Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson

Duane D. Johnson

A modification to Broyden’s method for obtaining stable and computationally efficient convergence in self-consistent calculations is developed and discussed. The method incorporates the advantages of two schemes proposed by Srivastava and by Vanderbilt and Louie without any increase in complexity. Its improvement over their methods is discussed. The present method is compared with two other widely used convergence methods, simple mixing and Anderson’s method, for the case of the disordered binary alloy Ni0.35Fe0.65 on the verge of a magnetic instability and is shown to be much improved in stability and rate of convergence.

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Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo Oct 1988

Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo

Alexander H. King

The role of interaction between slip dislocations and a Σ = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the Li2 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (1$\overline 1$1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the ($\overline 1$11) plane is predicted to …

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Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks Jan 1988

Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks

Duane D. Johnson

We present the results of first‐principles calculations of the total energy and spin‐polarized electronic structure of disordered fcc Fe0.50Mn0.50. These self‐consistent calculations were performed using the Korringa–Kohn–Rostoker method and the coherent‐potential approximation (KKR‐CPA), using the local‐spin‐density approximation to treat exchange and correlation. We use a lattice constant of a=6.80 a.u.; information about stability can be inferred from calculated pressure and energy. The moments on the Fe and Mn sites are large but antiparallel to each other, resulting in a small net magnetization. A comparison of the electronic structure is made for fcc Fe, Mn, and FeMn in both the ferromagnetic …

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Theoretical Study Of The Hyperfine Fields Of Ni And Fe In Fcc Ni,Fe, Alloys, H. Ebert, H. Winter, B. L. Gyorffy, Duane D. Johnson, F. J. Pinski Jan 1988

Theoretical Study Of The Hyperfine Fields Of Ni And Fe In Fcc Ni,Fe, Alloys, H. Ebert, H. Winter, B. L. Gyorffy, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

Using charge self-consistent cluster Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) band-structure calculations, the authors have studied the hyperfine fields on both Ni and Fe sites in the NixFe1-x alloys. To elucidate the influence of relativistic effects the hyperfine matrix elements have been calculated nonrelativistically as well as completely relativistically The dependence of the hyperfine fields on the environment of a given site has been studied by performing calculations for various atomic configurations around that site. The results of the work are compared with other theoretical data and with experiment.

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Spectral Momentum Density From Graphite From (E,2e) Spectroscopy: Comparison With First Principles Calculations, Chao Gao, A. L. Ritter, Jr Dennison, N. A. W. Holzwarth Jan 1988

Spectral Momentum Density From Graphite From (E,2e) Spectroscopy: Comparison With First Principles Calculations, Chao Gao, A. L. Ritter, Jr Dennison, N. A. W. Holzwarth

Journal Articles

We have measured the spectral momentum density p(E,q) of graphite by (e,2e) spectroscopy for momentum parallel and perpendicular to the crystal c axis. In the independent-electron approximation, p(E,q) = ΣG |Uk(G)|2 δ(q-k-G)δ(E-E(k)) where the one-electron wave function is Ψk(r) = eik•rΣGUk(G)eiG•r and G is a reciprocal-lattice vector. The measurements covered a range of momentum parallel to the c axis equal to 0 ≤ |q| ≤ 1.84Å-1 and a …

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Theoretical Study Of The Environmental Effects On The Hyperfine Fields Of Ni And Fe In Ni0.75fe0.25, H. Ebert, H. Winter, B. Gyorffy, Duane D. Johnson, F. J. Pinski Nov 1987

Theoretical Study Of The Environmental Effects On The Hyperfine Fields Of Ni And Fe In Ni0.75fe0.25, H. Ebert, H. Winter, B. Gyorffy, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

The dependence of the hyperfine fields Bhf of Ni and Fe in Ni0.75Fe0.25 on the surrounding atomic configuration has been studied by performing charge selfconsistent 6 shell-cluster Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) bandstructure calculations. By replacing the CPA- scatterers in the various shells around the central atom by Ni - or Fe-atoms, respectively, it could be shown that the hyperfine fields vary linearly with the number of Fe-atoms within a given shell and that the changes of Bhf due to simultaneous changes of the atomic configurations of different shells are additive. The changes of the hyperfine fields upon ordering of …

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The Further Geometry Of Grain Boundaries In Hexagonal Close-Packed Metals, Fu-Rong Chen, Alexander H. King Jan 1987

The Further Geometry Of Grain Boundaries In Hexagonal Close-Packed Metals, Fu-Rong Chen, Alexander H. King

Alexander H. King

A technique is given for finding partial DSC vectors appropriate to crystals with more than one atom per lattice site. The DSC lattice is made up of vectors that represent displacements of one crystal with respect to the other that leave the boundary structure shifted, but not complete. A new, rapid method for finding the step vectors associated with perfect DSC dislocations is described. Partial DSC vectors and step vectors for perfect DSC dislocations in hexagonal close-packed crystals are determined. The availability of reactions between lattice partial dislocations and grain boundaries in hexagonal close-packed crystals is also assessed.

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Interaction Between Magnetic And Compositional Order In Ni‐Rich Ni C Fe1−C Alloys (Invited), J. B. Staunton, Duane D. Johnson, B. L. Gyorffy Jan 1987

Interaction Between Magnetic And Compositional Order In Ni‐Rich Ni C Fe1−C Alloys (Invited), J. B. Staunton, Duane D. Johnson, B. L. Gyorffy

Duane D. Johnson

We have developed a first‐principles electronic theory of concentration fluctuations in spin polarized binary alloys. It is a mean field theory of the state of compositional order and it is based on the local spin density (LSD) approximation for describing the electrons. The usual averages over the statistical mechanical ensemble are carried out with the aid of the self‐consistent Korringe–Kohn–Rostoker coherent‐potential approximation (SCF‐KKR‐CPA). To illustrate the main consequences of the theory we study the compositional short‐range order in the Ni c Fe1−c alloy system. We find that the ordering energy is almost entirely of magnetic origin.

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Sites And Diffusion Of Muons In Fcc Metal Hydride Systems, James Russell Kempton Jan 1987

Sites And Diffusion Of Muons In Fcc Metal Hydride Systems, James Russell Kempton

Dissertations, Theses, and Masters Projects

A positive muon can be considered an isotope of hydrogen due to similarities in spin and charge. For metal hydride systems, the muon enters the sample "as the last hydrogen added," and competes for the same sites as the hydrogen atoms. to observe the site competition and diffusion of both particles (muon and proton), several FCC metal hydrides, TiH{dollar}\sb{lcub}1.83{rcub}{dollar}, TiH{dollar}\sb{lcub}1.97{rcub}{dollar}, TiH{dollar}\sb{lcub}1.99{rcub}{dollar}, YH{dollar}\sb{lcub}1.77{rcub}{dollar}, YH{dollar}\sb2{dollar}, ZrH{dollar}\sb{lcub}1.94{rcub}{dollar}, and LaH{dollar}\sb{lcub}2.06{rcub}{dollar}, were studied using transverse-, zero-, and low longitudinal-field {dollar}\mu{dollar}SR. The low temperature region results indicate that the muon predominately occupies octahedral sites for the FCC metal hydrides in this study. The probability for a …

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Photorefraction In Batio3, Stephen Ducharme Dec 1986

Photorefraction In Batio3, Stephen Ducharme

Stephen Ducharme Publications

This thesis summarizes the results of experimental investigations of the photorefractive properties of melt-grown BaTiO3 single crystals. Three basic photorefractive material properties are studied: (1) the effective density of photorefractive charges, (2) the photoconductivity of the photorefractive charges, and (3) the relative contributions of electron and hole photoconduction. Volume holographic measurement techniques are used: two-beam energy coupling, four-wave mixing, and erasure of volume holograms. The photorefractive properties were altered experimentally by chemically reducing or oxidizing a BaTiO3 crystal. I have extended the “hopping conduction” model of photorefractive transport to include simultaneous electron and hole photoconduction. The extension of …

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Ferromagnetism Versus Antiferromagnetism In Face-Centered-Cubic Iron, F. J. Pinski, J. Staunton, B. L. Gyorffy, Duane D. Johnson, G. M. Stocks May 1986

Ferromagnetism Versus Antiferromagnetism In Face-Centered-Cubic Iron, F. J. Pinski, J. Staunton, B. L. Gyorffy, Duane D. Johnson, G. M. Stocks

Duane D. Johnson

Using a first-principles disordered-local-moment picture of itinerant-electron magnetism, we calculated the temperature and volume dependence of the magnetic moment and spin-spin correlations for fcc Fe in the paramagnetic state.

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Density-Functional Theory For Random Alloys: Total Energy Within The Coherent-Potential Approximation, Duane D. Johnson, D. M. Nicholson, F. J. Pinski, B. L. Gyorffy, G. M. Stocks May 1986

Density-Functional Theory For Random Alloys: Total Energy Within The Coherent-Potential Approximation, Duane D. Johnson, D. M. Nicholson, F. J. Pinski, B. L. Gyorffy, G. M. Stocks

Duane D. Johnson

A density-functional-based theory is developed for calculation of the total energy and pressure of random substitutional alloys within the Korringa-Kohn-Rostoker coherent-potential approximation. The theory is used to calculate the concentration variation of the equilibrium lattice spacing of α-phase CucZn1−c alloys. We find, in agreement with experiment, that the variation is almost linear and that it deviates from Vegard's rule.

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Effect Of Strain On Muon Diffusion And Trapping In Metal By Bassam Salim Hitti, Bassam Salim Hitti Jan 1986

Effect Of Strain On Muon Diffusion And Trapping In Metal By Bassam Salim Hitti, Bassam Salim Hitti

Dissertations, Theses, and Masters Projects

Positive muons implanted in metal distort the surrounding lattice; therefore, in addition to electronic interactions, the elastic forces have to be considered in determining the muon state. to explore the elastic and electronic diffusion and trapping mechanisms, we studied AlCu(,420ppm), AlMg(,1000ppm) and AlAg(,1000ppm) alloys. These alloys were selected for the different effects on the host lattice of these impurities; Cu contracts the Al lattice, Mg expands it and Ag has nearly no effect. On the other hand Cu and Ag are monovalent while Mg is divalent. For AlCu between 5K and 14K the temperature exponent (beta) of the two-state-model trapping …

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A Nuclear Magnetic Resonance Study Of Deuterated Poly(Vinylidene Fluoride) And A Copolymer Of Deuterated Vinylidene Fluoride And Tetrafluoroethylene, Montee A. Doverspike Jan 1986

A Nuclear Magnetic Resonance Study Of Deuterated Poly(Vinylidene Fluoride) And A Copolymer Of Deuterated Vinylidene Fluoride And Tetrafluoroethylene, Montee A. Doverspike

Dissertations, Theses, and Masters Projects

Pulsed deuterium NMR experiments have been performed on deuterated samples of poly(vinylidene fluoride), PVF(,2), repeat unit CH(,2)CF(,2) and the copolymer poly(vinylidene fluoride)-tetrafluoroethylene (80-20), (PVF(,2)-F(,4)E). A deuterium line shape study has been employed to characterize the orientational distribution of the dipole moments in both poled and unpoled samples. In addition, the orientational distributions of chain axis alignment has been measured in stretched samples.;PVF(,2) and PVF(,2)-F(,4)E exhibit unique piezoelectric and pyroelectric properties which are due to their crystalline components (approximately 50% in typical material). Four crystalline phases exist in the homopolymer PVF(,2), the (alpha), (beta), (gamma), and the (delta). The relatively electrically …

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Determination Of The Vacancy Migration Energy Of Aluminum By Nmr, Terry William Gullion Jan 1986

Determination Of The Vacancy Migration Energy Of Aluminum By Nmr, Terry William Gullion

Dissertations, Theses, and Masters Projects

Monovacancy diffusion is a thermally activated process characterized by an activation energy E(,d). The diffusion of atoms requires the formation and migration of vacancies. The concentration of vacancies n/N is given by n/N (DBLTURN) exp(-E(,f)/kT). It can be shown that the activation energy E(,d) is the sum of the energy to form a vacancy E(,f) and the energy required for an atomic jump E(,m): E(,d) = E(,f) + E(,m). Furthermore, the atomic jump rate (omega)(,j) can be shown to be thermally activated and given by (omega)(,j) (DBLTURN) (nu)(,o)(n/N)exp(-E(,m)/kT) ((nu)(,o) is the attempt frequency).;NMR offers many techniques to measure the activation …

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Combined Translational-Rotational Jumps In Solid (Alpha)-Co And Co(,2), Shang-Bin Liu Jan 1985

Combined Translational-Rotational Jumps In Solid (Alpha)-Co And Co(,2), Shang-Bin Liu

Dissertations, Theses, and Masters Projects

Combined translational-rotational jumps in two orientationally ordered solids, (alpha)-CO and CO(,2), have been measured using C('13) NMR. In the Pa3 structure of these solids, a molecule which jumps to a neighboring (presumably vacant) site will reorient, due to the orientationally ordered structure.;The rates of translation and rotation have been measured independently by using different NMR techniques. The rotations were detected at high field (14.7 MHz) through the modulation of the chemical shift anisotropy; spin echoes and stimulated echoes were used. The translational jumps modulate the dipolar interactions and were studied at low fields (1.256 MHz) with line narrowing and Slichter-Ailion …

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First Principles Structure Calculations Using The General Potential Lapw Method, Su-Huai Wei Jan 1985

First Principles Structure Calculations Using The General Potential Lapw Method, Su-Huai Wei

Dissertations, Theses, and Masters Projects

We have developed a completely general first principles self-consistent full-potential linearized-augmented-plane-wave (LAPW) method program within the density functional formalism to calculate electronic band structure, total energy, pressure and other quantities. No symmetry assumptions are used for the crystal structure. Shape unrestricted charge densities and potentials are calculated inside muffin-tin (MT) spheres as well as in the interstitial regions. All contributions to the Hamiltonian matrix elements are completely taken into account. The core states are treated fully relativistically using the spherical part of the potential only. Scalar relativistic effects are included for the band-states, and spin-orbit coupling is included using a …

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Fast Method For Calculating The Self-Consistent Electronic Structure Of Random Alloys, Duane D. Johnson, F. J. Pinski, G. M. Stocks Nov 1984

Fast Method For Calculating The Self-Consistent Electronic Structure Of Random Alloys, Duane D. Johnson, F. J. Pinski, G. M. Stocks

Duane D. Johnson

We describe a computationally efficient method for performing self-consistent-field calculations of the electronic structure of random solid-solution alloys within the multiple-scattering coherent-potential-approximation formalism (KKR-CPA). We utilize a cluster method for solving the KKR-CPA equations and integrate along a contour in the complex-energy plane to reconstruct the single-site electronic densities.

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Acoustic Radiation-Induced Static Strain In Single Crystal Silicon, Ka Kui Peter Li Jan 1984

Acoustic Radiation-Induced Static Strain In Single Crystal Silicon, Ka Kui Peter Li

Dissertations, Theses, and Masters Projects

Quantitative verification of the existence of static acoustic displacements generated by acoustic waves propagating in single crystal samples of intrinsic silicon is presented. Measurements are made of the static displacements generated by 30 MHz acoustic compressional waves propagating along the 111 , 110 , and 100 crystalline directions. From these measurements the nonlinearity parameters are calculated and found to have the value 3.87 along the 111 direction, 4.23 along the 110 direction, and 2.13 along the 100 direction. These results are in agreement with values obtained independently from harmonic generation and pressure derivative measurements. Implications of the present work to …

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Thermal Propagation And Stability In Superconducting Films, Kenneth E. Gray, Robert T. Kampwirth, John F. Zasadzinski, Stephen P. Ducharme Jan 1983

Thermal Propagation And Stability In Superconducting Films, Kenneth E. Gray, Robert T. Kampwirth, John F. Zasadzinski, Stephen P. Ducharme

Stephen Ducharme Publications

Thermal propagation and stable hot spots (normal domains) are studied in various high Tc superconducting films (Nb3Sn, Nb, NbN and Nb3Ge). The prediction of the thermal propagation velocity of the long-standing model of Broom and Rhoderick (1960) is verified quantitatively in the regime of its validity. A new energy balance model is shown to give reasonable quantitative agreement of the dependence of the propagation velocity on the length of short normal domains. The steady state (zero velocity) measurements indicate the existence of two distinct situations for films on high thermal conductivity (sapphire) substrates. For low power per unit area the …

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Nmr Study Of Molecular Motions In Two Disordered Organic Solids, Philip L. Kuhns Jan 1983

Nmr Study Of Molecular Motions In Two Disordered Organic Solids, Philip L. Kuhns

Dissertations, Theses, and Masters Projects

The molecular motions are studies in two disordered materials that undergo glass transitions. Glycerol is a conventional glass former and cyclohexanol is an orientational glass former.;The technique used in the glycerol experiments was spectral hole burning. Chemical shift anisotropy produces inhomogeneous broadening of NMR lines in orientationally disordered and polycrystalline solids. By saturating or inverting a portion of the anisotropic line, 'burning a hole', molecules of certain orientations are tagged. Subsequent molecular reorientations result in spectral diffusion which is not related to spin-spin interactions. By measuring the broadening and recovery of the hole as a function of time, detailed knowledge …

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Diffusion And Trapping Of Positive Muons In Niobium And In Aluminum Alloys, Muhammad Zillulhaq Numan Jan 1982

Diffusion And Trapping Of Positive Muons In Niobium And In Aluminum Alloys, Muhammad Zillulhaq Numan

Dissertations, Theses, and Masters Projects

Zero, longitudinal and transverse magnetic field uSR has been used to investigate (mu)('+) diffusion and trapping in Nb. The ambiguity in the interpretation of the 'double humped' temperature dependence of the depolarisation rate for the transverse field case has been resolved. A discussion of how the zero and longitudinal measurements can distinguish between the trapping and detrapping phenomena is presented with (mu)SR data analysis in mind. Muon mobility is shown to increase monotonically with temperature. The width of the local magnetic field distribution due to Nb nuclear moments and the rate for trapping and detrapping of muons have been measured …

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A [Mu]+Srstudy Of Uniaxial Stress Induced Symmetry Breaking In An Fe Single Crystal, Min. Namkung Jan 1982

A [Mu]+Srstudy Of Uniaxial Stress Induced Symmetry Breaking In An Fe Single Crystal, Min. Namkung

Dissertations, Theses, and Masters Projects

For the first time, external uniaxial stress has been used in a (mu)('+)SR experiment. The stress dependences of the following parameters were obtained for Fe crystals: the muon precessional frequency, (nu)(,(mu)), the transverse (longitudinal) depolarization rates, 1/T(,2) (1/T(,1)), and F(,T)/F(,L), the ratio of the probabilities for the muon to find domains with transverse/longitudinal fields. The shift in (nu)(,(mu)) was -0.34 (+OR-) 0.023 MHz per 100 micro-strain along the -axis. Changes in other parameters depend on the sample history but they, in general, increase with stress.;External stress changes the muon occupational probability at each site which significantly affects the dipolar field …

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Phosphorus-31 Knigh Shifts In Amorphous Nickel-Phosphorus And Nickel-Cobalt-Phosphorus Alloys, Paul Stuart Gustafson Jan 1981

Phosphorus-31 Knigh Shifts In Amorphous Nickel-Phosphorus And Nickel-Cobalt-Phosphorus Alloys, Paul Stuart Gustafson

Dissertations, Theses, and Masters Projects

Amorphous alloys of the form Ni(,1-x)P(,x) and (Ni(,1-y)Co(,y))(,1-x)P(,x) were prepared by two methods, electroplating (EP) and electroless deposition (EL). Two metastable phases of differing physical densities and NMR properties were noted, and analysed by measurement of the Knight Shifts, relaxation times, physical densities, etc. A comparison is made between the data and a hybridized band model which yields an expression for the enhanced susceptibility of the phosphorous valence band.

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Ultrasonic Determination Of Thermoelastic Properties Of Stressed Solids, Engmin J. Chern Jan 1981

Ultrasonic Determination Of Thermoelastic Properties Of Stressed Solids, Engmin J. Chern

Dissertations, Theses, and Masters Projects

We present a thermoelastic derivation of ultrasonic waves propagating in a solid in which an applied homogeneous stress is superimposed on a nonzero initial stress. We also derive the temperature dependence of the elastic coefficients and the linear relationship between the applied stress and a newly defined parameter--the thermal acoustic constant. The stress acoustic constant is defined and its relationship to the acoustic natural velocity is discussed. Experimental considerations pertinent to the ultrasonic measurement techniques used in the investigation are described. The results of the stress-strain and thermal strain experiments verify the predictions of the theory. Finally, we derive an …

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