Materials Literature
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The unoccupied-states potential correction (USPC) in the local spin-density-functional (LSDF) formalism is proposed as a way to take correlation effects into account approximately. The method is based on using different potentials for the electrons in valence and conduction bands. When applied to antiferromagnetic tra…
A simple reflection technique for measuring the electro-optic coefficient of nonlinear optical polymeric films is described. The technique is based on the polarization rotation of a laser beam due to the electro-optic effect. It requires no waveguiding and can be used to measure polymeric films during, as well as afte…
Analyses of particle size distributions indicate that clay minerals and other diagenetic and metamorphic minerals commonly undergo recrystallization by Ostwald ripening. The shapes of their particle size distributions can yield the rate law for this process. One consequence of Ostwald ripening is that a record of the…
Abstract It has long been believed that the effectiveness of chemical inhibition of flow induced corrosion was limited by the prevailing flow rate or wall shear stress. The limitation is usually expressed in terms of a critical velocity calculated on the basis of API-RP-14E. At high flow rates and severe turbulence, a…
Pure hexagonal beta -Al 9 SiMn 3 does not order magnetically down to at least T=4.2 K. Recently the authors have studied beta -Al 9 Si(Mn 1-x Fe x ) 3 using Mossbauer effect spectroscopy with x=0.28 (1987 Phil. Mag. Lett. 56 143-51) and discovered a new transition at about 80 K. Here they present neutron diffraction s…
High resolution electrical resistivity measurements ( rho d rho /dT) are used to investigate in detail the two spin-reorientation transitions of the hexagonal ferromagnetic NdCo 5 compound which occur at T SR1 =242 K and T SR2 =283 K (T>T SR2 gives spontaneous magnetisation, M s , parallel to the c axis; T SR1 <T<T SR…
We show that finite-range matching rules and growth rules exist for an infinite set of 2D pentagonal tilings other than the original Penrose tilings. There is a natural ordering of these tilings based on the range required for the rules. The results have implications for the determination of the atomic structure of ic…
We report calorimetric measurements of the organic conductor (TMTSF${)}_{2}$${\mathrm{ClO}}_{4}$ in the quantum limit. In addition to the field-induced spin-density-wave (FISDW) phases, we have measured the magnetic-field-dependent specific heat associated with the recently discovered reentrant phase. In terms of a se…
Abstract Electrochemical polarization measurements were used to identify the mechanisms for the active dissolution of carbon steel by aqueous CO2 as a function of pH and temperature. Changes in the cathodic reaction mechanism with pH at 25°C were related directly to changes in CO2 speciation. At pH 2 through 4 the act…
The structure of TlGaSe2 has been studied by triple-crystal X-ray scattering techniques. At room temperature in the paraelectric phase the structure is believed to be C2/c, but the authors found that some of the (h, h, l) Bragg reflections, those with h odd, are broadened along the c* direction. This is shown to arise…
ABSTRACT In studying the flow of foam in unconsolidated porous media Khatib et al have shown that the destruction of foam lamellae depends on the gas/surfactant solution flowrates, fluid mobilities, and rock capillary pressure. This paper examines this flow regime, which we call the coalescence regime, in more detail.…
The influence of the interlayer coupling on the in-lane dynamics of stage-3 caesium-intercalated graphite is investigated. Comparison of the results from multi- and single-layer simulations shows that the in-plane dynamics are insensitive to the interlayer coupling. The single-particle dynamics, represented by the sel…
Abstract Polypropylene–maleic anhydride (PP–MA) graft copolymers were produced from isotactic homopolymer polypropylene (molecular weight > 150,000) utilizing the technique of solid phase graft copolymerization. A high degree of graft (about 8–10%) was achieved on 150 mesh (U.S. Standard Sieve) samples using this p…
Pure and high-quality single-crystal Nb(001) thin films with thicknesses ranging from 40 AA to 1000 AA were grown epitaxially on NaCl(001) substrates by an UHV E-beam evaporation technique. TEM observations, resistivity and superconducting transition temperature measurements were carried out. A drastic fall-off in tra…
Triboelectric charging between metals and insulators is usually thought to involve electron transfer. Doping some polymers with a small amount of salt can significantly change their charging properties, even reversing the sign to which they charge upon contact with a given metal. We show by means of secondary-ion mass…
In Ca 2 PO 4 Cl the Eu 2+ ion occupies two different crystallographic sites. The main difference between the sites is their size. The vibronic coupling strength of the 4f 7 to 4f 6 5d transition on Eu 2+ is very sensitive to this difference in size resulting in Huang-Rhys factors of S=3 and S=9 for the two sites. The…
Precise lattice spacing measurements are carried out with an X-ray double-source, double-crystal transmission technique in order to investigate the lattice distortions in silicon crystals containing oxygen impurities. A linear correlation between the absolute value of the lattice spacing and the oxygen concentration i…
The director-field configuration of a nematic liquid crystal confined to a spherical cavity within a urethane polymer is observed to transform from a radial- to axial-type structure as the radius of the cavity, temperature, or strength of an applied electric field are varied. The phase diagram, anchoring strength at t…
We address the problem of finding interatomic force fields for silicas from ab initio calculations on small clusters. It is shown that the force field cannot be determined from cluster data alone; incorporation of bulk-system information into the force field remains essential. Bearing this in mind, we derive a force f…
X-ray investigations were carried out on well-oriented liquid-crystal side-chain polymers of two series: (1) a polyacrylate-methylacrylate copolymer series with polar –CN end group and (2) the polyacrylate or polymethylacrylate with –OCH3 end group. To explain the diffraction phenomena a new fan-shaped model is sugges…