Materials Literature
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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…
Cu 2 P 2 O 7−α cristallise dans C2/c avec a=6,895, b=8,113, c=9,164 A, β=109,62, Z=4; affinement jusqu'a R=0,036. Les polyedres de CuO 5 sont connectes et forment des couches en (001), qui sont liees par des groupes P 2 O 7 ; P−O terminal =1,497, 1,514 et 1,540, P−O liaison =1,579 A, P−O−P=156,8 o
The Kohmoto-Kadanoff-Tang renormalization-group method is extended to study the phonon properties of a class of one-dimensional quasiperiodic systems. Two models are employed, which correspond to the equation of motion for phonon problems with spring constants equal and two types of masses arranged successively in gen…
Photon-induced desorption (PID) and electron energy loss spectroscopy (EELS) applied to the system NO/O2/Pt(111) yield information on coadsorbate effects in surface photochemistry. A new NO species (denoted γNO) is observed in EELS [νγN−O=236 meV, ν(Pt−γNO)=49 meV], and is found to have a highly enhanced PID cross sec…
The pressure effect on the CDW formation and the superconductivity in NbSe 3 is investigated up to 18 kbar by resistive and diamagnetic measurements. Both the T 1 -CDW and the T 2 -CDW are suppressed under pressure, as reported earlier. The superconductivity appears at pressures above P c =7.5 kbar where the T 2 -CDW…
We study theoretically the interference effects and the resulting transmission of acoustic phonons in random superlattices, i.e., multilayered systems in which two kinds of building blocks A and B are stacked at random. We derive (i) the recursion relations satisfied by the superlattice structure factors, and (ii) an…
Condensation dynamics and structure of low temperature ≤100 K amorphous ices is studied using the classical trajectory simulation technique. Specifically, classical equations of motion are solved for a sequence of H2O molecules impinging at random on an initial nucleus of ten water molecules. The sticking probability…
The structure of alpha-D-glucose-NaCl is presented. C6H12O6.1/2(NaCl).0.39(H2O), Mr = 216.40, trigonal, P3(1)21, a = b = 9.721 (3), c = 17.06 (1) A, V = 1396 (1) A3, Dm = 1.54 (1), Dx = 1.54 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 2.859 cm-1, F(000) = 683.4, T = 293 K, final R = 0.044 for 744 reflections with I g…
Dependences of secondary electron emission of copper bombarded by an electron and an ion on the angle of incidence are investigated for the bombarding energies from 100 eV to 1 MeV, using a Monte Carlo simulation of the kinetic emission. The inverse cosine of the angle measured from the normal to the surface overestim…
Cristallisation dans C2/m avec a=11,663, b=3,6532, c=8,92 A, β=90,91, Z=4, affinement jusqu'a R=0,056. Les octaedres deformes de VO 6 sont lies et forment des couches de V 2 O 5 paralleles a (001). Les ions Na sont situes entres ces couches et entoures par sept atomes O