Materials Literature
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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
It is shown that in the nonretarded regime, the frequency of the long-wavelength surface plasmon of a free-electron metal is directly related to the overlap of the metal's unperturbed electron density and the normalized, fluctuating potential of the surface plasmon. This result directly expresses the idea that the sur…
We present results for the temperature dependence of electrical conductivity for amorphous ${\mathrm{V}}_{\mathit{x}}$${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$ alloys. The alloys investigated span the composition range from x=0.5 to 0.1. For the alloys with more than 20 at. % V, the temperature dependence c…
We have measured the oxygen-nickel distance in Ni(111)-p(2\ifmmode\times\else\texttimes\fi{}2)O using the electron-energy-loss fine-structure technique. Using the phase shift obtained on a heavily oxidized sample, we obtained 1.94\ifmmode\pm\else\textpm\fi{}0.05 \AA{}. This value is in slight disagreement with that ob…
2C 8 H 12 N + •CuCl 4 2− (I) cristallise dans P cab avec a=7,328, b=7,295, c=36,618 A, Z=4, affinement jusqu'a R=0,068. 2C 8 H 12 N + •CuBr 4 2− cristallise dans P cab avec a=7,654, b=7,756, c=38,042 A, Z=4, affinement jusqu'a R=0,067. Chaque ion de cuivre forme quatre liaisons Cu-X (X=Cl − , Br − ) dans un arrangemen…
X-ray photoemission and synchrotron-radiation photoemission were used to study the reaction of metals and molecular oxygen at low temperatures. Combined core-level and valence-band measurements permit the identification of various oxygen species. When Li, Cs, K, and La are deposited on solid oxygen, an O 1s feature ne…
We develop a model to explain the universal low-temperature properties of glasses in the 1T10 K temperature range. Our model consists of elastic dipole ``defects'' which are placed randomly in an elastic continuum. We derive a Hamiltonian for defects interacting via their long-range strain fields. We simulate a system…