Materials Literature
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An MCSCF procedure is described which is based on the direct minimization of an approximate energy expression which is periodic and correct to second order in the changes in the orthonormal orbitals. Within this approximation, the CI coefficients are fully optimized, thereby accounting for the coupling between orbital…
Abstract The establishment of charge density waves (c.d.ws) in NbSe3 and the phenomena associated with their sliding are examined against the background of behaviour presented for a variety of other stranded transition metal chalcogenides. The work has been set in terms ofdiscom mensuration arrays, but with these not…
Abstract The results of a series of experiments demonstrate that solitons are the important excitations in trans-(CH)x and that the properties of these nonlinear excitations can be directly studied during photoexcitation or after doping. The importance of these concepts in the more general context of conducting polyme…
Abstract In contrast with intercalation compounds, which can exist both with and without organic molecules between the planes of inorganic material, ‘molecular composite’ compounds have organic groups covalently or ionically bound to inorganic layers. In such crystals the aim is to combine magnetic or optical properti…
Abstract Raman spectra of CxF1-δ(HF)δ(x/δ ≈ 12) show bands at 1600, 1355 and 839 cm-1, which are attributed to graphite-like vibrational modes of the carbon atom sheets. The infrared spectra show, in addition to graphite-like bands, absorptions at 1270 and 1100 cm-1, which are attributed to C-F stretching. Variable co…
Abstract The conductivity of certain organic polymers can be raised to metallic levels by chemical or electrochemical ߢp-doping’ (oxidation), or ‘n-doping’ (reduction). Polyacetylene, (CH)x, the prototype conducting polymer, has been studied more extensively than any other conducting polymer and the doping concepts in…
A new model of liquid-solid freezing, based on the orientational order in a three-dimensional liquid, is proposed. The novel aspect of the model is the inclusion of the coupling between the orientational and elastic degrees of freedom in a dense liquid. This allows for the explicit computation of several thermodynamic…
The application of the phenomenon of thermoluminescence to the measurement of absorbed radiation dose has progressed a great deal since the initial work by Daniels and colleagues referred to in chapter 1. Several thermoluminescent phosphors are now used routinely in many dosimetric applications. This chapter deals wit…
In order to explain ferrielectric behaviour, a phenomenological model given in terms of the polarisations of two non-equivalent sublattices is proposed. The free energy for a second-order phase transition is G= 1 / 2 f 1 P 1 2 + 1 / 2 f 2 P 2 2 +gP 1 P 2 + 1 / 4h(P 1 4 +P 2 4 ) (G>0, h>0), where f 1 -(T-T 1 )/C 1 and…
Molecular dynamics simulations of supercooled and glassy states of binary 'soft sphere' mixtures are reported. The transition to the amorphous solid phase appears to be smooth and takes place at a roughly concentration-independent value of an effective coupling parameter derived from a simple 'one-fluid' model.
In the h.c.p. structure three kinds of basal stacking faults can occur: two intrinsic faults (I1 and I2) and one extrinsic fault (E). In this study all three of them are observed and analysed by electron microscopy methods in pure Co. Special care is needed to distinguish I1 and I2 faults since several violations of t…
Aggregate centers in reactor irradiated single crystal α-Al2O3 are investigated using the thermochemical and photochemical methods. Isochronal and isothermal annealings of the bands at 302, 356, 450, and 570 nm are performed in detail to study the thermal stability and to obtain the activation energy (E) for the decay…
(Sc 0.35 Ti 0.65 )Fe 2 having the hexagonal Laves phase structure is a ferromagnet with the Curie temperature of 360 K. The ferromagnetic moment changes from 1.3 to 0.9 µ B around 70 K with increasing temperature. The transition is of the first order. The longitudinal stiffness constant for spin fluctuations changes a…
Filters which serve as dichroic beam dividers are useful for certain types of far-infrared photometer. We have used inductive cross metal mesh as reflective coatings on solid dielectric Fabry-Perot etalons to produce dichroic filters with quality factors in the range 3 < Q < 10. These filters reflect strongly at…
Studies of grain structure, size, distribution, and geometric arrangement are gaining importance especially from the point of view of thin-film interconnects for micron and submicron semiconductor technologies. We have studied the effect of annealing on the grain growth characteristics of pure Al films. As-deposited f…
The specific heats of liquid Se-Te alloys have been measured as a function of temperature. There have been large and maximum values in the specific heat curves of liquid Se 1- x Te x ( x =0.2, 0.3 and 0.4) alloys. They are explained in terms of Schottky-type specific heats due to the transition from non-metallic two-f…
The behavior of carbon atoms in relation to oxygen precipitation in Czochralski silicon crystals subjected to various heat treatments is investigated by means of infrared (IR) spectroscopy. It is shown that carbon atoms enhance and modify oxygen precipitation both at 750 and at 1000 °C. Perturbed [Oi−Ci] C(3) centers,…
We develop continuum elastic theories for the blue phases of cholesteric liquid crystals and for the metallic glasses. These theories are frustrated and possess ground states with networks of defect lines; the frustration can be relieved in a space of constant positive curvature (a sphere in four dimensions). The orde…
The electrical conductivity of the solid electrolyte \ensuremath{\alpha}-${\mathrm{Li}}_{2}$${\mathrm{SO}}_{4}$ is investigated for the temperature range 580--800 \ifmmode^\circ\else\textdegree\fi{}C and for pressures up to 0.6 GPa. The migration enthalpy at normal pressure is 0.45\ifmmode\pm\else\textpm\fi{}0.05 eV,…
Abstract The transverse relaxation rate of H 2 O in Al(H 2 O) has been measured as a function of temperature (255 to 417 K) and pressure (up to 220 MPa) using the 17 O‐NMR line‐broadening technique, in the presence of Mn(II) as a relaxation agent. At high temperatures the relaxation rate is governed by chemical exchan…