Materials Literature
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The magnetoresistance of graphite exhibits a sharp increase at a certain critical field ${H}_{c}$ (${H}_{c}\ensuremath{\ge}22$ T), where ${H}_{c}$ is sensitive to temperature. This anomaly was ascribed to the formation of an electronic charge density wave by Yoshioka and Fukuyama (YF). To obtain an expression of ${H}_…
The atomic structure of ${\mathrm{Si}}_{x}{\mathrm{S}}_{1\ensuremath{-}x}$ glasses is investigated by the use of Raman spectroscopy. The compositional dependence of the microstructures of these glasses can be conveniently divided into three regions. At Si${\mathrm{S}}_{2}$, the glassy structure is composed of randomly…
The near IR (overtone) spectra of water, H2O–D2O solutions, and a glass-forming glycerol +D2O solution have been measured in the temperature range 80 to −30 °C (−120 °C for the glycerol +D2O solution) using emulsion samples to gain access to the deep supercooling range. At −30 °C the intensity attributed to weakly hyd…
Square arrays of 20–35-nm-diam gold particles with 50-nm spacings were formed on thick sapphire substrates by electron beam lithography. After annealing at 125 °C the particles had an approximately circular projection on the substrate with a slightly smaller dimension in the perpendicular direction as inferred from sc…
The results of an extensive vibrational analysis of tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenafulvalene (TMTSF) and of their radical cations are presented. The polarized infrared absorption spectra of oriented crystalline samples of neutral TMTTF and TMTSF (4000–80 cm−1) are reported and compared…
L'isomere Z cristallise dans P2 1 avec Z=2; affinement jusqu'a R=0,063. L'isomere E cristallise dans P2 1 avec Z=2; afinnement jusqu'a R=0,48 (P) cristallise dans P2 1 /n avec Z=4; affinement jusqu'a R=0,073. Les isomeres E et Z cristallisent dans le groupe d'espace monoclinique chiral P2 1 . L'isomere E violet pâle s…
The well-known restrictions on the possible shapes of electron energy bands arising from one-dimensional (1D) periodic potentials do not apply to chainlike physical systems such as polymers or molecular stacks, which are three dimensional objects periodic along a line. For such quasi-one-dimensional (Q1D) crystals, ba…
We present a study of angle-resolved photoemission of the layered compound Ti${\mathrm{Te}}_{2}$. The results are compared to augmented-plane-wave band-structure calculations which predict Ti${\mathrm{Te}}_{2}$ to be a semimetal with an overlap of valence and conduction bands of 0.6 eV. Reasonable agreement with the c…
We have measured by ellipsometry the dielectric constant of pure and heavily doped $n$- and $p$- type silicon from 1.8 to 5.6 eV. Both ion-implanted laser-annealed and bulk doped samples were used with concordant results. A red shift of the ${E}_{1}$ and ${E}_{2}$ critical-point energies, together with a decrease in t…
High-resolution infrared spectroscopy of the Si(100)2 \ifmmode\times\else\texttimes\fi{} 1 surface upon water exposure shows that, in the temperature range investigated (80 to 500 K), the adsorption is dissociative. Molecular water can only be adsorbed at low temperatures on a surface with saturated dangling bonds.
The graphitic phases of C and Si are studied with the use of the pseudopotential local-density-functional approach. For graphite, good agreement with experiment is obtained for the in-plane lattice constant, interlayer spacing, isotropic bulk modulus, and graphite-diamond structural energy difference. Graphitic Si has…
The refractive indices of a commercially available specimen of single-crystal MgF2 were determined for both the ordinary and extraordinary rays at selected wavelengths from 0.2026 to 7.04 μm. Measurements were made by means of the minimum-deviation method on a precision spectrometer near 19°C. The experimentally deter…
The effect of charge-transfer doping on the geometric and electronic structures of conjugated polymers has been investigated at the ab initio level with explicit consideration of the doping agents. Three systems were chosen for study as prototypical examples of conjugated polymers with nondegenerate ground states: pol…
Selection of materials and expected magnetocaloric effects are discussed for magnetic cooling applications at elevated temperatures (400–800 K). Various considerations result in the selection of rare earth-transition metal compounds such as Sm2Fe17−xCox for this task. These materials offer a wide range of suitable mag…
Abstract As an introduction, the general thermodynamic treatments for binary cation exchange are reviewed. The normal choice of standard states for the cations in the clay phase, and commonly used thermodynamic formulations with different scales of measurement are both discussed. The definition of standard states for…
Abstract Kandites, smectites and vermiculites all form interlamellar inclusion complexes. A comparison has been made between sorption in zeolites, clay minerals and clathrates. In smectites and vermiculites sorption isotherms reflect in contour and behaviour three situations. Kandites show only the first of these, in…
Abstract The paper reviews the structures and crystal chemistry of clay minerals, including interstratified minerals and related phyllosilicates. Brief accounts are presented of the disordered structures encountered in the different mineral groups and a conceptual structural model for interstratified minerals is outli…
Abstract Three mechanisms for clay mineral formation (inheritance, neoformation, and transformation) operating in three geological environments (weathering, sedimentary, and diagenetic-hydrothermal) yield nine possibilities for die origin of clay minerals in nature. Several of these possibilities are discussed in term…
Abstract The physicochemical properties of smectite clay minerals that determine their industrial utilization are reviewed. Smectite is the name used for a group of phyllosilicate mineral species, the most important of which are montmorillonite, beidellite, nontronite, saponite and hectorite. These and several other l…
A theory of the magnetisation process in ferromagnets, based on existing ideas of domain rotation and domain wall motion is presented. This has been developed via a consideration of the various energy terms into a mathematical description of the process leading to an equation of state for a ferromagnet. The differenti…