Materials Literature
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An attempt is made to explain the first-order phase transition (180.4 degrees C) and the presence of an intermediate phase (180.4 degrees C-300 degrees C) between the para- and ferro-phases in lead phosphate, Pb 3 (PO 4 ) 2 , by invoking the basic ideas of the three-dimensional renormalised Potts model. This involves…
Ferroelectric domain walls have recently been considered as candidates for the occurrence of non-linear (soliton) excitations and roughening transitions. By means of X-ray or neutron scattering experiments, the domain walls may be observed directly and their width may be measured. The occurrence of a roughening transi…
Differential elastic scattering of electrons at 7.5, 10, 12.5, 15, 17.5 and 20 eV from neon is reported. The s, p, d and f phaseshifts derived from the measured cross sections are also presented.
The frequency ($f$) and temperature ($T$) dependent conductivity ($\ensuremath{\sigma}$) is reported for cis-${(\mathrm{CH})}_{x}$, trans-${(\mathrm{CH})}_{x}$, and ammonia-compensated ${(\mathrm{CH})}_{x}$. A strongly $T$-dependent dc $\ensuremath{\sigma}$ together with a weakly $T$-dependent ac $\ensuremath{\sigma}$…
The origin and nature of the two split-off conduction bands in V 2 O 5 is studied by means of a decoupled effective tight-binding Hamiltonian for the conduction band. This method is first shown to give reliable results, provided all interactions are taken into account and a first-order correction for the energy depend…
The authors present results of a dynamical simulation of UO 2 at high temperatures. The calculations confirm the occurrence of superionic oxygen conduction, but find that the level of disorder on the anion superlattice is low. The results, however, suggest there are exceptionally large, anisotropic thermal parameters…
Abstract Recent advances in microscope techniques have been used in a reinvestigation of the kinetics of the formation and the growth of nuclei developed during dehydration of cleaved (111) faces of relatively perfect crystals of the alums KAl(SO4)2. 12H2O and KCr(SO4)2. 12H2O , and solid solutions of five intermediat…
Two structural phase transitions in (CH3NH3)2, ZnCI4 at 426 and 484 K are discovered and investigated by X-ray diffraction, calorimetric, dielectric, thermal expansion, and optical measurements. The crystals are shown to be ferroelastic below 426 K. This behaviour is explained by a symmetry change Pnma-P21/a, which is…
Monophasic magnesium-nickel ferrites with varying amounts of magnesium and nickel are prepared and subjected to different heat treatments. The cation distribution in these compounds is calculated from magnetisation values assuming a collinear spin arrangement. The amount of Mg2+ on the A sites in magnesium rich compou…
In the temperature range from 848 to 1169 K chemical diffusion coefficients of Zn in α-Fe are given for Zn concentrations between 0 and 12 at%. Above 1068 K the tracer diffusion coefficient (nzn → 0) can be described by an Arrhenius law with D0 = 60 cm2 s−1 and Q = 262.6 kJ mole−1. For lower temperatures the diffusion…
The phase transition of NaNO2, is investigated by using X-ray powder diffractometry. The temperature dependence of the lattice constants, peak intensities, and the order parameter of the ferroelectric phase, in the range of 27 to 200 °C, show the same results as obtained by using single-crystal diffractometry. These e…
The properties of regions swept by a moving dislocation in silicon crystals are experimentally studied. The peculiarities of forming traces of various types behind dislocations observed by electron microscopy and chemical etching are investigated. These traces are found to arise as result of point defect redistributio…
The systematics of the onset of deformation in the $N=88\ensuremath{-}90$ region is reexamined in light of the recently discovered shell closure at $Z=64$. It is shown that the microscopic explanation of the origin of deformation already proposed for the $A\ensuremath{\sim}100$ region is equally applicable here and le…
Polyacetylene (CH)z is a simple conjugated polymeric system, the electrical behaviour of which is considerably modified by doping processes: from an insulating behaviour it successively becomes semi-conducting and even metallic. In this work first the dopant profiles through the sample is measured and the macroscopic…
An electron trap which strongly affects the photoconductivity of colored $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ has been investigated from 10 to 300 K. The trap, which also causes the 260-K thermoluminescence peak and makes possible the interconversion of $F$ and ${F}^{+}$ centers by opti…
Photodissociation of XeF2 with synchrotron light pulses (0.3 ns duration) has been used as the source of the XeF(B, C, and D) excited states. The time-resolved profiles of the intensity of the resulting fluorescence have been recorded and partially analyzed. Most of the measurements were made in the strong XeF2 absorp…
The solid–vapor equilibrium line and the liquid–vapor equilibrium line near the melting region for classical two-dimensional systems of particles interacting by Lennard-Jones (12,6) pair potentials are determined from Monte Carlo simulations with 224 particles. Structural and thermodynamic properties are evaluated for…
A general formula is derived for the electron occupation numbers appropriate for multicharge centers in semiconductors, including excited states. The results are used to rederive and generalize several formulas of interest in the literature, in order to show exactly how the degeneracies of individual states enter in.…
A theoretical study of the electronic structure of amorphous $\mathrm{Si}{\mathrm{O}}_{x}$ is performed. The calculation is done using a realistic tight-binding Hamiltonian for a cluster-Bethe-lattice model. Results of the calculations are in good agreement with optical-absorption measurements for the entire range of…
The quantum statistical mechanics of a polarizable fluid model is considered using a path-integral approach. The quantum mechanical partition function associated with the internal degrees of freedom of each molecule is approximated by a classical partition function of a polymer ring, while the center-of-mass motion of…