Materials Literature
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We report measurements of the melting velocity of amorphous Si relative to that of (100) crystalline Si. These measurements permit the first severe experimental test of theories describing highly nonequilibrium freezing and melting. The results indicate that freezing in Si is inherently slower than melting; this asymm…
A new lattice model of polymer crystallization is described. Results of numerical solutions of rate equations for crystallization of a two-dimensional "crystal" are presented. It is shown that the crystal thickness varies inversely with supercooling and that kinetics similar to secondary nucleation occurs. This is tru…
We define a hopping Hamiltonian for independent electrons on a two-dimensional quasiperiodic Penrose lattice. This problem is then investigated numerically, up to systems of 3126 sites, and for various boundary conditions. We find the following results for the density of states: (1) There is a central peak of zero wid…
Neutron scattering experiments were carried out on the quasi-one-dimensional conductor (TaSe 4 ) 2 I. At the superlattice point (0.05, 0.05, 0.085) a soft temperature-dependent transverse acoustic (TA) mode polarised in the c plane was observed. A 'spoon-like' anomaly of the dispersion curve of the TA branch was obser…
XANES, X-ray photo-electron and optical spectra of divalent nickel in NiCr 2 O 4 and Ni 1-x Cu x Cr 2 O 4 compounds are reported. The characteristic parameters of the Ni(II) tetra -O chemical bond in spinels are not very sensitive to the Jahn-Teller effect. The tetragonal distortion c/a<1 for the Ni 1-x Cu x Cr 2 O 4…
The luminescence spectra and decay curves of Sb 3+ -doped Cs 2 NaMCl 6 (M=Sc,Y,La) are presented. In these compounds the 5s 2 ion is octahedrally surrounded by six chloride ions like the s 2 ions in alkali halides. Therefore, they can be considered as an ideal model system. It appears that the Sb 3+ luminescence in Cs…
Abstract When heated in air, minnesotaite begins to oxidise to a ferric form aI 400°C. By the onset ofdehydroxylation at 600°C, oxidation is virtually complete without significant changes in the lattice parameters.
Bend-contour pattern analysis is used to study processes occurring in initially dislocation-free selenium crystals during the formation of subgrain boundaries in the course of crystal growth. Using the data obtained on the magnitude and character of lattice disorientations in various types of emerging boundaries, a bl…
The general technology development and demonstration of a Nuclear Engine for Rocket Vehicle Application (NERVA), a joint AEC-NASA program, was undertaken successfully in the 1960's and terminated in 1971 for lack of a specific mission. Detailed flight engine specifications were defined and several candidate designs wh…
A new preparation method of Cu/Cu2O Schottky barrier solarcells is proposed and worked out. It combines resistive evaporation of a thin semitransparent copper electrode on a Cu2O substrate (step I) and exposition of the obtained junction to the H+ ion irradiation (step II). Both, dark and illuminated (AMI) current-vol…
Self-similar structures of single-crystalline domains in lipid monolayers at the air-water interface are observed after a stepwise increase of the surface pressure. It is shown that these fractal structures with Hausdorff dimensions of $d\ensuremath{\approx}1.5$ anneal because of the influence of edge tension on time…
This is the first of a series of papers in which a second-order perturbation theory is derived for the Hamiltonian of a metal hydride. The theory, which is called the fully harmonic lattice approximation, or FHLA, goes beyond the customary harmonic treatment of Horner and Wagner to include second-order terms for the h…
Nonresonant interband Faraday rotation in amorphous semiconductors, as a function of photon energy, may be described by an equation derived for direct transitions in crystalline semiconductors. In this paper it is shown how this equation may be obtained for the former case also, assuming a parabolic density of states…
Results of self-consistent first-principles calculations of the electronic band structures of the three cesium halides within the local-density functional formalism are presented. The calculations were done with the linear muffin-tin orbital (LMTO) method and relativistic effects were taken into account. The general f…
The steps in the interlayer spacing observed in annealing studies of artificial carbons on the one hand, and those seen in fast-neutron irradiation and grinding of graphite on the other hand, are shown to demonstrate the existence of interstitial carbon atoms between the aromatic planes of carbon atoms, $s{p}^{2}$ bon…
Dependences of electrical conductivity and ESR of iodine-doped polythiophene films, (C 4 H 2 SI y ) x , on iodine concentrations which are precisely determined by a neutron activation technique (from a dilute level of y ∼4×10 -4 to a deep level of y ∼4×10 -1 ) are reported. A drastic increase of conductivity from 10 -…
We show that the properties of many conducting polymers can be determined from the study of a simple, continuum, one-dimensional model with a limited number of relevant interaction parameters. Over most of the range of validity of the model, low-order perturbation theory in the electron-electron interactions is reliab…
A method of describing the nonlocality of exchange and correlation energy and potential, which gives the correct long-range imagelike behaviour, is adopted in a self-consistent calculation of a solid surface in the framework of the jellium model. The exchange-correlation potential V xc ( z ), within the approximation…
Transient-photocurrent measurements in glassy ${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ reveal an accurate power-law behavior spanning more than eight decades of time. In the multiple-trapping model this requires a density of valence-band-tail states varying exponentially with energy over almost five decades. The accurac…
Time-of-flight neutron diffraction data from a single crystal of K0.26WO 3 were refined with space group P63 using only l = 2n reflections (R(F) = 0.051 ). The odd-I data were not included in the refinement because of poor agreement with the structural model, indicating that the model is correct for a superposition of…