Materials Literature
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The critical properties of the Ising model on the Penrose lattice of a size up to 439,204 sites are studied by means of the Monte Carlo simulation. We make an analysis of a phenomenological Monte Carlo renormalization group based on finite-size scaling. The critical temperature T c and the magnetic critical exponent y…
Data on the internal pressure of hard-sphere and hard-disk fluids have been available for some time from computer simulations, even at densities above the freezing density. These results for the metastable fluids suggest that the pressure diverges at the density of random closest packing. However, our examinations of…
Electromagnetic waves can discriminate between objects of different handedness due to their transverse nature, which implies that the origin of chirality necessarily need not be molecular as in the case of optically active media. By embedding chiral microstructures in a host medium, effectively chiral composites can b…
We have investigated nonlinear characteristics of high-quality ${\mathrm{K}}_{0.3}$Mo${\mathrm{O}}_{3}$ single crystals in the temperature range of 30-100 K covering eight orders of magnitude in current and more than three decades in voltage. At some temperatures, high-field measurements were extended up to 1000 times…
Dynamics of an electron in quasiperiodic systems is studied numerically. Calculations are carried out for the one-dimensional tight-binding model with diagonal or off-diagonal modulation obeying the Fibonacci sequence. The width of the wavepacket of an electron put on a single site at time t =0 exhibits such an overal…
Modern density functional theory is used to study the freezing of a polydisperse liquid of hard spheres into both face centered cubic (fcc) and hexagonally close packed (hcp) crystals. Two physically relevant, continuous distributions of particle size are studied: the gamma (or Schulz) distribution and the Gaussian di…
We describe a lattice model of a supported monolayer of flexible amphiphile molecules which treats their full three-dimensional structure and includes nearest neighbor interactions between segments of the amphiphile chains, an attraction between the chain segments and the underlying substrate, and the inter- and intra…
A stochastic model is presented to predict the molecular weight dependence of the polymer fracture energy and strength for polymers with molecular weights higher than the critical value corresponding to the onset of entanglements. A chain scission criterion is invoked for the polymer chain segments crossing the fractu…
We report on investigations of one-dimensional thermal transport in compositionally modulated metal films produced with a systematic variation in atomic lattice mismatch. In the case of Ni-Cu, Ni-Mo, Ni-Ti, and Ni-Zr, we observe the relative effects of interfacial disorder on thermal diffusion. Our observations demons…
Experimental characterization of the bulk absorption properties of sapphire, spinel, yttria, and ALON as a function of temperature is accomplished using a Bomem DA3.02 vacuum Fourier transform spectrometer and a heated cell. The measurements are performed between 2 and 20 microm from room temperatures to 775 K. Spectr…
Infrared multiphoton dissociation (IRMPD) of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a molecular beam has been performed in order to investigate the mechanism of RDX thermal decomposition. A beam of molecules was crossed by a pulsed TEA CO2 laser and velocity distributions of the various products were measure…
Reflectance vs incidence angle measurements have been performed from 24 A to 1216 A on electron-beam evaporated samples of Ti, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au, and using a nonlinear least-squares curve-fitting technique, the optical constants have been determined. Independently measured v…
We analyze theoretically the oscillator strength and the third-order optical polarizability ${\ensuremath{\chi}}^{(3)}$ due to excitons in semiconductor microcrystallites. The nonlinear optical polarizability is shown to be greatly enhanced for an assembly of such microcrystallites as the exciton is quantized due to t…
The thermal properties of the 14 nonmagnetic cubic metals through the 4d transition series are derived from first-principles electronic-structure calculations coupled with a Debye treatment of the vibrating lattice. Debye temperatures and Gr\"uneisen constants are derived from an analysis of the compressional characte…
Using the electron-beam-induced barrier currents and the Monte Carlo simulation methods it was possible to determine the depth-dose function as well as the distribution function of the generation source for electron-hole pairs perpendicular to the injection direction. The depth-dose function was compared with results…
The properties of electrically conducting, semiconducting, and semi-insulating polymers are surveyed and their conduction mechanisms, mechanical properties, and suitability for space-based use and other advanced applications are evaluated.
Thermoluminescence emission spectra of six phosphors commonly used for TL dosimetry are presented at doses between 15 mGy and 1 Gy. The use of a Fourier transform spectrometer has made it possible to obtain spectra at doses considerably lower than those for spectra previously reported. The spectra are in the form of i…
Previous studies of the gas sensitivity of CuPC (copper phthalocyanine) and ZnPC have been extended to include CoPC and NiPC, with particular reference to ammonia detection. Ammonia sensitivity is found to depend on the crystal structure of the films, ammonia concentration and temperature. The alpha - beta phase trans…
The conductivity of four graphite powders was measured as a function of the volume fraction of graphite (or air) along (axial) and across (transverse) the direction of compression. The conductivity varies by between two and four orders of magnitude during these measurements. The results are shown to fit an equation wh…
Over recent years, Rolls-Royce plc has committed significant research resources to the development of diffusion bonding processes for the manufacture of existing and advanced titanium alloy aeroengine components and structures. Both aspects of the joining technique, i.e. 'solid-state ' and '…