Materials Literature
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Estimates of the indirect band gap for coherently strained alloys of ${\mathrm{Ge}}_{\mathrm{x}}$${\mathrm{Si}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$ on Si〈001〉 are given for x in the range 0\ensuremath{\le}x\ensuremath{\le}0.75. The present results were obtained by combining x-ray diffraction data with relevant defor…
Transparent conducting films of cadmium stannate (Cd2SnO4), zinc oxide, and aluminum-doped zinc oxide have been made by a simple, economical electroless deposition technique. The as-deposited films of cadmium stannate have a 75% transmittance in the visible, 48% reflectance in the IR, and a band gap of 2.7 eV. Its res…
LiZnN, like other Nowotny-Juza filled tetrahedral ${A}^{\mathrm{I}{B}^{\mathrm{II}{C}^{\mathrm{V}}}}$ compounds, consists of a ${B}^{\mathrm{II}{C}^{\mathrm{V}}}$ zinc-blende lattice with the ${A}^{\mathrm{I}}$ atoms filling half of the available tetrahedral interstitial sites. Using band calculations we deduce an ``i…
A method for the vitrification of pure liquid water and dilute aqueous solutions is described which is the only one without a liquid cryomedium for heat transfer: rapid cooling of aqueous aerosol droplets on a solid cryoplate. This method is not limited to water and aqueous solutions, but can be used for the vitrifica…
The nucleation of persistent slip bands in stressed materials is described as a cooperative phenomenon for dislocation populations. It is the competition between their mobility and their nonlinear interactions (creation, annihilation, and pinning) which causes the instability of uniform dislocation distributions versu…
We present a theory of the first-order transition to the metallic state in polyacetylene in terms of a crossover from a lattice of charged solitons to a regular array of polaronlike distortions. The polaronic metal is shown to have a strong indirect attractive interaction, ${\mathrm{U}}^{\mathrm{*}}$\ensuremath{\simeq…
The Raman scattering from various model structures for amorphous silicon is computed. It is shown that the width of the ``optic peak'' increases roughly linearly with the rms bond-angle distortion \ensuremath{\Delta}${\ensuremath{\theta}}_{b}$ of the network. The experimentally observed linewidths lead to 7.7\ifmmode^…
The Raman spectrum of PbHPO 4 has been studied as a function of temperature between 10 and 320K (T c approximately=310K). A soft-mode is observed whose frequency has a temperature dependence that is close to, but not the same as, the spontaneous polarisation which follows the proton ordering. Several of the Raman line…
The authors argue that many phenomena associated with metal/nonmetal interfaces and similar situations with a large dielectric constant mismatch can be understood in terms of the image interactions due to charges in the nonmetal. The effects are additional to the traditional interactions, and are especially significan…
Debye relaxation behaviour is unique in the sense that all memory of excitation is instantaneously lost. It is shown that the presence of higher-frequency relaxations for components of the same dipole degrades this property by extending the memory into the timescale of relaxation, thus giving a nonDebye behaviour whic…
Bisphthalonitrile monomers were cured neat, with nucleophilic and redox co-reactants, or in combination with a reactive diluent. Dynamic mechanical measurements on the resulting polymers from -150 to +300°C turn up several differences attributable to differences in network structure. Rheovibron results were supplement…
A Comment on the Letter by D. G. Pettifor and R. Podloucky, Phys. Rev. Lett. 53, 1080 (1984).Received 23 January 1985DOI:https://doi.org/10.1103/PhysRevLett.55.260©1985 American Physical Society
A nonlinear theory of domain walls in intercalation compunds is presented. Realistic domain-wall energies and barriers to the relative motion of intercalate domains are calculated for the entire range of guest species intercalating into graphite. The different stackings of host layers found in stage-2 compounds are st…
A theory is developed for the hcp-fcc structural phase transition in close-packed metals as a function of the average electron concentration per atom. It is found that the transition can be continuous at low temperatures. Ordered polytypic stacking sequences are found near the transition point. Short-period structures…
We study the relaxation of thermally excited orientation fluctuations in a polymer nematic liquid crystal using photon correlation spectroscopy. The material studied is poly-\ensuremath{\gamma}-benzyl glutamate at a concentration just above the isotropic to nematic transition point. The relaxation rates of elastic def…
The mechanism of GTP-specific activation of the membrane-bound cellulose synthase system of Acetobacter xylinum has been further elucidated. The supernatant fraction derived from washed membranes of this organism contains an enzyme which reacts with GTP to form a low molecular mass, heat-stable compound,tentatively ch…
We describe a system where the dynamics of reversible clustering, ordering, and growth in two dimensions can be directly observed. The system consists of uniform colloidal particles trapped at an air/water interface. We attribute the attraction between particles mainly to pairwise potential with a longer-range van der…
Recent discoveries of new magnetic materials may greatly improve the performance of devices containing such materials and may lead to entirely new applications. For example, boron-based temary compounds for permanent magnets make new compact motor designs practical; amorphous transformer materials show greatly reduced…
Abstract Two constitutive models for the simulation of fracture and fragmentation processes in rapidly loaded rocks are studied. The models were included in a wave propagation finite element code. The results obtained from the two models were compared by a study of the intensity and extent of fracturing obtained from…
A molecular-level analysis that explains the differences in crazing behaviour encountered in polymeric glasses is presented. Considering the separation of molecules or segments of them as the controlling mechanism for crazing (at the initiation stage), it is found that in vinyl polymers such as polystyrene and polymet…