Materials Literature
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We have performed ab initio calculations of the crystal structure and electronic structure of ${\mathrm{B}}_{6}$O using an expansion in over 11 700 plane waves. The crystal structure is compared with recent x-ray data; contour plots show the two oxygen atoms in the unit cell do not bond to each other, and the heat of…
Low-frequency Raman scattering of amorphous polymers [polyethyleneterephthalate (PET) and polymethylmethacrylate] is investigated. The low-frequency Raman band called ‘‘Boson peak’’ is interpreted in terms of a noncontinuous structure, similar to that of inorganic glasses, i.e., solid amorphous polymers are composed o…
We study the aggregation kinetics of Electro-Rheological Fluid particles which interact through dipoles induced by an external electric field and experience negligible thermal motion. For a system in d-dimensions, our theoretical calculations show that the average cluster size s av increases with time t as s av ∝ t d…
Single-crystal alloys of diamond with Si and Ge are investigated theoretically. An indirect band gap Γv25′ → Δc1 is found for the new semiconductor Si1−x−yGexCy over most compositions x and y, with an indirect Γv25′ → Lc1 gap found for the remaining compositions. The estimated band gaps span the 0.62–5.5-eV-range. Pre…
The dielectric permittivity and loss of vapor-deposited amorphous solid water (ASW) have been measured for fixed frequencies of 1 and 10 kHz from 80 K to its crystallization temperature. Similar measurements have also been made on the cubic ice formed after the crystallization of ASW and the hexagonal ice formed on he…
Second harmonic generation (SHG) has been studied in lithium diborate (Li 2 B 4 O 7 ) single crystal from room temperature up to the melting temperature. The magnitudes of the SHG coefficients d 33 and d 31 , at room temperature are, respectively, 3.1 and 0.4 relative to d 11 of quartz. The decrease of the SHG signal…
The embedded-atom method is used to calculate the surface stresses and the interface stresses for several fcc metals and interfaces between them. While the surface stresses are all positive (i.e., they tend to put the underlying crystal in compression), in several instances (e.g., in the Pt/Ni system) negative interfa…
Perturbation formulas are derived for calculating the vibrational dynamic polarizability (αv) and hyperpolarizabilities (βv and γv ) of polyatomic molecules. These formulas, based on an initial harmonic oscillator approximation, include corrections for mechanical anharmonicity (cubic) terms in the vibrational potentia…
We have performed angle-resolved-photoemission experiments and local-density-functional (LDA) band calculations on NiO to study correlation and band effects of this conceptually important compound. Our experimental result suggests a dual nature of the electronic structure of NiO. On the one hand, the LDA band calculat…
Domain wall contributions to the dielectric, piezoelectric, and elastic properties of tetragonal ferroelectric ceramics, as discussed extensively in the past, are calculated. A simple model shows that the motion of 90° domain walls causes a shear deformation and an approximately homogeneous electric field in the grain…
The full-potential linear-muffin-tin-orbital method in combination with the local-density-functional theory is used to calculate the equilibrium lattice constant, the cohesive energy, the bulk modulus and its pressure derivative, the elastic constants, the Kleinman internal displacement parameter \ensuremath{\zeta} th…
A valence-force-field model has been used to study the lattice dynamics of molybdenum disulfide single molecular layers. A comparison between the room-temperature Raman spectra of aqueous suspensions and the calculated phonon-dispersion curves for single layers of ${\mathrm{MoS}}_{2}$ with trigonal prism and octahedra…
Absolute total cross sections for scattering of electrons by water molecules measured in the 4-20 eV incident energy range using a linear electron transmission device are presented. The results are compared with previous data.
The flow stress of many metals is known to vary more strongly with strain rate epsilon above a critical value epsilon c than below it. An analysis of previous authors' measurements on copper indicates that the value of epsilon c varies systematically with specimen size. An estimate of inertial stress shows that inerti…
Total electron scattering cross sections for C 2 H 4 , C 2 H 6 , C 3 H 6 (propene and cyclopropane) and C 3 H 8 have been measured in the energy range between 4 and 500 eV. Measured results show a remarkable isomer effect and dependence on the geometrical dimension of the molecule.
The locally restricted motion of hydrogen and deuterium which are trapped at Cd acceptors in silicon has been studied by perturbed-angular-correlation spectroscopy. Close Cd-H and Cd-D pairs were identified by their characteristic electric-field gradients. The kinetics of these complexes was extracted directly from th…
Preparation of semiconducting vanadium silicate glasses by the sol-gel route and the results of electrical measurements are reported for the first time. The temperature dependence of the electrical conductivity has been analyzed in terms of small polaron as well as percolation models.
High resolution neutron scattering studies of vibrational spectra (2-800 meV) were carried out on the in -, delta ' and delta -phases of titanium hydride, obtained after high pressure treatment. The observed splitting of the fundamental optic peak in the delta -phase spectrum can be explained by a strong H-H interacti…
Porous silicon membranes have been formed by electrochemical etching through wafers up to 500 μm in thickness. The results show that there is essentially no limit to the thickness of porous silicon layers and that self-supporting porous structures can be formed by this method. In addition, the membranes are structural…
Binary SmFe12 and Sm(Fe,T)12 films, where T =Ti and V, crystallized into the ThMn12-type structure, have been synthesized as sputtered films such that the c axes of the crystallites are oriented perpendicular to the film plane. It has been possible to synthesize Sm(Fe,T)12 films which exhibit a very dominant (002) tex…