Materials Literature
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The relationship between the ion-beam energy and the stress in thin carbon films is studied using two-dimensional molecular-dynamics simulations. In agreement with experiment, a transition is seen from tensile to compressive stress with increasing ion energy. The compressive stress reaches a maximum near 30 eV, after…
We have analysed the expression of five protein kinase C [PKC] isoforms in an in vitro model using nontumorigenic rat colonic epithelial cells FRC/TEX CL D [D/WT] and in the related tumorigenic Ha-ras-transformed FRC/TEX CL D/H-ras line [D/ras]. The PKC subspecies alpha, delta, epsilon and xi were expressed at the pro…
We have developed, in the framework of a broken-bond model, a method to determine the surface composition of transition metal alloys. The model is based on the equivalent-medium approximation which allows us to calculate the energies of surface layers as a function of local concentration. The model also considers bond…
Trimanganese(II) dipotassium bis(hydroxide) bis(tetraoxovanadate), K2Mn3(OH)2(VO4)2, has a layered structure. The [Mn3(OH)2(VO4)2]n2n- layers comprise CdI2-like planes of MnO4(OH)2 octahedra with 1/4 Mn vacancies, to which VO4 tetrahedra are linked on both sides via three vertices; the fourth vertex points into the in…
A general scheme for the spin adaptation of open-shell coupled-cluster theory is presented, and the generalization to genuine multireference cases is briefly discussed. In our formulation the wave operator is parameterized such that it automatically commutes with the spin operators, and the correlated wave function is…
We describe by approximate MO calculation a number of species for which high spin states are either the ground state or lie very low in energy. These are models for the spin coupling in projected ferromagnetic organic materials. The theory guiding their construction is based on planar conjugated systems, while experim…
A range of $〈110〉$ symmetric tilt grain boundaries (GB's) are investigated in several fcc metals with simulations and high-resolution electron microscopy. Boundaries with tilt angles between 50.5\ifmmode^\circ\else\textdegree\fi{} and 109.5\ifmmode^\circ\else\textdegree\fi{} dissociate into two boundaries 0.6 to 1.1 n…
The results of first-principles calculations of the electronic band structures, equilibrium lattice constants, cohesive energies, bulk moduli, and magnetic moments are presented for the rare-earth pnictides with the rocksalt structure and chemical formula R-V, where R=Gd, Er, and the group-V elements N, P, and As. The…
In the context of perovskite quantum paraelectrics, we study the effects of a quadrupolar interaction $J_q$, in addition to the standard dipolar one $J_d$. We concentrate here on the nonlinear dielectric response $χ_{P}^{(3)}$, as the main response function sensitive to quadrupolar (in our case antiquadrupolar) intera…
Motivated by the negative thermal expansion observed for silicon between 20 K and 120 K, we present an ab initio study of the volume dependence of interatomic force constants, phonon frequencies of transverse-acoustic TA(X) and TA(L) modes, and of the associated mode Gr\"uneisen parameters. The influence of successive…
Using first-principles total-energy pseudopotential calculations, we have studied the properties of chains of potassium and aluminum in nanotubes. For BN tubes, there is little interaction between the metal chains and the tubes, and the conductivity of these tubes is through carriers located at the inner part of the t…
Electronic states of carbon nanotubes in a magnetic field perpendicular to the axis are studied in a tight-binding model and the validity of k · p theory is examined. The energy bands near the Fermi level calculated in the tight-binding model agree with those of k · p in a wide magnetic-field range except in extremely…
In this work the relationship between the characteristic energy of the Urbach edge ${E}_{0}$ and the parameter ${B}^{\frac{1}{2}}$ of the Tauc's representation of the absorption coefficient of $a$-SiN- and $a$-GeN-based alloys is presented and discussed. No correspondence has been experimentally found between ${B}^{\f…
We present a unified theoretical approach to electromagnetic plane waves reflected or transmitted at arbitrarily anisotropic and homogeneous layered systems. Analytic expressions for the eigenvalues for the four-wave components inside a randomly oriented anisotropic medium are reported explicitly. As well, the partial…
We have operated a supertip-type field emitter to provide electron beams of low angular divergence and high intensity. The beams obtained from a supertip on a W tip are characterized by narrow emission angles of , effective emission areas of and energy spreads of eV (FWHM) at stable total emission currents of nA. The…
Poly(dimethylsiloxane) (PDMS) and aromatic polyamide (aramid) multiblock copolymers (PASs) ranging from 26 wt % to 75 wt% in PDMS content were prepared and cast into transparent, ductile, and elastomeric films from N,N′-dimethylacetamide solutions. The gas permeation properties and dynamic thermomechanical properties…
Disiloxane–aromatic polyamide(aramid) multiblock copolymers(2SiPASs) were synthesized using 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane(BATS) as an analog of aramidsilicone resin consisting of aromatic polyamide and poly(dimethylsiloxane) (PDMS). 2SiPASs afford a transparent and toughened plastic film. The su…
Real ferroelectric capacitors are usually asymmetric. In this paper, the current - voltage characteristic of asymmetric Pt/Pb(Zr,Ti) /Pt (Pt/PZT/Pt) thin film capacitors is studied quantitatively by using an asymmetric totally depleted back-to-back Schottky model as well as by experiment. The model successfully descri…
Surface morphology of asymmetric and homogeneous membranes prepared from poly(phenylene oxide) (PPO) was studied by tapping mode atomic force microscopy (TMAFM). As expected, a significant difference in the morphology between the top and the bottom surfaces of the asymmetric membrane was observed. The images of the to…
Reflection high energy electron diffraction (RHEED) intensity measurements reveal that the strain in a Si1-xGex layer on a vicinal Si(001) surface converts a (1 X 2) domain dominated step configuration to a (2X1) domain dominated one. The dependence of the effect on the Ge content is similar to the dependence of the c…