Materials Literature
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A method for calculating the anisotropic elastic energy of a dislocation dipole in a periodic cell is derived in which the infinite image summation is absolutely convergent. The core energy of a screw dislocation in Si, extracted from atomistic simulation, is shown to be manifestly system size invariant. Existence of…
Enhanced surface reaction efficiency has been demonstrated in the photocatalysis of obliquely deposited TiO2 thin films with variously shaped columns such as zigzag, cylinder, and helix. The columnar thickness and spacing play an important role in the enhancement of the effective surface area, while the columnar shape…
We have designed high-efficiency finite-aperture diffractive optical elements (DOE's) with features on the order of or smaller than the wave-length of the incident illumination. The use of scalar diffraction theory is generally not considered valid for the design of DOE's with such features. However, we have found sev…
We present the observation of ferroelastoelectric switching in a ferroelectric material. It is achieved in barium titanate thin film by simultaneously applying electric field and compressive stress with the tip of a scanning force microscope. For low compressive stresses, the presented measurements reveal classical fe…
The Mo≡N bond is conjugated with the organic segment in the novel molecular organic-inorganic hybrid materials that have been obtained by Pd-catalyzed coupling of an iodo-functionalized hexamolybdate anion and an alkyne (see scheme; Ar=4-methylphenyl,3-5-di(tert-butyl)phenyl). The interaction between the polyoxometala…
Surface pattern formation in diblock copolymer films is investigated as a function of film thickness h and molecular mass M. Smooth films are observed for certain h ranges centered about multiples of the lamellar thickness L0, and we attribute this effect to an increase in the surface chain density with h in the outer…
Computer simulations of bubble oscillations are performed under conditions of sonoluminescence (SL) in water for various liquid temperatures. It is clarified that at almost all acoustic amplitudes, the bubble temperature at the collapse is higher in a colder liquid because a lesser amount of water vapor is trapped ins…
Current imaging scanning tunneling microscopy is used to observe the electronic wave functions in InAs/ZnSe core/shell nanocrystals. Images taken at a bias corresponding to the s conduction band state show that it is localized in the central core region, while images at higher bias probing the p state reveal that it e…
) shows induced circular dichroism, which is indicative of a chiral environment.
Extremely small colloidal InP quantum dots (QDs) with diameters ranging from 15 to 23 Å were synthesized, and the optical properties of close-packed arrays of these dots were studied. The isolated QDs in dilute colloidal solution exhibit pronounced discrete absorption spectra, indicating a narrow size distribution. Th…
We report results of numerical simulations of non isothermal dendritic flux penetration in type-II superconductors. We propose a generic mechanism of dynamic branching of a propagating hotspot of a flux flow/normal state triggered by a local heat pulse. The branching occurs when the flux hotspot reflects from inhomoge…
We show that an instability may be present in resonant tunneling through a quantum well in one, two and three dimensions, when the resonance lies near the emitter Fermi level. A simple semiclassical model which simulates the resonance and the projected density of states by a nonlinear conductor, the Coulomb barrier by…
Angle-resolved photoemission and scanning tunneling microscopy have been applied to study the intercalation of copper underneath a monolayer of graphite (MG) on Ni(111). The room-temperature deposition of copper on MG/Ni(111) in the coverage range 4--12 \AA{} leads to the growth of Cu islands on the MG. Annealing of t…
We report the low temperature properties of a new series of pyrochlore iridates R2Ir2O7 (R = rare-earth elements). We found that the compounds with R = Pr, Sm, Nd, and Eu exhibit metallic conductivity, whereas those with smaller rare-earth ions are nonmetallic. Such metal-nonmetal changeover is attributable to the imp…
We present a theoretical study of the interaction of vacancies with a tilt grain boundary in aluminum based on the density functional theory. The grain boundary volume expansion and vacancy induced contraction are calculated and compared for the nearest-neighbor atoms, and the former is found to be smaller than the la…
A new family of porous inorganic solids based on nanocrystalline metal oxides is discussed. These materials, made up of 4-7 nm MgO, CaO, Al2O3, ZnO, and others, exhibit unparalleled destructive adsorption properties for acid gases, polar organics, and even chemical/biological warfare agents. These unique sorption prop…
We show that the transition in AMnO3 from the orthorhombic perovskite phase to the hexagonal phase is promoted by inducing disorder on the A-site. The gap between the orthorhombic and the hexagonal phase is widened for disordered, mixed yttrium-gadolinium manganite samples. At the cost of the orthorhombic phase a two…
In this era of molecular biology, protein crystallization is often considered to be a necessary first step in obtaining structural information through X-ray diffraction analysis. In a different light, protein crystals can also be thought of as materials, whose chemical and physical properties make them broadly attract…
Theoretical work has so far focused on the role of host-element chemical potentials in determining defect formation energies that control doping levels in semiconductors. Here, we report on our analysis of the role of the dopant-impurity chemical potential, which depends on the source gas. We present first-principles…
The meso substituted Ni(II)(5,15-diNO 2 −octaethylporphyrin) coexists in at least three different conformers in CS 2 . To explore the structural properties of these conformers, we measured the resonance excitation profiles and depolarization ratio dispersions of various prominent Raman lines of Ni(5,15-diNO 2 −octaeth…