Materials Literature
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We present an ab initio study which identifies dominant effects leading to thermal conductivity reductions in carbon and boron-nitride nanotubes with isotope disorder. Our analysis reveals that, contrary to previous speculations, localization effects cannot be observed in the thermal conductivity measurements. Observa…
Luminescent silicon-rich nitride/silicon superlattice structures (SRN/Si-SLs) with different silicon concentrations were fabricated by direct magnetron cosputtering deposition. Rapid thermal annealing at 700 °C resulted in the nucleation of small amorphous Si clusters that emit at 800 nm under both optical and electri…
In this article, the synthesis of natural fiber-reinforced phenol-formaldehyde (PF) resin matrix-based polymer composites has been reported. Initially the phenol-formaldehyde resin was prepared by varying the concentration of formaldehyde with a fixed weight of phenol. Polymeric resins of different P:F ratios were sub…
Langevin simulations provide an effective way to study collective effects of Brownian particles immersed in a two-dimensional periodic potential. In this paper, we concentrate essentially on the behaviour of the tracer (DTr) and bulk (DB) diffusion coefficients as function of friction. Our simulations show that in the…
A high-quality organic thin film for integrated nonlinear optics is produced by molecular beam deposition of a compact molecule that has a high specific third-order polarizability. The resulting dense, homogenous, amorphous supramolecular assembly with a large third-order nonlinearity and high-optical quality enables…
We analyze the resonant inelastic x-ray scattering (RIXS) spectra at the $K$ edge of Mn in the antiferromagnetic insulating manganite ${\text{LaMnO}}_{3}$. We make use of the Keldysh-type Green's function formalism, in which the RIXS intensity is described by a product of an incident-photon-dependent factor and a dens…
Frustration of magnetic systems which is caused by competing interactions is the driving force of several unusual phenomena such as plateaus and jumps of the magnetization curve as well as of unusual energy spectra with for instance many singlet levels below the first triplet state. The antiferromagnetic cuboctahedron…
We investigated the electronic and magnetic properties of a series of zinc-blend II-V compounds by carrying out density-functional theory calculations including spin-orbit couplings. Contrary to the case of CaN and CaP, the half-metallic characteristics of the II-V compounds such as CaBi were found to be destroyed. Ou…
A recent experiment on the multiferroic BiMn$_2$O$_5$ compound under a strong applied magnetic field revealed a rich phase diagram driven by the coupling of magnetic and charge (dipolar) degrees of freedom. Based on the exchange-striction mechanism, we propose here a theoretical model with the intent to capture the in…
Using in situ synchrotron measurements of total reflection x-ray fluorescence, we find evidence of strontium surface segregation in (001)-oriented La0.7Sr0.3MnO3 thin films over a wide range of temperatures (25–900 °C) and oxygen partial pressures (pO2=0.15–150 Torr). The strontium surface concentration is observed to…
We study the chemisorption of CO molecule into sites of different coordination on (111) surfaces of late 4d and 5d transition metals. In an attempt to solve the well-known CO adsorption puzzle we have applied the relatively new vdW-DF theory of nonlocal correlation. The application of the vdW-DF functional in all cons…
Nowadays the state of the art Density Functional Theory (DFT) codes are based on local (LDA) or semilocal (GGA) energy functionals. Recently the theory of a truly nonlocal energy functional has been developed. It has been used mostly as a post DFT calculation approach, i.e. by applying the functional on the charge den…
Graphene field-effect transistors with Co contacts as source and drain electrodes show anomalous distorted transfer characteristics. The anomaly appears only in short-channel devices (shorter than approximately 3 μm) and originates from a contact-induced effect. Band alteration of a graphene channel by the contacts is…
It is the purpose of this short paper to show that the well known Griffiths theory of brittle fracture can be re-interpreted as a simple case of a modified Hamiltonian, and corresponds to a stationary action solution using the Euler-Lagrange equations. In this derivation it is still necessary to employ the equivalence…
White-LEDs are produced with the addition of a silicone-composite layer containing light-emitting converter material on top of a high-performance blue-LED chip. The color reproduction was significantly improved in comparison with commercially available white-LEDs.
Dynamic recrystallization (DRX) is almost universally observed in the microstructure of adiabatic shear bands. It is usually admitted that DRX results from the large temperatures that develop in the band along with very high local strains. This paper reports the observation of dynamically recrystallized nanograins in…
This work explores time-resolved emission imaging microscopy (TREM) for noninvasive imaging and mapping of live cells on a hitherto uncharted microsecond time scale. Simple robust molecules for this purpose have long been sought. We have developed highly emissive, synthetically versatile, and photostable platinum(II)…
Diatoms are single-celled algae that produce intricately structured cell walls made of nanopatterned silica (SiO(2)). The cell wall structure is a species-specific characteristic demonstrating that diatom silica morphogenesis is genetically encoded. Understanding the molecular mechanisms by which a single cell execute…
A huge enhancement of the superconducting transition temperature Tc was observed in a tetragonal FeSe superconductor under high pressure. The onset temperature was as high as 27K at 1.48GPa and the pressure coefficient showed an extremely high value of 9.1K∕GPa. The upper critical field Hc2 was estimated to be ∼72T at…
We report density functional calculations of the electronic structure, Fermi surface, phonon spectrum, magnetism, and electron-phonon coupling for the superconducting phase FeSe, as well as the related compounds FeS and FeTe. We find that the Fermi-surface structure of these compounds is very similar to that of the Fe…