Materials Literature
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Strong photoluminescence (PL) is observed in nanostructured crystalline tungsten oxide thin films that are prepared by thermal evaporation. Two kinds of films are investigated—one made of nanoparticles and another of nanowires. At room temperature, strong PL emissions at ultraviolet-visible and blue regions are found…
We study the pressure dependence of the melting mechanism of a surface free Lennard-Jones crystal by constant pressure Monte Carlo simulation. The difference between the overheating temperature($T_{OH}$) and the thermodynamical melting point($T_M$) increase for increasing pressure. When particles move into the repulsi…
A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponent t, in disagreement with the standard theory of percolation which predicts t = 2.0 for all three dimensional systems. Various models have been proposed in…
The structure and polarization of the as-yet hypothetical Ruddlesden--Popper compound ${\mathrm{Pb}}_{2}\mathrm{Ti}{\mathrm{O}}_{4}$ are investigated within density-functional theory. Zone center phonons of the high-symmetry ${\mathrm{K}}_{2}\mathrm{Ni}{\mathrm{F}}_{4}$-type reference structure, space group I4/mmm, we…
We show that a diatomic dot molecule made of two identical, vertically stacked, strained InAs/GaAs self-assembled dots exhibits an asymmetry in its single-particle and may-particle wavefunctions. The single-particle wave function is asymmetric due to the inhomogeneous strain, while the asymmetry of the many-particle w…
Transmission electron microscopy studies of [100], [110], and [111] oriented $\mathrm{Fe}{\mathrm{Cr}}_{2}{\mathrm{S}}_{4}$ single crystals at different temperatures reveal a structural transition at low temperatures indicating a cubic-to-triclinic symmetry reduction within crystallographic domains. The overall crysta…
We study the mechanical and conformational properties of networks of helical polymers with a combination of Monte Carlo simulations based on the Wang-Landau algorithm and the Three-chain Model. We find that the stress-strain behavior of these networks has novel features not observed in typical networks made of synthet…
The electronic structure and selected zone-center phonons in Yb graphite intercalation compound (YbC6) are investigated {theoretically} using density functional calculations and LDA+U approximation for Coulomb correlations in the f shell, and experimentally using angle-resolved photoemission. We find that both in LDA…
We report on the temperature dependence of the mobility, $μ$, of the two-dimensional electron gas in a variable density AlGaN/GaN field effect transistor, with carrier densities ranging from 0.4$\times10^{12}$ cm$^{-2}$ to 3.0$\times10^{12}$ cm$^{-2}$ and a peak mobility of 80,000 cm$^{2}$/Vs. Between 20 K and 50 K we…
Today, most application of time-dependent density functional theory (TDDFT) use adiabatic exchange-correlation (XC) potentials that do not take into account non-local temporal effects. Incorporating such "memory" terms into XC potentials is complicated by the constraint that the derived force and torque densities must…
Electronic states in nanographite ribbons with zigzag edges are studied using the extended Hubbard model with nearest neighbor Coulomb interactions. The nearest Coulomb interactions stabilize electronic states with the opposite electric charges separated and localized along both edges. Such states are analogous as nan…
We report a high-resolution experimental detection of the resonant behavior of magnetic vortices confined in small disk-shaped ferromagnetic dots. The samples are magnetically soft Fe-Ni disks of diameter 1.1 and 2.2 um, and thickness 20 and 40 nm patterned via electron beam lithography onto microwave co-planar wavegu…
By means of quasielastic neutron scattering, we have studied the hydrogen dynamics in glassy polyethersulfone, revealing the phenylene ring motions. The combination of a time-of-flight (TOF) and a backscattering spectrometer has allowed us to cover the microscopic and mesoscopic time scales (∼10 -13 −10 -9 s) in a mom…
Palladium clusters have been synthesized by the "ship-in-a-bottle" approach in the supercages of NaX and NaY faujasite zeolites. In comparison with CO adsorbed on a bulk Pd electrode, the same molecule adsorbed on the Pd clusters electrodes evoked an enhanced IR absorption (EIRA). The enhancement factors have been det…
It is well-known that a bulk, symmetric, A-b-B diblock copolymer forms a lamellar morphology, with period L, below an order-disorder transition (T(ODT)) temperature, for chiN < 10.5; chi is the Flory-Huggins interaction parameter and N is the degree of polymerization of the copolymer. The ordering temperatures of poly…
The molecular architecture of dendronized polymers can be tuned to obtain nanoscale objects with desired properties. In this paper, we bring together experiments and computer simulations to study the thermodynamic and dynamic properties of a single dendronized polymer chain. We find that, upon changing certain archite…
Electronic absorption spectra, fluorescence emission spectra, ATR-FTIR spectra, cyclic voltammetric measurements, and ab initio quantum calculation are used to study the properties of morin in SDS micelles of different microstructures and microenvironments and to gain the information about the binding of morin with th…
Two boron nitride (BN) nanostructures, the bamboo-like nanotubes and nanothorns where the nanosize h-BN layers are randomly stacked looking like thorns, were synthesized selectively via thermal chemical vapor deposition of B/B(2)O(3) under the NH(3) flow at 1200 degrees C. Electron energy-loss spectroscopy reveals the…
We introduce a novel pattern matching algorithm optimized for X-ray powder diffraction (XRPD) data and useful for data from other types of analytical techniques (e.g., Raman, IR). The algorithm is based on hierarchical clustering with a similarity metric that compares peak positions using the full peak profile. It inc…
The epoxidation of styrene catalyzed by a reaction-controlled phase transfer catalyst [(C 18 H 37 (30%)+C 16 H 33 (70%))N(CH 3 ) 3 ] 3 [PW 4 O 16 ] with H 2 O 2 in a biphasic medium was investigated. Under certain conditions, the selectivity for styrene oxide was 95%, the conversion of styrene based on H 2 O 2 was 85%…