Materials Literature
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Measurements of polarization-dependent soft x-ray absorption reveal that the electronic states determining the low-energy excitations of NaxCoO2 have predominantly a(1g) symmetry with significant O 2p character. In contrast to the prediction of band theory, doping-dependent O 1s x-ray absorption shows a large transfer…
Following our previous works on pure-silica-zeolite (PSZ) MFI, in this study we explore PSZ MEL as a new option for low-k dielectric films. Our motivation has been to increase the microporosity of the spin-on films by moving to structures with a framework density (FD) lower than MFI. Nanoparticle PSZ MEL suspensions w…
We show, computationally, that single-walled silicon nanotubes (SiNTs) can adopt a number of distorted tubular structures, representing respective local energy minima, depending on the theory used and the initial models adopted. In particular, "gearlike" structures containing alternating sp(3)-like and sp(2)-like sili…
In our recent studies (Vinh-Thang, H.; Huang, Q.; Eic, M.; Trong-On, D.; Kaliaguine, S. Langmuir 2005, 21, 2051-2057; Vinh-Thang, H.; Huang, Q.; Eic, M.; Trong-On, D.; Kaliaguine, S. Stud. Surf. Sci. Catal. 2005, in press), a series of synthesized SBA-15 materials were characterized using nitrogen adsorption/desorptio…
A mesoscopic model is developed for static and dynamic simulations of nanomechanics of carbon nanotubes (CNTs). The model is based on a coarse-grained representation of CNTs as ``breathing flexible cylinders'' consisting of a variable number of segments. Internal interactions within a CNT are described by a mesoscopic…
BaMgAl 10 O 17:Mn phosphor particles with a spherical shape and fine size of less than 1 μm were prepared by spray pyrolysis, and their luminescence properties under vacuum ultraviolet (VUV) excitation were investigated by changing the concentration of activators and the composition of host matrix. It was found that b…
A Rietveld method is described which extracts information on crystal structure, texture and microstructure directly from two-dimensional synchrotron diffraction images. This is advantageous over conventional texture analysis that relies on individual diffraction peaks, particularly for low-symmetry materials with many…
Interest in radiation damage is growing rapidly owing to the surge in macromolecular crystallography experiments carried out at modern brilliant synchrotron macromolecular crystallography beamlines. Work on the characterization of radiation damage in cryocooled protein crystals is starting to have some impact on our u…
The Troika II beamline at the European Synchrotron Radiation Facility was conceived as a versatile beamline for the study of liquid and solid interfaces, combining grazing-incidence diffraction, X-ray reflectivity and grazing-incidence small-angle scattering in a single instrument. Scattering experiments can be perfor…
By hydrolysis of an ethanolic gallium nitrate solution, gamma-Ga2O3 was prepared as a single-phase polymorph having a specific surface area of 160 m2 g(-1). Surface acidity and basicity of this material was studied by IR spectroscopy, using pyridine, 2,6-dimethylpyridine, acetonitrile, and carbon dioxide as spectrosco…
Thin films obtained from a layer-by-layer deposition of a weak polycarboxylic acid and a positively charged globular protein were studied by in situ ATR-FTIR. The system was chicken egg lysozyme (Lys), bovine pancrease ribonuclease A (RNase), or bovine gamma-globulin (IgG) self-assembled with polycarboxylic acids. Whe…
The distortions in the square tellurium nets long known to exist in the structures of the charge-density wave materials, RETe3, have been elucidated. The (Te2)1- nets contain polytelluride oligomers which propagate in a fashion incommensurate from the adjacent (RETe)+ sublattice. The new information sets the stage for…
The excitation spectrum of a model magnetic system, LiHoF4, was studied with the use of neutron spectroscopy as the system was tuned to its quantum critical point by an applied magnetic field. The electronic mode softening expected for a quantum phase transition was forestalled by hyperfine coupling to the nuclear spi…
A series of copper catalysts supported on TiO2-ZrO2 with copper loading varying from 1.0 to 21.6 wt % were prepared by a wet impregnation method. The catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy, electron spin resonance (ESR),…
A novel laser molecular beam epitaxy (LMBE) system for the fabrication of atomically controlled oxides superlattices and an x-ray diffractometer that measures spatially-resolved x-ray diffraction spectra have been developed based on the concept of combinatorial methodology. The LMBE chamber has two moving masks, an au…
Electronic structures, exchange interaction mechanism between magnetic ions and Curie temperature of Vanadium - doped Nitrides (AlN, GaN, and InN) are studied within KKR-LSDA-CPA. It is found that the ferromagnetic super-exchange interaction mechanism is dominant at low concentrations of Vanadium, but the anti-ferroma…
Substances such as the ``telephone number compound'' Sr14Cu24O41 are intrinsically hole-doped. The involved interplay of spin and charge dynamics is a challenge for theory. In this article we propose to describe hole-doped Heisenberg spin rings by means of complete numerical diagonalization of a Heisenberg Hamiltonian…
The strip projection method is the most important way to generate quasiperiodic patterns with predefined local structure. We have obtained a very efficient algorithm for this method which allows one to use it in superspaces of very high dimension. A version of this algorithm for two-dimensional clusters and an applica…
We develop a theory of the linear optical spectrum of excitons in quantum dot molecules, including the effect of exciton-phonon coupling beyond the Markov limit. The model reproduces the general trend of the zero-phonon line broadening as a function of interdot distance, that were recently measured. The unexpectedly b…
Electron spin resonance spectra of copper phthalocyanine doped with alkaline metals (AxCuPc) have been investigated. The temperature dependence of ESR spectra indicates the ferromagnetic behavior. The Curie-Weiss temperature varies from 30K to 115K depending on the stoichiometry x of samples. Some particles of polycry…