羟氨苄青霉素引起大疱性类天疱疮样疹

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.

Advanced Thermoelectric Design: From Materials and Structures to Devices

https://hal.archives-ouvertes.fr/hal-00120432/document

Raman Spectroscopy of Nanomaterials: How Spectra Relate to Disorder, Particle Size and Mechanical Properties

We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

Theory of the linear and nonlinear optical properties of semiconductor microcrystallites

Optical phonon modes confined in nearly spherical InP quantum dots (QDs) prepared by colloidal synthesis were studied experimentally, by means of far-infrared (FIR) and Raman spectroscopy, and theoretically. Both FIR transmittance and Raman spectra contain some new features, compared to QDs of other polar semiconductor materials produced by the same technique. These peculiarities can be explained by the fact that there is a gap in the optical phonon band of bulk InP. Our calculations show that gap modes with angular momenta l>0 can appear in InP QDs when the high-frequency dielectric constant of the surrounding medium exceeds certain value. The gap modes are shown to determine the shape of the far-infrared and Raman spectra of the dots.

Raman and FIR studies of optical phonons confined in InP quantum dots

Thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different cobalt ferrite concentrations (x). The films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinnel structure. A slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation was observed. As the concentration of the cobalt ferrite increased, the grain size of the BaTiO3 phase decreased, from 91nm to 30nm, up to 50% CoFe2O4 concentration, beyond which the BaTiO3 grain size take values in the range 30-35nm. On the other hand the cobalt ferrite grain size did not show a clear trend with increasing cobalt ferrite concentration, fluctuating in the range 25nm to 30nm. The lattice parameter of the CoFe2O4 phase increased with increasingx. However, it was always smaller than the bulk value indicating that, in the films, the cobalt ferrite was under compressive stress that was progressively relaxed with increasing CoFe2O4 concentration. The magnetic measurements showed a decrease of coercive field with increasingx, which was attributed to the relaxation of the stress in the films and to the increase of particle agglomeration in bigger polycrystalline clusters with increasing cobalt ferrite concentration.

Structural and Magnetic Properties of Nanogranular BaTiO3-CoFe2O4 Thin Films Deposited by Laser Ablation on Si/Pt Substrates

/pdf/effect-of-self-defocusing-in-thin-films-of-close-packed-cds-2h44l7oxcq.pdf

EFFECT OF SELF-DEFOCUSING IN THIN FILMS OF CLOSE-PACKED CdS NANOCRYSTALS

Phonon modes in MOVPE grown In/sub 0.5/Ga/sub 0.5/P containing domains with CuPt-type ordering in the cationic sublattice along the [-111] and [1-11] directions were studied by means of FIR and Raman spectroscopy. The observed polarization dependence of the transmittance of the FIR radiation near 370 cm/sup -1/ suggests that this TO-type mode is characteristic not only of the disordered alloy, but also of the ordered InGaP/sub 2/. Ordering-related features observed by Raman spectroscopy include the extra (354 cm/sup -1/) phonon mode appearing (although not clearly resolved) in the allowed z(xy)z [001] scattering, and a clear difference between the spectra taken in z(x'x')z and z(y'y')z configurations. All these effects are noticeably smaller for the InGaP films with lower degree of ordering due to doping with Bi during its growth.

Anabela G. Rolo

Papers

Raman and FIR studies of optical phonons confined in InP quantum dots

Structural and Magnetic Properties of Nanogranular BaTiO3-CoFe2O4 Thin Films Deposited by Laser Ablation on Si/Pt Substrates

EFFECT OF SELF-DEFOCUSING IN THIN FILMS OF CLOSE-PACKED CdS NANOCRYSTALS

Spontaneous ordering in In/sub x/Ga/sub 1-x/P (x/spl ap/0.5) alloys: FIR and Raman spectroscopy studies

Silicon Dioxide Thin Films Doped with CdS Microcrystals Grown by Magnetron RF-Sputtering