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Hydrogen storage in new nano-structured carbonic materials is a topic for lively discussion. The measured storage capacities of these materials, which have been announced in the literature during the last ten years are spread over an enormous range from about 0.1 wt% up to 67 wt%. This paper will give a report on the state of the art of hydrogen storage in carbon nano-structures. We shall critically review the recent ‘key publications’ on this topic, which claim storage capacities clearly above the technological bench mark set by the US Department of Energy, and we shall report new results which have been obtained in a joint project sponsored by the Federal Ministry for Education and Research in Germany (BMBF). To cite this article: M. Becher et al., C. R. Physique 4 (2003).

In this paper we review the existing theoretical literature on hydrogen storage in single-walled nanotubes and carbon nanofibers. The reported calculations indicate a hydrogen uptake smaller than some of the more optimistic experimental results. Furthermore the calculations suggest that a variety of complex chemical processes could accompany hydrogen storage and release.

The structural and optical properties of β-FeSi 2 precipitates produced by ion beam synthesis have been investigated by transmission electron microscopy, photoluminescence (PL) analysis and near infrared transmission measurements. The PL spectrum of β-FeSi 2 precipitates in a dislocation free sample has been observed to consist of a sharp line at 1.54 μm and a weak peak at 1.46 μm. Optical transmission measurements showed a direct band gap about 0.8 eV smaller than in continuous β-FeSi 2 film. Calculation of the electronic bands of β-FeSi 2 for different values of the lattice parameters indicates that this reduction can be ascribed to band distortion provided by the lattice strain.

We report density-functional calculations based on the local-density approximation (LDA) of the properties of doped barium bismuthates. Using the linear-response approach developed in the framework of the linear muffin-tin-orbital method the phonon spectrum of the ${\mathrm{Ba}}_{0.6}{\mathrm{K}}_{0.4}{\mathrm{BiO}}_{3}$ system is calculated and is compared with the results of the neutron-diffraction measurements. The effect of doping in the calculation is modeled by the virtual crystal and mass approximations. The electron-phonon coupling constant $\ensuremath{\lambda}$ is then evaluated for a grid of phonon wave vectors using the change in the potential due to phonon distortion found self-consistently. A large coupling of the electrons to the bond-stretching oxygen vibrations and especially to the breathinglike vibrations is established. Also, a strongly anharmonic potential well is found for the tiltinglike motions of the oxygen octahedra. This mode is not coupled to the electrons to linear order in the displacements; therefore an anharmonic contribution to $\ensuremath{\lambda}$ is estimated using the frozen-phonon method. Our total (harmonic plus anharmonic) $\ensuremath{\lambda}$ is found to be 0.34. This is too small to explain high-temperature superconductivity in ${\mathrm{Ba}}_{0.6}{\mathrm{K}}_{0.4}{\mathrm{BiO}}_{3}$ within the standard mechanism. Finally, based on standard LDA and LDA+$U$ like calculations, a number of properties of pure ${\mathrm{BaBiO}}_{3}$ such as tilting of the octahedra, breathing distortion, charge disproportionation, and semiconducting energy gap value is evaluated and discussed in connection with the negative-$U$ extended Hubbard model frequently applied to this compound.

In this paper we show that the orthorhombic phase of ${\mathrm{FeSi}}_{2}$ (stable at room temperature) displays a sizable anisotropy in the infrared spectra, with minor effects in the Raman data too. This fact is not trivial at all, since the crystal structure corresponds to a moderate distortion of the fluorite symmetry. Our analysis is carried out on small single crystals grown by flux transport, through polarization-resolved far-infrared reflectivity and Raman measurements. Their interpretation has been obtained by means of the simulated spectra with tight-binding molecular dynamics.

Density functional calculations based on local density approximation (LDA) of the properties of doped barium bismuthates are reported. Using a linear-response approach within the linear-muffin-tin-orbital method the phonon spectrum of Ba0.6K0.4BiO3 is calculated. The electron–phonon coupling constant λ is then evaluated for a grid of phonon wavevectors using the self-consistent change in the potential due to phonon distortion. Anharmonic contributions to λ from the tilting of oxygen octahedra are also evaluated on the basis of the frozen-phonon approach.

We study via density functional-based molecular dynamics the structural and dynamical properties of the rare earth silicon amorphous alloy Y_xSi_{1-x} for x=0.093 and x=0.156. The Si network forms cavities in which a Y^{3+} cation is entrapped. Its electrons are transferred to the Si network and are located in the dangling bonds of the Si atoms that line the Y cavities. This leads to the presence of low coordinated Si atoms that can be described as monovalent or divalent anions. For x=0.156, the cavities touch each other and share Si atoms that have two dangling bonds. The vibrational spectrum is similar to that of amorphous Si. However, doping induces a shoulder at 70 cm^{-1} and a pronounced peak at 180 cm^{-1} due to low coordinated Si., Comment: 4 pages, 4 figures

We show that tight-binding molecular dynamics provides a detailed description of the relations between structural deformations and changes in the electronic features during a Jahn-Teller process. In this case the metal-semiconductor displacitive phase transition occurring in epitaxial FeSi2 with film thickness can be correctly reproduced and interpreted by variable cell molecular dynamics for the bulk configuration. We show that it actually corresponds to a pattern of local Jahn-Teller distortions occurring at selected sites in different times, so that the configurational evolution cannot be described by a global coordinate.

The authors report the case, non forming part of any known syndrome, of a newborn with encephalocele, high cranial schisis, ocular anomalies, cleft palate and congenital clubfoot. The photographic documentation of the malformations is not possible due to a technical error in taking the photographs (lack of light in the room). Alterations to cerebral nervous tissue were histologically and cytologically characterised by immaturity and block of normal development during the early stages. For this reason the alteration of primary neuro-ectodermal tissue appears to be the initial factor with secondary involvement of anatomically and functionally contiguous fields and tissues, such as cranial bones and the eyes. The alteration of the nervous system resulted in the incapacity of the fetus to make fetal movements, making it vulnerable to extrinsic compression, above all uterine pressure. This led to the adoption of fixed postures with articular blockage most evident in the lower limbs (congenital clubfoot). The pathogenic noxa was not identified.

ive hundred and sixty-six women, consecutively admitted to nine different hospitals for elective abdominal hysterectomy, were randomized to receive a single 2 g i.v. dose of either cefotetan or piperacillin at induction of anesthesia. Five patients were excluded and 561 (287 given cefotetan and 274 given piperacillin) could be evaluated. In 10 patients (5 for each drug) the concentrations of either cefotetan or piperacillin in serum and subcutaneous tissue at the beginning and at the end of surgery andin uterus, salpinx and ovary samples, were microbiologically assessed. Adverse events to prophylactic drugs were never observed. No significant differences could be found between cefotetan and piperacilin groups for any of the considered infectious complications (bacteremia, wound or vaginal cuff infection, pelvic cellulitis and febrile morbidity) nor for the pooled data (cefotetan group: 4.9%, piperacillin group: 5.8%, p:NS). As for the concentrations of prophylactic drugs, serum levels throughout surgery were found to be adequate