1998 국민건강·영양조사 - 계절별 영양조사

This Minireview aims to give an introduction to beryllium chemistry for all less-experienced scientists in this field of research. Up to date information on the toxicity of beryllium and its compounds are reviewed and several basic and necessary guidelines for a safe and proper handling in modern chemical research laboratories are presented. Interesting phenomenological observations are described that are related directly to the uniqueness of this element, which are also put into historical context. Herein we combine the contributions and experiences of many scientist that work passionately in this field. We want to encourage fellow scientists to reconcile the long-standing reservations about beryllium and its compounds and motivate intense research on this spurned element. Who on earth should be able to deal with beryllium and its compounds if not chemists?

Off the Beaten Track—A Hitchhiker's Guide to Beryllium Chemistry

Boron nitride (BN) nanostructures with complementary functions to their carbon counterparts are one of the most intriguing nanomaterials. Here we devote a compact review on the syntheses of BN nanomaterials: typical zero-dimensional (0D) fullerenes and nanoparticles, one-dimensional (1D) nanotubes and nanoribbons, two-dimensional (2D) nanosheets as well as three-dimensional (3D) nanoporous BN. Combining low-dimensional quantum confinement and surface effects with unique physical and chemical properties of BN, e.g. excellent electric insulation, wide band gap, and high chemical and thermal stability, BN nanomaterials have drawn particular attention in a variety of potential applications, e.g. luminescence, functional composites, hydrogen accumulators, and advanced insulators, which are also reviewed.

Recent Progress on Fabrications and Applications of Boron Nitride Nanomaterials: A Review

Small carbon clusters (Cn, n = 2-15) are produced in a molecular beam by pulsed laser vaporization and studied with vacuum ultraviolet (VUV) photoionization mass spectrometry. The required VUV radiation in the 8-12 eV range is provided by the Advanced Light Source (ALS) at the Lawrence Berkeley National Laboratory. Mass spectra at various ionization energies reveal the qualitative relative abundances of the neutral carbon clusters produced. By far the most abundant species is C3. Using the tunability of the ALS, ionization threshold spectra are recorded for the clusters up to 15 atoms in size. The ionization thresholds are compared to those measured previously with charge-transfer bracketing methods. To interpret the ionization thresholds for different cluster sizes, new ab initio calculations are carried out on the clusters for n = 4-10. Geometric structures are optimized at the CCSD(T) level with cc-pVTZ (or cc-pVDZ) basis sets, and focal point extrapolations are applied to both neutral and cation species to determine adiabatic and vertical ionization potentials. The comparison of computed and measured ionization potentials makes it possible to investigate the isomeric structures of the neutral clusters produced in this experiment. The measurements are inconclusive for the n = 4-6 species because of unquenched excited electronic states. However, the data provide evidence for the prominence of linear structures for the n = 7, 9, 11, 13 species and the presence of cyclic C10.

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Ionization Thresholds of Small Carbon Clusters: Tunable VUV Experiments and Theory - eScholarship

This volume contains a valuable database of updated results in the field of hydrogen storage materials, based on an extended and selected reference list. Possible directions of research for further developments are also included. It is part of the online platform SpringerMaterials which is the world's largest resource for physical and chemical data in the material science. Storing hydrogen in solids is widely thought to be one of the most promising solutions to the issue of safe, compact and affordable hydrogen storage for its use as energy carrier. As a result, the search of efficient hydrogen storage materials with adapted properties for the applications, such as high gravimetric and volumetric capacities, reversibility near room temperature and atmospheric pressure, fast kinetics etc., has attracted a vast amount of attention. In the first part of the book, the state of the art of materials that can be used for hydrogen storage is presented. The second part of the volume is devoted to the hydrogen technology, such as fuel cells, batteries, microsensors and detectors, energy conversion and chemical agents, extending the range of hydride materials applications to different fields. All the authors of the volume contributed significantly to the development of hydrogen storage materials as well as their technical applications. Representative results are included in the volume and comprehensively and critically analysed. The volume is recommended for all those involved in the field of hydrogen storage materials and their technical applications.

Hydrogen Storage Materials

Binding energies of small lithium clusters: A comparison of different theoretical calculations

In order to study quantum effects in a two-dimensional crystal lattice of a free-standing monolayer graphene, we have performed both path-integral Monte Carlo (PIMC) and classical Monte Carlo (MC) simulations for temperatures up to 2000 K. The REBO potential is used for the interatomic interaction. The total energy, interatomic distance, root-mean-square displacement of the atom vibrations, and the free energy of the graphene layer are calculated. The obtained lattice vibrational energy per atom from the classical MC simulation is very close to the energy of a three-dimensional harmonic oscillator $3{k}_{B}T$. The PIMC simulation shows that quantum effects due to zero-point vibrations are significant for temperatures $Tl1000$ K. The quantum contribution to the lattice vibrational energy becomes larger than that of the classical lattice for $Tl400$ K. The lattice expansion due to the zero-point motion causes an increase of 0.53% in the lattice parameter. A minimum in the lattice parameter appears at $T\ensuremath{\simeq}500$ K. Quantum effects on the atomic vibration amplitude of the graphene lattice and its free energy are investigated.

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Quantum effects in a free-standing graphene lattice: Path-integral against classical Monte Carlo simulations

Using the fixed-node diffusion quantum Monte Carlo method, we calculate the total energy of small cationic and neutral lithium clusters. We estimate the ionization potential, atomic binding energy, dissociation energy, and the second difference in energy. We present a critical analysis of the structural and electronic properties of the clusters. The bond lengths and binding and dissociation energies obtained from the calculations are in excellent agreement with the available experimental results. A comparative analysis of the dissociation energy and the second difference in energy indicates that the cationic clusters Li3+, Li5+, and Li7+ are the most stable ones. We have also studied the electron correlation effects in the lithium clusters. The cationic clusters of odd-number size are relatively more favored in terms of correlation energy than their neighbors of even-number size. In the range of cluster sizes under investigation, we find that the contribution of electron correlation to ionization potential is not larger than 28% of its total values, whereas it enhances significantly the dissociation energy of the clusters reaching up to 70% of its total values for the most stable ones.

A quantum Monte Carlo study of the structural and electronic properties of small cationic and neutral lithium clusters

Correlation effects on aromaticity of Be32- cluster: A quantum Monte Carlo study

Using fixed-node diffusion quantum Monte Carlo (DMC) simulation we investigate the structural properties and energetics of the linear and cyclic carbon clusters ${\mathrm{C}}_{n}$ for $n\ensuremath{\le}10$. We calculate the binding energy, the electron correlation energy, the dissociation energy, and the second difference in energy. We also present an analysis of the structural properties of the clusters. It is found that the bond lengths, binding energies, and dissociation energies obtained from the DMC calculations are in excellent agreement with the available experimental results. The electron-correlation contribution to the binding energy indicates that in the case of the linear isomers, the clusters of odd-number size are relatively more favored than their neighbors of even-number size, whereas for the cyclic isomers, we do not observe the oscillation pattern. In the range of cluster size under investigation, we find that the electron-correlation impact in the binding energy of the cyclic clusters is larger than that of the corresponding linear ones, varying from $30%$ to $40%$ of the binding energy values. The electron correlation is also essential to the stability of the clusters enhancing by up to $52%$ their dissociation energy. A comparative analysis of the dissociation energy and second difference in energy indicates that the linear isomers ${\mathrm{C}}_{3}$ and ${\mathrm{C}}_{5}$ are the most stable ones.

B. G. A. Brito

Papers

Binding energies of small lithium clusters: A comparison of different theoretical calculations

Quantum effects in a free-standing graphene lattice: Path-integral against classical Monte Carlo simulations

A quantum Monte Carlo study of the structural and electronic properties of small cationic and neutral lithium clusters

Correlation effects on aromaticity of Be32- cluster: A quantum Monte Carlo study

Quantum Monte Carlo study on the structures and energetics of cyclic and linear carbon clusters C n ( n = 1,...,10)