The magnetization process of FeSi has been measured with a high-quality single-crystalline sample using a SQUID magnetometer in the temperature range from 5 K to 600 K. From the Arrott plots of the magnetization data, the fourth-order coefficient of the free energy is found to have a large positive value at low temperature and significantly decreases by the order of 10(5) with increasing temperature. This result can be explained with a new spin fluctuation theory of FeSi proposed by Takahashi.

In order to simulate the thermal behavior of one of the most useful inorganic–organic hybrid materials, octa-functional polyhedral oligomeric silsesquioxane (POSS), molecular dynamics (MD) simulations of crystals of POSSs having methyl, i -butyl, and cyclopentyl substituents were performed using the universal force field. The crystal structures obtained by the MD calculations were in good agreement with those reported based on experimental results. On the basis of their molecular expansion behaviors, the lattice lengths were also evaluated, from which the expansion of each lattice length as a function of temperature was found to be dependent upon the substituents.

First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. The alkali atom adsorption takes place near the six tetragonal bridge sites available on the cage, thereby avoiding the notorious clustering problem. Adsorption of alkali atoms involves a charge transfer process, creating positively charged alkali atoms and this polarizes the H 2 molecules thereby, increasing their binding energy. Li atom has been found to adsorb up to three hydrogen molecules with an average binding energy of 0.189 eV. The fully doped Li 6 B 36 N 36 cluster has been found to hold up to 18 hydrogen molecules with the average binding energy of 0.146 eV. This corresponds to a gravimetric density of hydrogen storage of 3.7 wt.%. Chemisorption on the Li 6 B 36 N 36 has been found to be an exothermic reaction, in which 60 hydrogen atoms chemisorbed with an average chemisorption energy of −2.13 eV. Thus, the maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 hydrogen molecules were adsorbed in molecular form.

We conducted DFT studies on the YnAlm binary clusters of size n + m <= 6, to study electronic property variation, using the PBE1PBE method and Lanl2DZ as basis set. The ground-state geometries of yttrium (n >= 4) prefer 3D geometry and Al (m <= 5) desires planar geometry. Yttrium clusters were stabilized by the addition of one or two aluminum atoms. The shape and geometry of the clusters has a profound influence on their band gap and stability. With an increase in the Al composition, segregation was found to occur in the bimetallic systems with the geometry and shape depending on the aluminum composition. The bimetallic clusters have higher electron affinity and stability. (C) 2009 Elsevier B.V. All rights reserved.

We study the electronic and atomic structures of hydrogenated silicon nanowires (SiNWs) by changing the mean diameter, morphology, and orientation using state-of-the-art density functional calculations. Most of the SiNWs are found to have large and direct band gaps, which make them very interesting for silicon-based nano-optoelectronic devices and lasers. The band gap increases with decreasing diameter in all cases because of quantum confinement, but the scaling is dependent on the morphology of the SiNWs. For thin [112] SiNW, the calculated band gap agrees well with the recent experiments. Variation in hydrogen concentration is used to explore the sensing capabilities of different surface morphologies and the associated surface reconstructions. Further studies on p- or n-doping show bulklike modifications in the electronic structure with several advantages that can be used to design nanoscale devices of SiNWs.

First-principles calculations of single molecular vibrations and the crystalline phonons of an anhydrous beta-(D)-glucopyranose monosaccharide crystal in the terahertz region were performed using periodic density functional theory (DFT) calculations. The calculated frequencies and eigenvectors of the phonon modes, which agreed with experimental results, did not correspond to those of the modes of a single molecule, mainly due to intermolecular hydrogen bonds and molecular deformation in the crystal. In addition, the phonon modes derived from molecular translations or rotations were estimated for a wide range of 46.2-312.4 cm(-1) by sampling the eigenvectors of the vibrational modes. (c) 2006 Elsevier B.V. All rights reserved.

First-principles calculations of the phonon modes of 4'-dimethylamino-N-methyl-4-stilbazolium tosylate in the terahertz region were performed using periodic density functional calculations. The calculated far-infrared (FIR) spectrum estimated from the phonon modes of the crystal did not correspond to the sum of the calculated spectra of the constituent cation and anion. The intramolecular modes of the methyl and sulfone group torsions and of pi-bridge bends were confirmed, including in-plane and out-of-plane intramolecular bending, with the intermolecular modes contributing to the FIR absorption of the collective peaks. The assignment of FIR-active modes provides fruitful ideas for the design and synthesis of promising derivatives. (c) 2006 Elsevier B.V. All rights reserved.

First-principles calculations of the crystalline vibrations of a lactose monohydrate crystal in the terahertz (THz) region were performed using periodic density functional theory calculations. The calculated vibrational modes in the THz region were derived from group motions with different sizes: molecules of lactose and crystal water, pyranose rings, and intramolecular frames. The intermolecular modes with large vibrational amplitude of lactose of 17.5-100.6 cm(-1) and of crystal-water of 136.1-237.7 cm(-1) were clearly separated. This article especially refers to the intermolecular vibrational modes of crystal water with the THz absorption, which provide detectable spectral features of hydrated crystals.

The surface and bulklike phonon modes of Si(100)c(4 X 2) nanometer-thin film were investigated using density functional calculations with a 4 x 4 supercell consisting of 10 layers. The surface phonon modes were dispersed over a wide range with two collective peaks around 120 and 190 cm(-1), including interference from both surface phonons. The distribution of the bulklike phonon modes revealed similar peaks to the bulk phonons, and the two collective peaks were newly confirmed on the lower frequency side. These characteristic peaks provide large spectral variation in the phonons of nano-thin films. (c) 2006 Elsevier B.V. All rights reserved.