We have performed an approximate ab initio calculation of vibrational properties of hydrogenated amorphous silicon (a-Si:H) using a molecular dynamics method. A 216-atom model for pure amorphous silicon (a-Si) has been employed as a starting point for our a-Si:H models with voids that were made by removing a cluster of silicon atoms out of the bulk and terminating the resulting dangling bonds w...

Enantiomeric amino acids have specific physiological functions in complex biological systems. Systematic studies focusing on the solid-state properties of d-amino acids are, however, still limited. To shed light on this field, structural and spectroscopic studies of d-alanine using neutron powder diffraction, polarized Raman scattering and ab initio calculations of harmonic vibrational frequenc...

A polarizable ionic interaction potential, constructed from first-principles calculations, is used to examine the structure, vibrational spectra, and transport properties of molten mixtures of LiF and BeF2 across a range of compositions. The simulations reproduce the experimentally measured vibrational frequencies of the fluoroberyllate (BeF4(2-)) ions, which form in the melt, as well as conduc...

The structures of free-standing gold nanowires are studied by using molecular-dynamics-based genetic algorithm simulations. Helical and multiwalled cylindrical structures are found for the thinner nanowires, while bulk-like fcc structures eventually form in the thicker nanowires up to 3 nm in diameter. This noncrystalline-crystalline transition starts from the core region of nanowires. The vibr...

The fundamental relations governing the geometry of carbon nanotubes are reviewed, and explicit examples are presented. A framework is given for the symmetry properties of carbon nanotubes for both symmorphic and non-symmorphic tubules which have screw-axis symmetry. The implications of symmetry on the vibrational and electronic structure of ID carbon nanotube systems are considered. The corres...

In this work, we explore the use of the semiclassical initial value representation (SC-IVR) method with first-principles electronic structure approaches to carry out classical molecular dynamics. The proposed approach can extract the vibrational power spectrum of carbon dioxide from a single trajectory providing numerical results that agree with experiment and quantum calculations. The computat...

Interstitial oxygen in silicon (Si:O) is a model system for the study of vibrational modes in semiconductors. Hydrostatic pressure has been used to probe the vibrational properties of this defect. In this paper, the results of infrared (IR) spectroscopy experiments on Si : O and Si : O are reviewed. As pressure is applied, the oxygen atom buckles outward. This structural change results in a qua...

OBJECTIVE This study aimed to investigate the effects of low-magnitude, high-frequency vibration with rest days on bone quality at multiple levels. METHODS Forty-nine three-month-old male Wistar rats were randomly divided into seven groups, namely, vibrational loading for X day followed by X day rest (VLXR, X = 1, 3, 5, 7), vibrational loading every day (VLNR), tail suspension (SPD), and base...

Anion clusters formed between a chloride or bromide anion and H2S molecules have been investigated using ab initio methods. Cluster structures, binding energies, and vibrational properties were predicted at the MP2 level with basis sets of aug-cc-pvtz and aug-cc-pvdz quality. Vibrational self consistent field (VSCF) calculations were employed to correct the predicted harmonic vibrational freque...

When a hydrogen molecule in a parahydrogen crystal is excited to a high vibrational overtone state, its electronic properties vary significantly since the energy of excitation is a sizable fraction of the energies of the excited electronic states. Thus the vibrational excitation leads to a significant variation of the intermolecular potential and resultant local distortion of the crystal lattic...