Vibrational modes of the stibine molecule

In this paper, we use the algebraic approach to describe the vibrational modes of stibine molecule (of C_3v molecular symmetry group) up to 21 quanta. As the stibine molecule exhibits stretch-bend resonances, we build an algebraic pyramidal coupling operator between stretching modes and bending modes adapted to this molecule. The standard deviation associated to the fit of the vibrational levels is 1.75 cm⁻¹.     

Vibrational modes of rare‐earth formates

In this work we investigate the room‐temperature Raman spectra of several rare‐earth [RE(HCOO)₃; RE = La, Pr, Nd, Gd, Tb and Y] formates. Polarized measurements were carried out for La(HCOO)₃ yielding the observation of most of the Raman‐active phonons predicted by group theory analysis. The respective assignment is given based on the formate vibrations and correlations with previous results in other RE(HCOO)₃ systems. The wavenumber ‘softening’ observed when RE goes from Y to La is accounted for the lattice expansion. Copyright © 2009 John Wiley & Sons, Ltd.     

中国现代二-音钟的振动方式

用全息干涉法对苏州乐器厂制造的扁钟的振动方式进行了研究。发现钟的非圆形状产生了许多成对的方式,其中一对的一个方式的节线在钟的隆起上,另一个方式在那里则是腹线。两个最低方式的频率比值为1.188,接近于小三度(1.189),这部分是由于钟上铸有六条调音槽的结果。     

Quantitative analysis of electronic properties of carbon nanotubes by scanning probe microscopy: from atomic to mesoscopic length scales

A new multiscale approach to the quantitative interpretation of scanning probe microscopy data in terms of the local electronic properties of 1D systems such as carbon nanotubes is presented. The interactions between a probe and the system are treated using a combination of first-principles density functional calculations and continuum electrostatics modeling. Realistic tip size effects are included using an image charge model. It is shown that the local potential at a nanotube on a substrate due to a probe can be calculated quantitatively, allowing experimental data to be analyzed in terms of the electronic structure of defects.     

Vibrational modes induced by a pair of impurities

Presence of a polarizable impurity atom in an ionic crystal induces a localized vibrational mode of the lattice. The frequency of the mode is distinct from the propagating modes of the pure crystal. It is shown in this paper that the frequency of the mode depends on the polarizability of the impurity atom and on the distance of separation between two adjacent impurities.     

Infrared spectroscopy of superionic conductor LiNaSO4: Vibrational modes and thermodynamics

Infrared active phonon spectra of lithium sodium sulphate, LiNaSO₄, were studied at temperatures between 20 K and 780 K. Dielectric constant [ε = ε′ + iε″] and energy loss function [− Im(1/ε)] were obtained from Kramers–Kronig analysis. Our IR data show a more complete set of vibrational modes than previous investigations. The IR data of LiNaSO₄ at 20 K are consistent with the P31c symmetry, indicating that LiNaSO₄ shows no structural phase transitions between 20 K and 300 K, in contrast to LiKSO₄. On heating from 20 K, phonon modes related to Li and Na vibrations show a dramatic line broadening and decrease in intensity. An extra mode is recorded near 380 cm^− 1 at 500 K. The absorption shows a systematic increase in intensity on further heating. These changes are attributed to anharmonic effects and Li diffusion or hopping. Dramatic spectral changes in the internal modes occur near 620 K on heating, suggesting the onset of the rotational disorder of SO₄ tetrahedra, but the Li atom spectrum shows weak response to the rotational disorder.     

Vibrational modes and phase transition of Si-Ge solid solution

We present the simplified treatment where the lattice vibrations of Si or Ge atoms in the Si-Ge solid solution are replaced with that of pure Si or Ge crystal at lattice constants of the alloy. Considering the volume effect on the force constants of the pure constituent, we obtain the phonon dispersion curves of the local and band modes for Si_0.91Ge_0.09 and Si_0.11Ge_0.89 systems and the concentration x-dependence of the local and band modes frequencies in the Si_1?xGe_x solid solutions. Then, from the calculation of the effective mode Grüneisen parameter γ_i for the average phonon modes in the Si_1?xGe_x systems, we obtain the predominant correlation between TA mode Grüneisen parameter γ^X_TA at the point X and the phase transition pressure P_t, and the softening of TA modes is related to the pressure-induced phase transition of the Si-Ge solid solution.     

Vibrational modes of oxygen on W(110)

Electron energy loss measurements of the vibrational modes of oxygen on W(110) as a function of coverage up to 0.5 monolayer are presented and analyzed. A single loss at 67 meV is observed initially; with increasing exposure this loss shifts to 72 meV and another loss appears at 47 meV. These data indicate coexistence of two species on the surface with a coverage-dependent conversion. Angular profiles of the specular elastic beam show a dramatic increase in width with initial oxygen coverage; this is possibly due to an oxygen-induced static disordering of the W surface layer.     

Calculation method for the continuum states of atomic systems

In the present work, we develop a calculational method of solving the scattering equations for spherically symmetric potentials by expanding the solutions on Coulomb functions. We utilize a multistep integration scheme together with the standard partial wave analysis in a region where the potential term dominates. The method applies to any physical problem expressed as [? ² + V(r) + k ²]ψ(r) = 0, while the extension of the method to more general scattering problems is briefly discussed. At present, we demonstrate a two-step Coulomb-fitted integration scheme by calculating the short-range scattering phase shifts for various potentials V (r).     

Adhesive contact: from atomistic model to continuum model

Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a self-consistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve.     

Vibrational modes and infrared absorption of interstitial oxygen in silicon

A quasi-linear Si₂O molecule model (QLMM) is suggested from an analysis of the configuration and the interactions of an isolated oxygen atom with its neighbor silicon atoms. The vibrational modes are assigned and the infrared absorption spectra are calculated in detail with the model. The theoretical results are in reasonably good agreement with reported experimental values. This agreement shows that for the analysis of the vibrational modes of the interstitial oxygen atom in silicon crystals it is not necessary to consider the coupling of the molecule with the rest of the lattice. The interaction of the oxygen atom with its six second-nearest silicon atoms only causes the level separation of the ₂ mode and the formation of the fine structure.     

Vibrational modes of sodium–tellurite glasses: Local structure and Boson peak changes

Raman spectra of xNa₂O−(1−x)TeO₂ glasses were measured and analyzed over a broad composition range. The network structure of the glass consists of a mixture of TeO₄ trigonal bipyramids and TeO₃ trigonal pyramidal units. Increase of alkali content results in conversion of the TeO₄ units into TeO₃ units with a varying number of non-bridging oxygen atoms. This local structure transformation becomes more evident at x=0.2, where rigidity percolation theory predicts a threshold for the rigid-to-floppy transition. However, other spectral features such as the composition dependence of the energy of the Boson peak do not support the occurrence of the stiffness transition. The controversial dependence of dynamical parameters such as the fragility index as a function of Na₂O concentration is also discussed.     

Iron oxide nanoparticles modified with oleic acid: Vibrational and phase determination

A simple path methodology to detect the phase composition of iron oxide nanoparticles modified with oleic acid based on vibrational spectroscopy is present here and applied on three different nanoparticles prepared by co-precipitation method. Firstly, the phase composition, magnetite, maghemite, and hematite, is determined using a reference intensity ratio methodology on X-ray diffraction pattern. Also, the size of each sample was calculated by Scherrer equation. Scanning, transmission electron microscopy, microanalysis and electron diffraction show a core magnetite particles size of around 10 nm for all particles. Based on lattice vibrations, we find a concentration of around 80% of magnetite and a hematite phase lower than 5%. Whereas, the magnetite composition from X-ray diffraction shows 76%. We also investigate the metal-organic interaction and disorder degree of organic molecule conformation by infrared and Raman spectroscopy analysis. Hematite lattice vibrations show more alterations as it interacts with the organic acid. Finally, magnetic measurements at room temperature of the modified particles, suggest a superparamagnetic behavior and high saturation magnetization.