Average Force Constant Research Articles

Concentration dependence of partial vibrational spectra in Ni–Nb and Cu–Zr metallic glasses

The neutron inelastic scattering of the Ni44Nb56 and Cu33Zr67 metallic glasses with isotope substitution for Cu and Ni were measured. The results are compared to earlier data for Ni62Nb38 and Cu64Zr36 (Ni and Cu isotopic substitution). Availability of two samples with different isotope content for each system has enabled partial vibrational densities of states to be obtained for both materials. The ratios of average force constants, BNi/BNb and BCu/BZr, and mean-square atomic displacements, 〈u2〉, for Ni, Nb, Cu and Zr atoms are estimated. The interatomic interaction of the Ni and Cu atoms with respect to all neighbours is less than that of the Nb and Zr atoms. With decrease of the content of Ni and Cu atoms the differences of the average force constants in each system decline.

Data analysis for inelastic nuclear resonant absorption experiments

Inelastic nuclear resonant absorption method has been applied to study lattice dynamics. The data evaluation procedure for such experiments using synchrotron radiation is presented. Various moments of the measured spectra provide model-independent information on vibrational excitations, such as the recoilless fraction, the average kinetic energy per nucleus, and the average force constant. In addition, the partial phonon density of states is extracted assuming a harmonic lattice model. A measurement performed on α -iron is shown as an example.

A neutron inelastic scattering study of Cu 64Zr 36 and Ni 64Zr 36 metallic glasses

A neutron inelastic scattering study is presented of Cu 64Zr 36 metallic glass, with isotope substitution for Cu, and the results are compared to earlier data for Ni 64Zr 36 (Ni isotopic substitution). The availability of two samples for each system, with different isotope content, has enabled partial vibrational densities of states to be obtained for both materials. The ratios of the average force constants, B Cu/ B Zr and B Ni/ B Zr, are estimated to be 0.68 ± 0.1 and 0.73 ± 0.1, respectively. The interatomic interaction of the Cu and Ni atoms with respect to all neighbors is weaker than that of the Zr atoms.

Instantaneous normal mode spectra of quantum clusters

The spectrum of instantaneous normal mode (INM) frequencies of finite Lennard-Jones clusters is studied as a function of the extent of quantum delocalization. Configurations are sampled from the equilibrium distribution by a Fourier path integral Monte Carlo procedure. The INM spectra, average force constants and Einstein frequencies are shown to be interesting dynamical markers for the quantum delocalization-induced cluster solid–liquid transition. Comparisons are made with INM spectra of quantum and classical Lennard-Jones liquids. The methodology used here suggests a general strategy to obtain quantal analogs of various classical dynamical quantities.

Bonding Properties of the 1,2-Semiquinone Radical-Anionic Ligand in the [M(CO)(4-n)(L)(n)(DBSQ)] Complexes (M = Re, Mn; DBSQ = 3,5-di-tert-butyl-1,2-benzosemiquinone; n = 0, 1, 2). A Comprehensive Spectroscopic (UV-Vis and IR Absorption, Resonance Raman, EPR) and Electrochemical Study.

Rhenium and manganese complexes of the 3,5-di-tert-butyl-1,2-benzosemiquinone (DBSQ) ligand, [M(CO)(4)(DBSQ)], fac-[M(CO)(3)(L)(DBSQ)], and cis,trans-[M(CO)(2)(L)(2)(DBSQ)], with a widely varied nature of co-ligand(s) (L = THF, Me(2)CO, MeC(O)Ph, py, NEt(3), Ph(3)PO, SbPh(3), AsPh(3), PCy(3), P(OPh)(3), PPh(3), dppe-p, PPh(2)Et, P(OEt)(3), PEt(3)) were generated in solution and characterized as valence-localized molecules containing the radical-anionic DBSQ ligand bound to Re(I) or Mn(I) metal atoms. This is evidenced by the following. (i) Carbonyl stretching frequencies nu(C&tbd1;O) and average force constants k(av) are typical for Mn(I) or Re(I) carbonyls. (ii) Frequencies of the intra-dioxolene C=O bond stretching vibration, nu(C=O), lie within the 1400-1450 cm(-1) range which is diagnostic for coordinated semiquinones. (iii) EPR spectra indicate a very small spin density on the metal atom (0.2% < a(M)/A(iso) > 2.6%). (iv) Absorption spectra show Re(I) --> DBSQ MLCT electronic transitions characterized by a resonant enhancement of the Raman peaks due to the nu(C&tbd1;O) and intra-DBSQ nu(C=O) vibrations. (iv) Finally, the electrochemical pattern consists of DBSQ/DBQ and DBSQ/DBCat ligand-localized redox couples. All these properties are, in a limited range, dependent on the nature and, especially, the number of co-ligands L, indicating a small delocalization of the singly occupied MO of the DBSQ ligand over the metal atom. The extent of this delocalization may be finely tuned by changing the co-ligands, although in absolute terms, it remains rather limited, and the DBSQ ligand behaves toward Re(I) and Mn(I) as a very weak pi-acceptor only. The changes of the electronic properties of the metal center induced by the co-ligands are mostly compensated by more flexible M --> CO pi back-bonding as is manifested by large variations of the average C&tbd1;O stretching force constant.

Force and diffusion measurements in sub-Doppler laser cooling.

We present the first direct measurements of the velocity dependence of the average force and diffusion constant for the metastable neon atoms in a one-dimensional ${\mathrm{\ensuremath{\sigma}}}^{+}$${\mathrm{\ensuremath{\sigma}}}^{\mathrm{\ensuremath{-}}}$ laser cooling configuration. Force and diffusion are determined, respectively, from the deflection and broadening of a highly collimated atomic beam by its interaction with a pair of counter-running laser beams. The interaction time is much shorter than the characteristic damping time of the cooling process. The resulted force and diffusion measurements are compared with the results of both semiclassical and quantum Monte Carlo calculations.

An Interaction Model for Solid-Matrix Phosphorescence with Filter Paper via the Modulus of Filter Paper

The experimental values of Young's modulus for filter paper samples were obtained as a function of temperature. These experimental modulus values for the filter paper samples, along with literature modulus values for regenerated cellulose and chromatography paper, were used to derive equations that relate Young's modulus values of filter paper to the phosphorescence lifetimes of adsorbed phosphors on filter paper as a function of temperature. In addition, an equation was derived for one of the phosphors that relates the changes in phosphorescence quantum yield with temperature to Young's modulus. The basis for the equations is a theory for hydrogen-bond-dominated solids that considers Young's modulus as related to the average force constant for the hydrogen bonds in paper and the effective number of hydrogen bonds in paper. For all the systems investigated, linear relationships were obtained between ln(phosphorescence lifetime) and ln(Young's modulus). Also, a linear equation was obtained between ln(phosphorescence quantum yield) and ln(Young's modulus) for one of the phosphors. In general, the results of this work form the basis of a fundamental theory for the phosphorescence of compounds adsorbed on filter paper.

Calculation of Bond Lengths in InGaAsP Quaternary Alloy Semiconductor

The bond lengths in an lnGaAsP quaternary alloy semiconductor were defermined using valence-force-field and continuum models. The bond lengths tend to preserve those in binary compounds. The length deviation from that of a binary compound is small if the bond-stretching force constant is large and/or the average bond-bending force constant is small. Theoretical results agree well with those obtained by experiments involving extended-X-ray-absorption fine-structure measurements. The validity of the Vegard law for a lattice constant is discussed and a slight discrepancy from the law is interpreted.

ChemInform Abstract: The Average Structure and Force Constants of Gaseous Trichlorofluoromethane Determined by Electron Diffraction and Spectroscopy

Abstract The molecular structure and mean amplitudes of CC1 3 F have been determined by gas electron diffraction. General quadratic force constants have been derived from vibrational frequencies, Coriolis coupling constents, a centrifugal distortion constant and mean amplitudes. The zero-point average structure obtained by a joint analysis of electron diffraction and microwave spectroscopic data has been compared with structures given by molecular mechanics and ab initio calculations.

The average structure and force constants of gaseous trichlorofluoromethane determined by electron diffraction and spectroscopy

The molecular structure and mean amplitudes of CC1 3F have been determined by gas electron diffraction. General quadratic force constants have been derived from vibrational frequencies, Coriolis coupling constents, a centrifugal distortion constant and mean amplitudes. The zero-point average structure obtained by a joint analysis of electron diffraction and microwave spectroscopic data has been compared with structures given by molecular mechanics and ab initio calculations.

純鉄の結晶粒界に偏析した&lt;SUP&gt;119m&lt;/SUP&gt;Snを利用したSnの結合状態のメスバウアー解析

Mössbauer nuclei 119mSn were doped into the grain boundary of ultra fine grained iron specimens. Various parameters such as internal magnetic field, Debye temperatures and thermal jump frequency were measured. The parameters showed that tin atoms segregated at the grain boundary are contributing a less amount of outer shell electrons to bonds with the neighboring atoms and the average force constant is reduced below that of tin in solid solution in the iron matrix. The differences, however, were small while a large difference was noticed in its internal magnetic field. The absence in the internal magnetic field suggests that iron atoms next to tin in the grain boundary are in a special state with respect to their d-level and may explain the embrittlement of steel. The oxygen-induced embrittlement which was suggested from experiments of pure iron may be a different mechanism peculiar to pure iron.

Heat capacity measurements of GcS, GcSc and GcTc

The heat capacities of GcS. GcSc and GcTc were measured in the temperature range 220–610 K, employing a computer interfaced differential scanning calorimeter. Using the measured heat capacity data. the Debye temperatures of GcS, GcSc and GcTc were estimated to be 360, 280 and 180 K, respectively. The IV-VI compounds with cubic structure have lower average force constants than the orthorhombic compounds. The absolute entropics at 298 K were calculated to be 59.4 ± 4.0, 71.6 ± 4.0 and 97.5 ± 4.0 J K −1 molc −1 for GcS and GcTc, respectively.

On the relationship between ionic displacement and the curie temperature and spontaneous polarization in displacive ferroelectrics

It is suggested that measurements of the pressure dependence of the Curie temperature (Tc) and of the spontaneous polarization (Ps) are very useful in examining the relationships suggested by Abrahams, et al., for displacive ferroelectrics. These are relationships between Tc or Ps and the relative displacement (Az) developed by the homopolar metal ion (e.g. Ti in BaTiO3) along the polar axis. The necessary experimental data are available on BaTiO3, PbTiO3 and SbSI. The results show that the coefficient x appearing in the Tc(Δz) expression is not a true constant but increases substantially with increasing pressure. This increase is to be expected if x is qualitatively interpreted as an average force constant between the homopolar ion and the surrounding ions. The lattice dynamical implications of the results are discussed briefly.

Vibrational Bending and Stretching Frequencies for C4, C5 and C6

A correlation of electronic structure, developed from molecular-orbital considerations, with bending force constants for 15 linear molecular species containing carbon, nitrogen, and oxygen has produced estimates for the average bending force constants of C4, C5 and C6. These force constants are used to estimate a set of vibrational energy levels for each species to be used in calculations of the thermodynamic functions.

Low-Temperature Specific Heats of Titanium, Zirconium, and Hafnium

The specific heats of titanium, zirconium, and hafnium were found to obey the relation $c=\ensuremath{\gamma}T+\ensuremath{\beta}{T}^{3}$ from 1.1 to 4.5\ifmmode^\circ\else\textdegree\fi{}K within the experimental error. As in other transition metals, the electronic term is large and for the Group IV-A metals decreases with increasing atomic number indicating a progressively larger degree of electronic interaction in the sequence titanium, zirconium, and hafnium. The Debye temperatures decrease with increasing atomic mass as would be expected from the central-force model; however, the ratio of the Debye temperatures indicate that the average atomic force constant for hafnium is some 50% larger than for titanium and zirconium in agreement with the unusually small atomic volume of hafnium.

Infrared spectrum and molecular constants of CT 4

The bands, ν 3, ν 4, and 2 ν 3 of CT 4 have been observed. The ν CH band of CHT 3 was observed also. An analysis of the band ν 3 of CT 4 yields ν 3 = 1937.0 cm −1 and ζ 3 = 0.252. The data on CT 4 was combined with data in the literature of CH 4 and CD 4 to calculate average valence force constants for the methanes.