Materials Literature
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Cristallisation dans le systeme orthohombique, groupe Pbca et affinement jusqu'a R=0,042. La structure est constituee de 3 tetraedres H 2 PO 3 non equivalents cristallographiquement, de molecules d'eau et d'atomes Mn et Na hexacoodines
From structural results previously reported the equilibrium conditions for ion-ion correlations in \ensuremath{\beta}-alumina are obtained. This provides a theoretical confirmation of the Beevers-Ross--mid-oxygen (BR-mO) model stability which whatever is the composition (1(5/3)) reveals itself to correspond to a lower…
We consider a finite superlattice consisting of unit cells with quantum wells filled with different types of carriers. The density-density correlation function is calculated with use of the random-phase approximation. The theory of resonant Raman scattering and inelastic electron scattering is formulated. The general…
The absorptances of 633-nm photons by silver island films formed on room temperature substrates were measured in an attenuated-total-reflection geometry by the photoacoustic method as a function of the angle of photon incidence. From the data obtained for s-polarized light ∊″, the effective dielectric function for the…
Long-range and local orders for ion-rich \ensuremath{\beta}- and \ensuremath{\beta}''-alumina are determined from conventional crystal-structure determinations and x-ray diffuse scattering. Both materials exhibit composition close to 1.66 ${\mathrm{Na}}^{+}$ per unit plane cell with a compensation mechanism exclusivel…
We study and compare plasmon spectra in semiconductor superlattices with periodic, quasiperiodic (e.g., Fibonacci sequence), and random spacings. Novel mode structures are found in the quasiperiodic cases, particularly for low values of level broadening that arises from inherent disorder effects. We discuss critically…
In any fluid or solid condensed phase, instantaneous atomic positions can be resolved into a combination of inherent packing and of vibrational deformation components. In principle the latter can be removed by quenching the system by (mass-weighted) steepest descent on the potential-energy hypersurface. Inherent struc…
Experiments on the transport of thermal energy through aggregates of small particles at low temperature are discussed. A transition to a weakly-temperature-dependent thermal conductivity, or plateau, appears at the temperature at which the thermal phonon wavelength equals the particle size. This is interpreted as evid…
Evidence from a number of previous experiments is found for Ag-cluster vibrations in enhanced Raman scattering from a Ag surface. By the analysis of the conditions specific to such experiments, the most likely identity of these clusters has been revealed to be ${\mathrm{Ag}}_{4}$${\mathrm{}}^{+}$. To further confirm t…
The reflective and absorptive contributions to the optical modulation in sputter-deposited thin films of crystalline LixWO3 have been determined as a function of lithium concentration (0<x<0.5). The magnitude of the reflective response increases with increasing substrate temperature (Ts) during depositio…
The one-dimensional Schr\"odinger equation with multiple scattering potentials is transformed to a discrete (tight-binding) form exactly. For a random configuration of potentials in which all the states are localized, it is shown (not argued) that the resistance \ensuremath{\rho} behaves as \ensuremath{\rho}\ensuremat…
We propose a simple decoration of the Penrose tiling to produce a two-dimensional quasi-crystalline model. We have used molecular dynamics simulation to invesigate the stability and the phase transitions of this system. Stable with pair potentials, it undergoes a first-order transition to the liquid phase. Its enthalp…
55 Mn spin-echo NMR spectra of RMn 2 compounds (R=heavy rare-earth) and their external field dependence have been measured in their magnetically ordered states. From the analysis of the 55 Mn hyperfine field, the Mn magnetic moments have been estimated as 2.6 and 2.5 µ B for GdMn 2 and TbMn 2 , respectively, whereas a…
Theoretical predictions for various neutral and charged forms of polyaniline are presented and discussed. The MNDO semiempirical method is used to predict geometries which serve as input for valence effective Hamiltonian (VEH) calculations of the electronic band structure. The VEH calculations provide predictions for…
Electron energy loss spectroscopy (EELS) has been used to study the adsorption of nitric oxide on Rh(111). NO adsorbs in twofold bridge sites at all coverages. The dissociation rate of NO on this surface at low coverage has been measured directly using EELS. The first order dissociation rate parameters are Ea =19.2±0.…
Les deux composes cristallisent dans le systeme orthorhombique, groupe PcaB. Coordination bipyramidale rhomboedrique et pyramidale rhomboedrique autour de En et Cu respectivement
NdDyFe14B shows a spin reorientation around TS =92 K which is lower than that obtained for Nd2Fe14B (150 K). Neutron diffraction on powder specimen indicates a preferential occupation for Dy atoms of the 4 f sites, but does not reveal the spin reorientation.
Angle-resolved valence photoemission spectra have been obtained for W(011) and W(001) using Al K\ensuremath{\alpha} and Mg K\ensuremath{\alpha} excitation and with both normal and off-normal emission directions. The angular resolution was \ensuremath{\lesssim}\ifmmode\pm\else\textpm\fi{}1.0\ifmmode^\circ\else\textdegr…
Initial steps in the photodissociation of nitrosyl ferrous and ferric heme complexes have been investigated by calculation of the ground and excited states and electronic spectra as a function of iron-ligand bond lengthening. The method used is an all valence semi empirical INDO-SCF-CI procedure with transition metal…
A b initio self-consistent field and configuration interaction (SCF-CI) calculations with a minimal basis set are carried out on a few lower π→π* states of free base porphin and free base chlorin. Excitation energies and oscillator strength of these states are calculated and are compared with observed values. For the…