Laser-Induced Plasma Atomic and Ionic Emission During Target Ablation

This paper investigates the spectroscopy of plasma that resulted from the bombardment of ZnSe by using the optical emission spectroscopic (OES) technique. The plasma can be generated by the reaction between an Nd:YAG laser, with a wavelength of 1064[Formula: see text]nm with a repeat rate of 6[Formula: see text]Hz (as well as 9[Formula: see text]ns pulse duration), and a solid target, where the density of the electron (ne), the temperature of the electron ([Formula: see text]), the frequency of the plasma ([Formula: see text]) and the Debye length ([Formula: see text]) as plasma parameters, in addition to the particles’ number of Debye ([Formula: see text]) and plasma parameter ([Formula: see text]) have been calculated by picking up the spectrum of plasma at different energies (100, 200, 300, 400, 500) mj using Selenium (Se), Zinc (Zn) and the mixture (ZnSe) at ([Formula: see text]). It is found that the electron temperatures of Zn and Se ranged between (0.257–0.267)[Formula: see text]eV and (1.036–1.055) eV, respectively, while that of ZnSe ranged between (1.15–1.28)[Formula: see text]eV. This indicates that the electron temperature of ZnSe is higher than the temperatures of each Zn and Se.

Магнитная восприимчивость нанокомпозитных редкоземельных титанатов в переменных полях

Experimental investigation of magnetic susceptibility of nanocomposite rare earth titanates at low temperatures is carried out in frequency range from 1 Hz to 10 kHz. Nanocomposites based on opal matrices are the objects under study which inter-spherical voids are filled with Gd2Ti2O7, Yb2Ti2O7, Dy2Ti2O7 и Dy2Si2O7 particles sized up to 60 nm. The frequency dependences of AC susceptibility are measured at temperatures from 2 to 20K. At frequencies above 1 kHz the frequency dependence fairly good corresponds to a relaxing oscillator model and can be approximated by Debye formula for all nanocomposites. For frequencies from 1 Hz to 10 kHz, however, it is necessary to apply a model with two relaxation times.

Modelling of high-symmetry nanoscale particles by small-angle scattering

A versatile procedure to build high-symmetry objects and to calculate their corresponding small-angle scattering intensity is presented. Starting from a set of vertex positions, available from a large and extensible database, it is possible to build several types of bodies using spherical subunits. A fast implementation, based on the Debye formula using a histogram of distance, is then used to compute the theoretical scattering intensity. Since the model is built from the definition of a small set of parameters, it is possible to perform an optimization of structural parameters against experimental data. Finally, affine size polydispersities can be easily included by the rescaling of the histogram of the positions used in the calculations. Several examples of the calculations are presented, demonstrating the method and its applicability.

DEBUSSY: a Debye user system for nanocrystalline materials

DEBUSSYis a new free open-source package, written in Fortran95 and devoted to the application of the Debye function analysis (DFA) of powder diffraction data from nanocrystalline, defective and/or non-periodic materials through the use of sampled interatomic distance databases. The suite includes a main program, taking the name of the package,DEBUSSY, and dealing with the DFA of X-ray, neutron and electron experimental data, and a suite of 11 programs, namedCLAUDE, enabling users to create their own databases for nanosized crystalline materials, starting from the list of space-group generators and the asymmetric unit content. A new implementation of the Debye formula is adopted inDEBUSSY, which makes the approach fast enough to deal with the pattern calculation of hundreds of nanocrystals, to sum up their contributions to the total pattern and to perform iterative algorithms for optimizing the parameters of the pattern model. The package strategy uses the sampled-distance database(s) created previously byCLAUDEand combines, for any phase, a log-normal or a bivariate log-normal function to deal with the sample-size distribution; four different functions are implemented to manage possible lattice expansions/contractions as a function of crystal size. A number of output ASCII files are produced to supply some statistics and data suitable for graphical use. The databases of sampled interatomic non-dimensional distances for cuboctahedral, decahedral and icosahedral structure types, suitable for dealing with noble metal nanoparticles, are also available.

Modelling the X-ray powder diffraction of nitrogen-expanded austenite using the Debye formula

Stress-free and homogeneous samples of nitrogen-expanded austenite, a defect-rich f.c.c. structure with a high interstitial nitrogen occupancy (between 0.36 and 0.61), have been studied using X-ray powder diffraction and Debye simulations. The simulations confirm the presence of deformation stacking faults in the structure, while twin or growth faulting can be ruled out. Screw dislocations are abundant and the dislocation density increases with the interstitial nitrogen occupancy. Whether the N atoms are clustered or distributed randomly among the octahedral interstices was found to be indistinguishable to X-ray powder diffraction.

Description of X-ray powder pattern of turbostratically disordered layer structures with a Rietveld compatible approach

We address the problem of the quantitative description of X-ray powder pattern of turbostratically disordered layer compounds. The Debye formula is used, which allows the aperiodic description of any arrangement of atoms. With the extension of Yang and Frindt (1996) for the ideal turbostratic case, these calculations are used to generate reference data that are subsequently treated by the Rietveld method. We are able to show that the case of uncorrelated turbostratic disorder can be modelled equally well in a periodic supercell approach with a single layer in the supercell that is suitable for the Rietveld technique. A brief introduction of this new model was given as an oral contribution at EUROCLAY 2003 (Ufer et al., 2003). The fundamental principles are described in this article because of its complexity. The applicability of this approach to real systems is demonstrated for smectite and corundum mixtures.