Evaluation of the Solution Stability When Reconstructing the Volume Particle Size Distribution from Small-Angle X-Ray Scattering Data for a Silicasol Solution

The results of studying the stability of the solution to the problem for determining the volume nanoparticle size distribution using experimental small-angle X-ray scattering (SAXS) data for a silicasol solution are presented. The possibility of reconstructing solutions using indirect Fourier transform and nonlinear minimization methods for a two-component model of spherical polydisperse particles has been investigated. The results obtained are compared with the simulation data obtained previously for theoretical data sets.     

Performance assessment of new perturbed hard-sphere equation of state for molten metals and ionic liquids: Application to pure and binary mixtures

This work addresses modeling the pressure–volume–temperature (PVT) properties of molten metals and ionic liquids (ILs) using a new perturbed hard-sphere equation of state (PHS EOS). Two temperature-dependent parameters appeared in the EOS, are correlated with two scaling constants σ and ε. Knowing these parameters, the proposed EOS is applied to these classes of liquids. The reliability of the proposed model is checked by comparing with 3177 experimental density data points. The average absolute deviations (AAD) of predicted densities of molten metals and ILs from literature data are found to be 1.35% and 0.56%, respectively. The extension of PHS EOS to binary metal alloys and IL + IL is also discussed. Generally, 609 data points for binary mixtures have been examined. The AAD of the predicted results are found to be 1.03%.     

La3Ga5SiO14晶体电子结构及光学性质的第一性原理研究

采用基于密度泛函的第一性原理平面波赝势法对La3Ga5SiO14晶体基态的几何参量、能带结构、态密度和光学性质进行了系统的研究.优化了La3Ga5SiO14晶体中原子的内部坐标,利用精确计算的能带结构、态密度和电荷密度等值线分析了晶体的吸收谱、介电函数、折射率,计算结果与实验符合较好,为La3Ga5SiO14晶体材料的分子设计与应用提供了理论依据.     

Lattice dynamics and related properties of AIBIII and AIIBIV compounds,I. Elastic constants

The present state of knowledge of the elastic properties of the ternary chalcopyrite compounds and some related materials is reviewed. Results of experimental elastic constant determinations are critically evaluated by comparing with other experimentally available material parameters that directly depend on the elastic constants. Possible reasons for existing discrepancies and obvious inconsistencies in the experimental data are discussed. The results of theoretical calculations of the elastic constants of these compounds based on different theoretical models and approaches are compared with experimental data and are assessed concerning achievable accuracy and reliability. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Volume relaxation of a-Se studied by mercury dilatometry

Mercury dilatometry was used to study volume relaxation of amorphous selenium (a-Se). Influence of experimental setting and reactivity of a-Se with mercury was studied using two differently constructed dilatometers (dissimilar sensitivity of sample volume change and dissimilar values of characteristic time constants of the dilatometers). Three types of volume–time–temperature experiments were made. Temperature of glass transition and thermal expansion coefficients in glassy and liquid state were determined from non-isothermal experiments. Volume relaxation was studied mainly on the basis of isothermal experiments. It was found that classical isothermal relaxation experiments are strongly influenced by the loss of information at the experiment beginning due to the proceeding relaxation. On the other hand, more complex thermal history experiments seem to be less dependent on these procedural parameters and were considered as most suitable for studying structural relaxation. The reaction of a-Se and mercury was found not to be influencing the results of volume relaxation measurements.     

Atomistic study of elastic constants and thermodynamic properties of zinc – blende CuBr

Elastic constants and thermodynamic properties of zinc blende CuBr are calculated using a molecular dynamics simulation based on Tersoff empirical interatomic potential. We find that the elastic modulus C₁₁ is bigger than the other theoretical and experimental data, while C₁₂ is somewhat small. The elastic modulus C₄₄ is in good agreement with the theoretical calculations and experiment. Thermal expansion coefficient, specific heat capacity at constant volume and thermal conductivity are in very well agreement with experimental data. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A fluctuation theory of normal crystal growth for the very dilute binary metallic solid solution's crystallization in the case of macroscopic systems

A theory connected with spontaneous fluctuations of the limited spectrum solid state particle concentrations in the case of binary metallic macrosystems crystallizing from the binary melts is developed. Normal kinetics was found to be realized in the case of very dilute binary metallic solid solutions within the small ‘supercoolings’ region. A comparison between the theoretical and experimental data on the crystallization kinetics of very dilute binary metallic solid state solutions within the small ‘supercoolings’ region has been made. For some types of binary metallic macrosystems the quantitative restrictions of the supercooling regions within which a fluctuation mechanism and normal kinetics are assumed to act have been established. The restrictions are conditioned by some parameters of the binary macroscopic melt and two-phase transitional zone considered.     

The microstructural evolution of Al12Mg17 alloy during the quenching processes

The processes of rapid solidification for three cooling rates of Al₁₂Mg₁₇ alloy from liquid to solid are simulated using molecular dynamics based on embedded-atom method potentials derived by the force-matching approach. The liquid structures are calculated and the structural factors are in good agreement with experimental data. During each rapid quenching, an amorphous state is obtained, and the microstructures of the liquid, supercooled liquid, and the amorphous states of Al₁₂Mg₁₇ alloy are analyzed using the pair analysis technique.     

Transient and quasi‐stationary simulation of heat and mass transfer in Czochralski silicon crystal growth

The formation of grown‐in defects in silicon crystals is controlled by the concentration of intrinsic point defects. Under steady state conditions the type of the prevailing point defect species is linked to the ratio of pull rate and temperature gradient in the crystal at the solidification front. It has been shown that this ratio as well as computed point defect distributions are in good agreement with experimental data. In this paper we compare a coupled transient heat transfer and transient point defect transport model with quasi steady state simulations at various time steps. Both simulations show the same qualitative results, quantitative differences in temperature are less than 1 %. But already for constant pull rates the defect distributions show qualitative differences between transient and quasi steady state simulations. Therefore, for a detailed understanding how defects are related to growth conditions, the thermal history should not be neglected.     

Relation of the Hydrostatic Electrostrictive Coefficient of Cubic Dielectrics with other Material Constants

A simple relation is derived that links the hydrostatic coefficient of quadratic electrostriction with the volume compressibility and an expression involving the dielectric constant. The first part of the derivation is mainly macroscopic and applicable to dielectrics with cubic symmetry. Making use of the Born-Mayer potential, an expression of the derivative of the ionic polarizability with respect to volume is given in the second part. A negative sign of the hydrostatic coefficient is predicted for typical alkali halides. This result is in agreement with recent experimental findings reported in the literature, if the observed values are corrected for the influence of electrostatic stresses in an alternative way.     

Calculation of threshold voltage for phase-change memory device

Calculations of threshold voltage, which starts up transformation of active region in memory device from amorphous to crystalline state in phase-change random access memory, are reported. The calculations are based on the assumption that the emission of holes from the traps stimulates switching by forming conductive channel between electrodes. The results obtained by calculation correlate with the experimental data and the data reported in literature.     

Isobaric heating of polystyrene and evaluation of the Narayanaswamy parameter x from volume recovery data

Structure parameter x, defining the relative contributions of temperature and structure to the relaxation times, which is applied in Tool-Narayanaswamy-Moynihan (TNM) equation, was evaluated from volume heating isobars for polystyrene (PS) applying the peak shift method. The peak shifted with changing structural state of PS prior heating, which was reached by different period of aging time at 89 °C < T_g up to 2544 h. In this novelized procedure for volume data, originally tested only for enthalpic measurements, high sensitivity of peak temperature (position of inflection point of the heating isobar) was shown, together with high linearity of data. This allows to directly and sensitively calculate the shift and consequently structure parameter x. The value found in the research, x = 0.40 ± 0.02, is in good agreement with published results obtained by the peak-shift method from enthalpy data of PS.     

Electrical properties of GaAs induced by the metastability of EL2 defect

Metastable properties of EL2 defect in undoped semiinsulating GaAs have been studied using photocurrent and thermally stimulated current techniques (TSC). The experimental data suggest that light induced defect reaction takes place when EL2 is transferred to its metastable state.     

Characterisation of structures grown by Movpe using x-ray diffraction

This paper describes the double and triple axis diffractometers available for characterising heteroepitaxial layer structures in the laboratory environment. The relative merits of the techniques are described.To demonstrate the materials information available from the diffractometer data (usually referred to as rocking curves) examples are given of the analysis of layer thickness and lattice parameter values for single heteroepitaxial layers, two layer structures and multiquantum well structures. For layers with a defect density of less than 10⁵ per cm² detailed analysis of rocking curve data is carried out by comparing experimental results with simulated data.X-ray diffraction also offers a non-destructive means of fully characterising the state of relaxation of strained layer systems.     

Possible Ultrasonic Evidence for the Existence of Vortex-Antivortex Pairs

The attenuation of surface acoustic waves in the 700 MHz frequency range passing through 1000 Å NbN films has been measured on several NbN films. The films have a columnar structure where the columns are about 200 Å in diameter separated by 20 Å voids. In the superconducting state the attenuation does not follow the usual BCS curve. It appears to be composed of the sum of a BCS curve plus another curve which has a maximum below the superconducting transition temperature. The attenuation data may also be analyzed to yield an effective energy gap which is quenched at about one fifth of the BCS zero temperature energy gap. Tentatively, the Kosterlitz-Thouless vortex-antivortex model is used to determine the temperature dependence of an effective order parameter that yields reduced attenuation data which agree qualitatively with the experimental results.     

A low-frequency Raman study of glassy,supercooled and molten silica and the preservation of the Boson peak in the equilibrium liquid state

A temperature dependent Raman spectroscopic study of the Boson peak in silica is being presented. For the first time experimental data are obtained not only above the glass transition temperature but also above the melting point. The intriguing temperature dependencies exhibited by the Boson peak frequency and intensity are examined in detail. A comparison of the above features between the frequency-reduced and the true excess density of vibrational states revealed that the spectrum of the latter does not exhibit the anomalous trend of the Boson peak as regards the temperature dependence of its frequency, and further the number of the excess modes decreases with increasing temperature. The observability of the Boson peak in the normal liquid state as a well-resolved peak is also discussed in the context of recent theoretical and simulation works that relate the Boson peak with the details of the potential energy landscape of the supercooled liquid.     

Band intensities in the circular dichroism and absorption spectra and the states of <Emphasis Type="Italic">d</Emphasis> ions in absorbing media: I. Octahedrally coordinated positions of <Emphasis Type="Italic">d</Emphasis> ions

The factors affecting the band intensity in circular dichroism (CD) and absorption spectra (selection rules, point group of structural position, and the electron density of the ground state of octahedrally coordinated d ion in absorbing medium) are considered. The intensities of CD and absorption bands are calculated and compared with the experimental data. It is shown that the differences in the spatial inversion of the electric- and magnetic-dipole moment transformations lead to a more rigorous validity of the symmetry selection rules and increase the resolution of peaks and transparency window of medium absorption in CD spectra (in contrast to absorption ones). Some criteria for estimating the valence and structural states of d ions are formulated.     

Formation of an internal bias field in chromium-and L, α-alanine-doped triglycine sulfate crystals

The unipolar state of a chromium-and L, α-alanine-doped ferroelectric triglycine sulfate (TGS) crystal has been studied. The experimental data on the distribution of internal bias fields with respect to a seed are considered. The possible mechanisms of the formation of an internal bias field during the growth of TGS crystals with a low impurity concentration are considered.     

An interface clusters mixture model for the structure of amorphous silicon monoxide (SiO)

The present state of research on the structure of amorphous silicon monoxide (SiO) is reviewed. The black, coal-like modification of bulk SiO is studied by a combination of diffraction, microscopy, spectroscopy, and magnetometry methods. Partial radial distribution functions of SiO are obtained by X-ray, neutron and electron diffraction. Disproportionation of SiO into Si and SiO₂ is verified. High resolution TEM gives an upper limit of less than 2 nm for the typical Si cluster size. The Si K-edge electron energy-loss near-edge structure (ELNES) data of SiO are interpreted in terms of the oxidation states Si⁴⁺ and Si⁰. X-ray photoelectron spectroscopy gives first details about possible stoichiometric inhomogeneities related to internal interfaces. The wipe-out effect in the ²⁹Si MAS NMR signal of SiO is confirmed experimentally. The new estimation of the wipe-out radius is about 1.1 nm. First-time W-band, Q-band, and X-band ESR and SQUID measurements indicate an interfacial defect structure. Frequency distributions of atomic nearest-neighbours are derived. The interface clusters mixture model (ICM model) suggested here describes the SiO structure as a disproportionation in the initial state. The model implies clusters of silicon dioxide and clusters of silicon surrounded by a sub-oxide matrix that is comparable to the well-known thin Si/SiO₂ interface and significant in the volume because of small cluster sizes.