Papers by Keyword: Pair Correlation Function

Abstract: The heterogeneity of recrystallized subgrains is a substantial parameter which ought to be consider when controlling recrystallization fraction within a microstructure is needed. The statistical descriptor pair-correlation function is employed as stereological reference for reconstructing the nucleation sites spatial distribution within given volumes based on 2D data. The aim of the current study is to implement the 3D reconstructed particles distribution into a Monte Carlo approach to explore the evolution of microstructure in 7xxx Al alloy during homogenization process. Once the stored energy around the coarse particles is consumed recrystallizing grains the recrystallization is fulfilled. The simulated grain structures are qualitatively evolved in manner of the recrystallization of experimental data, and this verify that recrystallization process is mainly controlled by PSN mechanism.

Abstract: To investigate the interaction mechanism of PVA on the surface of HA, the molecular dynamics simulation was applied to simulate and calculate the binding energy between PVA of different monomers and HA crystallographic planes (001), (100) and (110), and then the mechanical properties and radial distribution function of the PVA/HA(110) system were calculated and analyzed. The results show that HA (110) has the higher binding energy with PVA than that of HA (001) and (100). The binding energy and the Young’s modulus of HA(110)/PVA system increase with the rising of PVA monomer number at the same crystallographic plane in a certain range, however, the descending trend takes place while monomers number reaching a certain value. This change trend is relating to the effective contact between two single components. By calculating the pair correlation function of HA(110)/PVA, there is a strong interaction between HA crystallographic plane (110) and PVA, it is mainly derived from the hydrogen bonds between O atoms of PVA and H atoms in HA crystal, besides, the ionic bonds interactions existing between O_a and Ca.

Abstract: The partial structure factors for liquid alloy In_1-xSn_x have been computed at varying concentration and temperatures using pseudopotential theory. The structure factor S(q) and pair correlation function g (r) have been determined using the hard-sphere approximation. The temperature dependent hard-sphere diameter σ (T) is estimated using Vσ=Vminr+12kBT criterion from the computed pair potential. The modified empty-core local pseudopotential, which represents the orthogonalisation effect due to s-core states, is used for electron–ion interaction with proper screening function. The only potential parameter, the core radius, is determined at different temperatures from the knowledge of structure factor. Intrinsic temperature effects have been studied through dimensionless damping term (see formula in paper) in the pair potential. The effect of temperature and concentration on structure factors is discussed to shed light on bonding in technologically important alloy. This used pseudopotential proved successful in explaining the structural properties of non-crystalline alloys at higher temperatures.

Abstract: This paper addresses the potential of molecular dynamics simulation for structure–property correlations in rubber. This is an important topic within a multi-scale framework to rubber blends. For that purpose, the Mechanical Properties of NR(Natural rubber)/TPI(Gutta percha) are studied by Molecular dynamics simulation method. The result indicates that the NR/TPI’s properties have been improved significantly. Compared to the pure TPI, the rubber blends’ Modulus and rigidity decrease while flexibility and strength are enhanced. Based on these, the pair correlation functions are discussed, the best simulation technique identified in this study reveal the nature of interactions between the components of the blends.

Abstract: The structure properties of magnetic fluids are studied in the absence of an external magnetic field focusing the main attention on the influence of ferroparticle polydispersity. Magnetic fluid is modeled by a bidisperse system of uniformly magnetized hard spherical particles with permanent magnetic moments. The magnetic fluid microstructure is described with the help of the pair correlation function, and the ferroparticle polydispersity is taken into account within the bounds of bidisperse system. For the parameters, which are typical for real commercial magnetic fluids, we have obtained that the majority of ferroparticles (small is sizes) are less correlated. At the same time the large particles, which are small in number, are strongly correlated.

Abstract: Structural and dynamical properties of the rapid solidification process of liquid Ge have been investigated by molecular-dynamics calculations based on the Stillinger-Weber potential. The variations of microstructures during the solidification process are analyzed by the self-diffusion coefficient D(T), pair correlation function g(r) curves and the HA bond-type index method. The melting point implicated in D(T) is about 2100 K. The pair correlation function g(r) obtained by the simulated in liquid Ge is good agreement with experiment, the fist-peak of g(r) gradually becomes higher and sharper with the temperature decreasing, when temperature drops to 1400 K, the second-peak of g(r) begins to split. The change of HA bond-type indicated that the most important structural change occurs in the temperature range 1400 K-700 K.

Abstract: An evolution of the structure of three glasses of Na2O-Nb2O5-SiO2 system in the course of isothermal heat treatments at 660–700°C and the extinction coefficient of the material were studied. Spinodal phase separation was found to be a primary process followed by precipitation of nano-sized NaNbO3 crystalline phase. It was found that the spectral dependence of the extinction coefficient in the wavelength range λ= 400–800 nm corresponds to light scattering by spinodal structure at the phase separation stage and by independent Rayleigh scatterers (NaNbO3 nanocrystals) at the early stage of crystallization. The extinction coefficient increases at the first half of the crystallization stage and then decreases. At the late stage of crystallization and for the final glass-ceramics, the extinction coefficient α is 10–20 times smaller than that calculated for independently scattering nanocrystals and is characterized by anomalous wavelength dependence (α ∝ λ−6). The model for calculation of extinction coefficient is proposed, in which the interference effects in light scattering by nanocrystals are taken into account. On this basis, the variation of extinction coefficient in the course of crystallization and its wavelength dependence are explained.

Abstract: This paper describes some aspects of reconstruction of microstructures in three dimensions. A distinction is drawn between tomographic approaches that seek to characterize specific volumes of material, either with or without diffraction, and statistical approaches that focus on particular aspects of microstructure. A specific example of the application of the statistical approach is given for an aerospace aluminum alloy in which the distributions of coarse constituent particles are modeled. Such distributions are useful for modeling fatigue crack initiation and propagation.