Papers by Keyword: Pair Distribution Function

Abstract: The structure properties of a ferrofluid modeled by a bidisperse system of dipolar hardspheres are studied theoretically for the case of zero external field. Analytical expressions are providedfor the pair distribution function (PDF) and structure factor (SF) to within the first order in numberdensity and the second order in dipole-dipole interaction strength. The influence of the granulometriccomposition on the behavior of the PDF and the position of the first peak of the SF is analyzed.

Abstract: Direct molecule dynamics (MD) simulations have also been performed to study heterogeneous nucleation and growth of iron on C₆₀ molecule. The grown mechanism of this crystallization process was explored. The results indicate that 92 iron atoms attach to C₆₀ molecule surface can form new covalent bond, forming a closed regular icosahedron. More atoms grow in layer to form bigger regular closed clathrate base on the structure of former one. As increase of atoms number, there will appear some crystal faces.

Abstract: In this work, high vacuum (10^-6 Torr) annealed (at 500^°C) samples of the thermoelectric materials Bi₂Te₃ and Sb₂Te₃ were analyzed in terms of local structures and electron density distribution. After annealing, the samples were analyzed for their structural properties using powder X- ray diffraction data. The electron density distribution has been analyzed using the MEM (maximum entropy method) and the precise bonding in Bi₂Te₃ and Sb₂Te₃ has been determined. Since Bi₂Te₃ and Sb₂Te₃ and their combinations are the latest high figure of merit thermoelectric materials, with immediate application in many fields, particularly the electrical power harvesting devices, a study on the local structure of these materials becomes important which has been carried out in this work. Also the particle size variation due to annealing effect is studied and reported and the bond distance between neighboring atoms in bismuth telluride and antimony telluride has been analyzed.

Abstract: In this work, CdS nano particles were synthesized using aqueous precipitation method; This method is simple, fast and can be carried out at room temperature. Various techniques like X-ray powder diffraction and UV-visible absorption spectroscopy are used for the structural characterization like electron density distribution and estimation of inter atomic distances between the atoms of the nano particles. The optical band gap of this material has been determined in order to establish a relationship between energy gap of bulk and nano materials.

Abstract: In this work, lead sulphide has been characterized using X- ray diffraction, SEM, EDX and UV-Visible techniques. X-ray analysis is done by using the Rietveld refinement method of matching the observed and calculated profiles, and then the results obtained from the refinement process are used in finding the electron density distribution by using maximum entropy method (MEM). The local structure analysis of PbS is done by the pair distribution function (PDF). Particle size analysis is done with the use of XRD data, SEM analysis is done in finding the surface structure and EDX in finding the elemental composition of PbS sample. The energy gap of PbS is found from UV-Visible spectrum.

Abstract: The liquid structure of Al-Si hypoeutectic binary alloys with and without the addition of 0.04 wt.% Sr was characterized by diffraction experiments using a high energy X-Ray (Synchrotron) beam source. The diffraction data for all the alloys were obtained at various melt temperatures. Reverse Monte Carlo (RMC) analysis was carried out using the diffraction experimental data to quantify the partial pair distribution function (PPDF). Further, the partial pair distribution function and the liquid atomic structure information were used in a semi empirical model to evaluate the viscosity of these liquid alloys at various temperatures.

Abstract: In order to investigate the atomic structure of sputtered-deposited Fe76Tb24 amorphous film, we performed X-ray anomalous scattering (XAS) measurements at two energies near the Tb K-absorption edge using the synchrotron-radiations (SR). The total, Tb and Fe environmental pair distribution functions (PDF's) of the amorphous film were obtained from the normalized scattering intensities after the corrections for the structural analysis. The coordination numbers were calculated from the area under the fitted PDF profiles multiplied by 4πr 2 and near-neighbor distances were estimated from the positions of the peaks of the fitted profiles.