Search results for "REFINEMENT"

Template induced crystallization of biominerals on self-assembled monolayers of alkylthiols

1998

Abstract We have studied the templated crystallization of the three polymorphs of calcium carbonate on self-assembled monolayers of ω -substituted alkylthiols on gold surfaces. Our interest has been to model biomineralization processes by examining the effect of structured organic templates on heterogeneous nucleation at the inorganic–organic interphase. The crystallization of the three polymorphs was carried out from solution at two different temperatures. The crystals that were formed on the surface were examined using scanning electron microscopy. Phase quantification was achieved through Rietveld analysis of the X-ray diffraction profiles. This study provides significant clues on factor…

Spectral WENO schemes with Adaptive Mesh Refinement for models of polydisperse sedimentation

2012

The sedimentation of a polydisperse suspension with particles belonging to N size classes (species) can be described by a system of N nonlinear, strongly coupled scalar first-order conservation laws. Its solutions usually exhibit kinematic shocks separating areas of different composition. Based on the so-called secular equation [J. Anderson, Lin. Alg. Appl. 246, 49–70 (1996)], which provides access to the spectral decomposition of the Jacobian of the flux vector for this class of models, Burger et al. [J. Comput. Phys. 230, 2322–2344 (2011)] proposed a spectral weighted essentially non-oscillatory (WENO) scheme for the numerical solution of the model. It is demonstrated that the efficiency …

Fine-Mesh Numerical Simulations for 2D Riemann Problems with a Multilevel Scheme

2001

The numerical simulation of physical problems modeled by systems of conservation laws can be difficult due to the occurrence of discontinuities and other non-smooth features in the solution.

Adaptive mesh refinement techniques for high-order shock capturing schemes for multi-dimensional hydrodynamic simulations

2006

The numerical simulation of physical phenomena represented by non-linear hyperbolic systems of conservation laws presents specific difficulties mainly due to the presence of discontinuities in the solution. State of the art methods for the solution of such equations involve high resolution shock capturing schemes, which are able to produce sharp profiles at the discontinuities and high accuracy in smooth regions, together with some kind of grid adaption, which reduces the computational cost by using finer grids near the discontinuities and coarser grids in smooth regions. The combination of both techniques presents intrinsic numerical and programming difficulties. In this work we present a …

Structural Modifications of Rb<sub>3</sub>RE(PO<sub>4</sub>)<sub>2</sub> Phases (RE = La, Gd, Y)

2001

Cation Distribution in Ferrites with Spinel Structure Measured by Anomalous Powder Diffraction

1998

The Influence of User-Selected Models on the Results of the Rietveld Refinement of the LaOCl Structure

1998

ChemInform Abstract: Crystal Structure and Magnetic Properties of α-Mn(H2PO2)2× H2O.

2010

Abstract The crystal structure of α-Mn(H2PO2)2·H2O has been refined from X-ray powder diffraction data. The cell is monoclinic (space group P21/c, Z − 4) with α = 7.8601(3) A , b = 7.4411(3) A , c = 10.7717(4) A and β = 102.859(2)°. The structure was refined with the Rietveld refinement principles, using as starting model the parameters of the presumably isostructural compound Zn(H2PO2)2·H2O. The structure can be described as being formed by dimeric entities Mn2O2 of edge-sharing manganese octahedra. Each group is linked through Mn-O-P-O-Mn bridges to four other groups, resulting in a three-dimensional network. The thermal variation in the susceptibility shows a sharp peak at T = 6.5 K and …

Powder X-ray diffraction data for potassium silver thiocyanate, AgK(SCN)2 and dipotassium silver thiocyanate, AgK2(SCN)3

2002

Previously unpublished powder X-ray diffraction data for potassium silver thiocyanate, AgK(SCN)2 and dipotassium silver thiocyanate, AgK2(SCN)3 are presented. F30 values for AgK(SCN)2 and AgK2(SCN)3 are 80(0.0075, 50) and 53(0.0089, 63), respectively. The Rietveld refinement of the patterns is also performed. For AgK(SCN)2Rp=6.98, Rwp=11.84, and RBragg=2.9. For AgK2(SCN)3Rp=7.22, Rwp=10.79, and RBragg=5.0.

High-pressure crystal structure, lattice vibrations, and band structure of BiSbO4

2016

The high-pressure crystal structure, lattice-vibrations HP crystal structure, lattice vibrations, and band , and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides. These experiments also give information on the pressure dependence of the unit-cell parameters. Calculations properly describe the crystal structure of BiSbO4 and the changes induced by pressur…