This is the fourth in a series of papers on Rietveld materials characterisation metrology presented at recent Denver X-ray Conferences [refs 1-3]. Reference 3 examined the management of the zero-point and specimen displacement corrections in extracting lattice parameters from BraggBrentano x-ray diffraction data by Rietveld analysis. This paper emphasises the importance of pre-determining the z...

In chapter 10 migration is described in terms of double focussing. In chapter 11 focussing in emission is used to synthesize common focus point gathers (CFP gathers). By comparing aCFPgather with its related focussing operator velocity errors can be detected and the focussing operator can be corrected (Berkhout and Rietveld (1994), Rietveld and Berkhout (1994) , Berkhout (1992), Rietveld and Th...

The paper addresses requirements for achieving Rietveld phase composition analysis (PCA) accuracy in the vicinity of 1% by weight with particular reference to scale factor precision. It is proposed from a statistical analysis that the target for scale factor estimated standard deviation (esd) should be in the vicinity of 0.2% relative, with additional targets being assumed for the ZMV factors, ...

In this article the authors aim to offer some practical advice for phoneticians being confronted with a voice parade request for the first time, by providing a detailed description of a parade carried out successfully in the UK. The methodology used in this parade is based on a number of studies on earwitnesses carried out since the 1990s. However, it primarily builds on the work by Nolan [5] f...

Global optimisation methods of structure determination from powder diffraction data have risen to prominence in a relatively short space of time and they now constitute a key approach in the examination of polycrystalline molecular organic materials. A correctly formulated global optimisation approach may be regarded as a "global Rietveld refinement" that is capable of delivering accurate cryst...

Y(2)GeO(5) (yttrium germanium penta-oxide) was synthesized by solid-state reaction at 1443 K. The arrangement, which has monoclinic symmetry, is isostructural with Dy(2)GeO(5) and presents two independent sites for the Y atoms. Around these atoms there are distorted six-coordinated YO(6) octa-hedra and seven-coordinated YO(7) penta-gonal bipyramids. The YO(7) polyhedra are linked together, shar...

Simulations of 29Si and 23Na MAS NMR spectra indicate the presence of differing proportions of two polytypes and a third phase in three samples of penkvilksite, Na4Ti2Si8O22•5H2O. The most abundant peaks are assigned to the 2O and 1M polytypes, and a third set of peaks are provisionally assigned to a proposed 2M polytype. The quadrupolar interaction parameters for 23Na, Cq and , were calculated...

The structural evolution of nanocrystalline TiO2 was studied by X-ray diffraction (XRD) and the Rietveld refinement method (RRM). TiO2 powders were prepared by the sol-gel technique. Post annealing of as-synthesized powders in the temperature range from 500 degrees C to 800 degrees C under air and argon atmospheres led to the formation of TiO2 nanoparticles with mean crystallite size in the ran...