An improved method to correct observed shift and asymmetric deformation of diffraction peak profile caused by the axial-divergence aberration in Bragg–Brentano geometry is proposed. The method is based on deconvolution–convolution treatment applying scale transform of abscissa, Fourier transform, and cumulant analysis of an analytical model for the axial-divergence aberration. The method has been applied to the powder diffraction data of a standard LaB6 powder (NIST SRM660a) sample, collected with a one-dimensional Si strip detector. The locations, widths and shape of the peaks in the deconvolved–convolved powder diffraction data have been analyzed. The finally obtained whole powder diffraction pattern ranging from 10° to 145° in diffraction angle has been simulated by the Pawley method applying a symmetric Pearson VII peak profile model to each peak with ten background, two peak-shift, three line-width, and two peak-shape parameters, and the Rp value of the best fit has been estimated at 4.4%.

A method to remove small CuKβ peaks and step structures caused by NiK-edge absorption as well as CuKα2 sub-peaks from powder diffraction intensity data measured with Cu-target X-ray source and Ni-foil filter is proposed. The method is based on deconvolution–convolution treatment applying scale transform of abscissa, Fourier transform, and a realistic spectroscopic model for the source X-ray. The validity of the method has been tested by analysis of the powder diffraction data of a standard LaB6 powder (NIST SRM660a) sample, collected with the combination of CuKα X-ray source, Ni-foil Kβ filter, flat powder specimen and one-dimensional Si strip detector. The diffraction intensity data treated with the method have certainly shown background intensity profile without CuKβ peaks and NiK-edge step structures.

Four series of small parasite peaks observed in powder diffraction data recorded with a Cu-target X-ray tube and a Ni filter on the diffracted beam side in Bragg–Brentano geometry are investigated. One series of the parasite peaks is assigned to the tungsten Lα-emission. Other three types of the parasite peak series are likely to be caused by the K-emissions of Ni, but the peak locations are deviated from those predicted by the Bragg's law. An empirical formula to locate the parasite peaks and a method to remove them from observed powder diffraction data are proposed. The method is based on the whole-pattern deconvolution–convolution treatment on the transformed scale of abscissa. The parameters optimized for the diffraction data measured for Si powder has been applied on treatment of the data of LaB6 powder recorded under the same experimental conditions. It has been confirmed that the parasite peaks in the observed data can effectively be removed by the deconvolution treatment with parameters determined by a reference measurement.

RMC simulation of the experimental structure factor was successfully applied to generate a reliable 3-dimensional atomic configuration. Several partial atomic pair correlation functions, like the g SiO (r), g BO (r), g OO (r), g SiSi (r), g SiB (r), g NaO (r), g BaO (r), g ZrO (r) According to the cosmochemical arguments and the seismological data, the Earth's core must contain some light elements. However, the nature of the light element is still uncertain, and the major proposed candidates have been C, Si, O, H, or S. Therefore, it is important to understand the phase relationships of iron alloys at high pressures and high temperatures. In this study, we conducted high-pressure experiments and ab inito calculations to investigate the phase transitions and the physical properties of iron sulfide. In the case of highpressure experiments, the laser-heated diamond anvil cell combined with the synchrotron X-ray diffraction technique was used [1]. We also used the first-principle calculations to investigate the magnetic property of highpressure phase, which was discovered in the high-pressure experiments [2]. According to previous studies at ambient temperatures, FeS exhibits the following sequence of highpressure phase transitions: troilite (FeS-I), low-P MnP phase (FeS-II), monoclinic phase (FeS-III). In our highpressure experiments, we confirmed that the monoclinic phase was stable up to 40 GPa. Above 40 GPa, the sample was heated to 1000-2000 K to induce the phase transition. After heating, a new high-pressure phase (high-P MnP phase) was observed. This high-P MnP phase (FeS-VI) remained stable at pressures higher than 120 GPa. We found a significant discrepancy between low-P MnP and high-P MnP phases. The discontinuities for the unit cell volume and the cell parameters between two phases were observed. As the structure of low-P MnP phase is identical to that of high-P MnP phase, these discontinuities indicated that an unknown type of phase transition must occur. Next, we investigated the magnetic properties and the spin configurations of these phases using the ab inito calculations. Previous study [3] confirmed that the low-P MnP phase was antiferromagnetic state. The same results were confirmed in our calculations. We also calculated the non-magnetic state for the MnP structure. The calculated results showed that the non-magnetic MnP structure was more stable than anti-ferromagnetic MnP structure at high pressures. The volume and cell parameters of nonmagnetic MnP structure were in good agreement with those of high-P MnP phase observed in our experiments. Therefore, the magnetic transition of the MnP structure occurred at high pressures. The high-pressure stability limit of the high-P MnP phase was also investigated. We found that the phase transition from the high-P MnP phase to the CsCl-type phase occurs at about 300 GPa. Thus, the high-P MnP phase is stable at pressures corresponding to the lower mantle and the outer core. In contrast, the CsCltype phase is stable in the inner core. Our new findings can c...

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