The multiple-diffraction effect in accurate structure-factor measurements of PtP₂crystals

Abstract

Accurate X-ray intensities of a PtP2 crystal were measured with the multiple-diffraction effect avoided by using the ~b rotation of the crystal around the scattering vector. The results were compared with those of a measurement made without avoiding the effect. The extinction parameters were more isotropic and the peaks of the deformation density were significantly smaller when multiple diffraction was avoided. In the measurement made without avoiding the effect, the number of structure factors affected by * To whom correspondence should be addressed.© 1994 International Union of Crystallography Printed in Great Britain -all rights reserved more than 1% was 403 from 936 reflections measured. Of 272 strong reflections with sin0/A < 0.6 A-1 and Fob s > 200, 27 reflections were affected by more than 1%. These facts, as well as the smaller R values, indicate that the multiple-diffraction effect cannot be neglected in electron-density studies of crystals including heavy atoms. To assess the intensity fluctuation calculated in the present study, the intensities of 200 reflections were measured at intervals of 0.5 c from 0 to 180 ° in ~0 and compared with the calculated values. The variations of the measured and calculated intensities with ~ correspond to each other, which indicates that the present method can Acta Crystallographica Section A ISSN 0108-7673 © 1994KIYOAKI TANAKA et al. 247be used effectively to identify the reflections affected significantly by multiple diffraction.

Pd20Pt20Cu20Ni20P20 high-entropy alloy as a bulk metallic glass in the centimeter

“…4). The phases are a mixture of four phases, bct-Ni 3 P, two types of fcc's with formulae of Ni 2 Pd 2 P and fcc-(Ni,Pd) [22], and a cubic phase of PtP 2 [23]. We interpreted that the peak shifts from the original data can occur in latter three phases, but not for the bct-Ni 3 P phase due to the solubility of elements.…”

“…We interpreted that the peak shifts from the original data can occur in latter three phases, but not for the bct-Ni 3 P phase due to the solubility of elements. The changes in lattice constants that cause shifts in the peak positions are approximately þ0.008, þ0.0072, and þ0.005 nm for Ni 2 Pd 2 P, fcc-(Ni, Pd), and PtP 2 [23], which has reported lattice constants of 0.3806, 0.3686, and 0.5694854 nm, respectively. Thus, the ratios of the expansions of the lattice constants account for 2.1% for the Ni 2 Pd 2 P, 2% for the fcc-(Ni,Pd), and 0.88% for the PtP 2 phases.…”

4f-Electron Density Distribution in Crystals of CeB6 at 165 K and its Analysis Based on the Crystal Field Theory

“…The smaller the crystal, the less pronounced the systematic errors due to absorption, extinction and MD. As MD occurs frequently and its intensity perturbation is very significant for crystals containing heavy atoms, it was avoided using the ~p-scan method (Tanaka, Kumazawa, Tsubokawa, Maruno & Shirotani, 1994). There were more than one secondary reflection for every ¢.…”

Trineodymium(III) pentairon(III) dodecaoxide, Nd3Fe5O12

“…Data collection: AFC-5, specially designed for PF-BL14A (Rigaku Corporation, 1984) and IUANGLE (Tanaka et al, 1994). The title compound, Nd 3 Fe 5 O 12 (NdIG), was difficult to be grown.…”