X-ray diffraction study of a Nd 3 Ga 5 SiO 14 crystal at 295 and 90 k and the structural basis for chirality

摘要: An accurate X-ray diffraction study of a Nd3Ga5SiO14 crystal (sp. gr. P321, Z = 1) has been performed using repeated data sets collected on diffractometer equipped with CCD area detector at 295 and 90 K. The asymmetry the disorder in atomic positions is described two alternative ways: terms anharmonic displacements (at K R/wR 0.80/0.92%; 0.82/0.76%) split model 0.85/0.97%; 0.80/0.74%). analysis probability density function finding an atom particular point space shows that most atoms unit cell are asymmetrically or highly anisotropically disordered vicinity their sites. Electron regions for cations anions form pseudohelices were found. Such mimic screw axis symmetry responsible chirality structure.