English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Chiral symmetry breaking in sodium chlorate (NaClO3) crystallization from a solution was reported by Kondepudi et al. (1990) [1]. The chiral NaClO3 crystal has cubic crystal system and space group of P213. When Kondepudi et al. evaporated NaClO3 solution without any mechanical disturbance, they obtained equal numbers of Land D-crystals in the solution. In contrast, from a stirred solution almost only one type of crystals was obtained. This significant bias in chirality is termed as chiral symmetry breaking. Some theoretical models have been proposed for the mechanism of the chiral symmetry breaking, however, the mechanism has not been elucidated yet. To obtain the direct evidence of chiral symmetry breaking, we carried out in-situ observation of the crystallization process by using a polarization microscope. As a result, we found that non-cubic metastable crystals appeared at first, and then, transformed to cubic crystals by a solidsolid phase transition or a solution-mediated phase transition [2]. On the assumption that the metastable crystal is achiral, we conclude that the chirality of NaClO3 crystal arises when the phase transition occurs. However, it is unknown whether the metastable crystal is chiral or achiral because the crystal structure has not been analyzed in the literature till date. Thus, in the present paper, we reported the result of a single-crystal X-ray diffraction experiment for the metastable crystal. The metastable crystal was prepared by drop evaporation method as follows. A drop (6 μl) of a NaClO3 solution saturated at room temperature (293K) was put onto a cover glass. The metastable phase crystallized in the drop as the solution evaporated. After the crystal grew up to 200 μm in size, the drop were replaced with glycerin. Afterwards, the crystal and the drop of glycerin were frozen by liquid nitrogen. The frozen drop is the specimen for the X-ray diffraction experiment. Xray diffraction data was collected in oscillation mode by imaging plate type single-crystal X-ray diffractometer (R-AXIS IV++, Rigaku). To keep specimen frozen during the experiment, we kept the temperature around the specimen at -266±1 K by Cryostream (Oxford). From the X-ray diffraction, we determined the lattice constant, crystal system, and space group of the metastable phase as follows; a=8.42 (Å), b=5.26 (Å), c=6.70 (Å), β=109.71(°), monoclinic, and P21/ a, respectively. These values are very similar to that of NaClO3(I), which was reported as a high temperature phase of NaClO3 crystal in melt growth (a=8.78 (Å), b=5.17 (Å), c=6.83 (Å), β=110 (°), monoclinic, and P21/a) [3]. Therefore, it is highly possible that the metastable phase we obtained from the solution is the same as the NaClO3(I) phase. In addition, we found that the metastable crystal is achiral because a crystal having a space group of P21/a is achiral. From these results, we concluded that chirality of the cubic NaClO3 crystal arises when the phase transition occurs. The achiral metastable crystals have not been considered in the NaClO3 crystallization from the solution. The phase transition from the achiral phase to the chiral phase may lead to a new understanding for the chiral symmetry breaking.

When does the chirality of NaClO3crystals arise in solution growth?

When does the chirality of NaClO₃crystals arise in solution growth?