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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Transition from the incommensurately modulated structure to the lock-in phase in Co-akermanite.
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Transition from the incommensurately modulated structure to the lock-in phase in Co-akermanite.

机译：在共钙锰矿中从无比调制的结构过渡到锁定相。

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摘要

The adaptation of the incommensurate structure modulation in Ca(2)CoSi(2)O(7) (dicalcium cobalt disilicate) single crystals to decreasing temperature has been examined using in situ high-resolution transmission electron microscopy and electron diffraction. The transition from the incommensurate to the commensurate lock-in phase of Co-akermanite exhibits a pronounced hysteresis of a highly strained metastable state with a characteristic microdomain morphology. A network of domain walls surrounding single orientation domains develops out of the room-temperature tartan pattern, the domains increase in size and their alignment changes from crystallographic to random. At 100 K the phase transition becomes almost complete. In parallel, the evolution of the modulation structure can be described by a change from a loose arrangement of octagonal tilings into a close-packed configuration of overlapping octagons in the commensurate low-temperature lock-in phase. Thereby, the octagon represents the ordered distribution of low-coordinated Ca clusters within a nanodomain extending over 4 x 4 subunits, on average [Riester et al. (2000). Z. Kristallogr. 215, 102--109]. The modulation wavevector was found to change from q(1,2) = 0.295 (a* +/- b*) at 300 K to q(1,2) = 0.320 (a* +/- b*) at 100 K.
机译：Ca（2）CoSi（2）O（7）（二硅酸二钙钴）单晶中不相称的结构调制对降低温度的适应性已使用原位高分辨率透射电子显微镜和电子衍射进行了检查。共钙钛矿从不相称过渡到相称的锁相阶段，表现出高应变的亚稳态的滞后现象，并具有特征性的微区形态。围绕单一取向域的域壁网络从室温的格子呢图案中发展出来，域的大小增加，它们的排列从晶体学变为随机。在100 K时，相变几乎完成。并行地，调制结构的演变可以通过在相对应的低温锁定阶段从八角形平铺的松散排列变为重叠的八边形的密集排列配置来描述。因此，八角形代表平均低于4 x 4个亚基的纳米域内低配位Ca簇的有序分布[Riester等。 （2000）。 Z. Kristallogr。 215，102--109]。发现调制波矢量从300 K时的q（1,2）= 0.295（a * +/- b *）变为100 K时的q（1,2）= 0.320（a * +/- b *）。

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