Geng Xu, Wen Bin, Fan Changzeng
State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
IUCrdata. 2020 Oct 27;5(Pt 10):x201412. doi: 10.1107/S2414314620014121. eCollection 2020 Oct.
The monoclinic η-phase in the binary Al-Cr system was initially named by Bradley & Lu [Bradley & Lu (1937 ▸). . , 319-337] as having the composition AlCr (Al:Cr ratio = 5.5:1). Its crystal structure was later refined [Cao & Kuo (2008). , 30, 319-337] to have a slightly lower Al content (Al:Cr ratio = 5.16:1). In the present work, a monoclinic phase with composition AlCr (Al:Cr ratio = 5.04:1) was obtained by high-pressure sinter-ing (HPS) of a stoichiometric AlCr mixture. Structure analysis of this phase, hereafter named η', revealed a close relationship to the previously reported η-AlCr structure, but with different mixed-occupied sites. Five fully occupied sites exhibit refined site occupation factors of 0.899 (5), 0.984 (4), 0.977 (5), 0.946 (4) and 0.945 (4) for the corresponding Al atoms. Moreover, there are no split Al sites in the η'-structure as reported for the η-structure. The refined chemical composition of the η'-phase revealed that it comprises two Al atoms fewer and two Cr atoms more than the previously reported η-AlCr phase.
二元Al-Cr体系中的单斜η相最初由布拉德利和卢[布拉德利和卢（1937年▸）……，319 - 337]命名为AlCr（Al:Cr比 = 5.5:1）。其晶体结构后来得到细化[曹和郭（2008年）……，30，319 - 337]，Al含量略低（Al:Cr比 = 5.16:1）。在本工作中，通过对化学计量比的AlCr混合物进行高压烧结（HPS）得到了组成为AlCr（Al:Cr比 = 5.04:1）的单斜相。对该相（此后称为η'）的结构分析表明，它与先前报道的η - AlCr结构密切相关，但混合占据位点不同。五个完全占据的位点对应的Al原子的细化位点占有率分别为0.899（5）、0.984（4）、0.977（5）······此处原文似乎有误，少了几个数字······0.946（4）和0.945（4）。此外，η'结构中不存在如η结构所报道的Al位点分裂情况。η'相的细化化学成分表明，它比先前报道的η - AlCr相少两个Al原子且多两个Cr原子。
