Decagonite, Al71Ni24Fe5, a quasicrystal with decagonal symmetry from the Khatyrka CV3 carbonaceous chondrite
Decagonite, Al71Ni24Fe5, a quasicrystal with decagonal symmetry from the Khatyrka CV3 carbonaceous chondrite
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DOI：
10.2138/am-2015-5423
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发表时间：
2015-10-01
影响因子：
3.1
通讯作者：
Steinhardt, Paul J.
中科院分区：
文献类型：
--
作者：
Bindi, Luca;Yao, Nan;Steinhardt, Paul J.
十方石是继二十面体(Al63Cu24Fe13)之后的第二个天然准晶，也是第一个表现出结晶学禁止的十方对称性的准晶。在哈提尔卡陨石的一个颗粒(编号为126)中发现了直径达60微米的稀有碎片，这是一种CV3碳质球粒陨石。陨石颗粒含有撞击期间压力和温度不均匀分布的证据，其中部分陨石至少达到5 Gpa和1200℃。十石石与含铝树绿岩、透辉石、镁橄榄石、铝辉石、斜辉石、霞石、柯石英、镍黄铁矿、含铜硫铁矿、二十面体石、哈提夫石、泰安石、含铝蛇纹岩和硬锰矿共生。由于十方石的尺寸非常小，无法确定这种矿物的大多数物理性质。平均七次电子探针分析(从三个不同的碎片获得)得出了以100个原子为基础的公式Al70.2(3)Ni24.5(4)Fe5.3(2)。结合透射电子显微镜和单晶X射线衍射研究揭示了十方准晶的明显特征：尖峰排列成10倍对称性的直线，以及垂直于10倍方向的周期图案。对于准晶，根据定义，其结构不能简化为单一的三维晶胞，因此既不能给出晶胞参数，也不能给出Z。可能的空间群是P10(5)/Mine，就像合成的A(17)Ni(24)Fe(5)一样。最强的五条粉末衍射线[d in埃(i/i-0)]是：2.024(100)，3.765(50)，2.051(45)，3.405(40)，1.9799(40)。这种新矿物已获得IMA-NMNC委员会(IMA2015-017)的批准，并因其结构的10倍对称性而被命名为十方石。第二个天然准晶的发现揭示了凝聚态物理学家对准晶稳定性和稳健性的长期争论，并表明矿物学可以继续给我们带来惊喜，并对其他学科产生强大的影响。
Decagonite is the second natural quasicrystal, after icosahedrite (Al63Cu24Fe13), and the first to exhibit the crystallographically forbidden decagonal symmetry. It was found as rare fragments up to similar to 60 mu m across in one of the grains (labeled number 126) of the Khatyrka meteorite, a CV3 carbonaceous chondrite. The meteoritic grain contains evidence of a heterogeneous distribution of pressures and temperatures that occurred during impact shock, in which some portions of the meteorite reached at least 5 GPa and 1200 degrees C. Decagonite is associated with Al-bearing trevorite, diopside, forsterite, ahrensite, clinoenstatite, nepheline, coesite, pentlandite, Cu-bearing troilite, icosahedrite, khatyrkite, taenite, Al-bearing taenite, and steinhardtite. Given the exceedingly small size of decagonite, it was not possible to determine most of the physical properties for the mineral. A mean of seven electron microprobe analyses (obtained from three different fragments) gave the formula Al70.2(3)Ni24.5(4)Fe5.3(2), on the basis of 100 atoms. A combined TEM and single-crystal X-ray diffraction study revealed the unmistakable signature of a decagonal quasicrystal: a pattern of sharp peaks arranged in straight lines with 10-fold symmetry together with periodic patterns taken perpendicular to the 10-fold direction. For quasicrystals, by definition, the structure is not reducible to a single three-dimensional unit cell, so neither cell parameters nor Z can be given. The likely space group is P10(5)/mine, as is the case for synthetic A(17)Ni(24)Fe(5). The five strongest powder-diffraction lines [d in angstrom (I/I-0)] are: 2.024 (100), 3.765 (50), 2.051 (45), 3.405 (40), 1.9799 (40). The new mineral has been approved by the IMA-NMNC Commission (IMA2015-017) and named decagonite for the 10-fold symmetry of its structure. The finding of a second natural quasicrystal informs the longstanding debate about the stability and robustness of quasicrystals among condensed matter physicists and demonstrates that mineralogy can continue to surprise us and have a strong impact on other disciplines.